aj mccormack and son

Drainage - Page 02
The Brew Cabin


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Forum Question Draining garden into FW - Frank - 1 Mar 2002
My back garden is very poor quality soil which is shallow on top of shale then clay, it is always waterlogged. Can I drain it into the foul water system.


forum answer Tony McCormack - 1 Mar 2002
Is there no surface water system present, Frank? Draining into the Foul is a last resort and needs to be 'trapped' to prevent bad smells escaping.

Have you read the FAQ on Improving Clay Soil? The suggestions therein are much cheaper and easier than installing land drainage.

Forum Question Garden soakaway - Jason Percival
Hi. I have a garden that used to have grass on it but it is now so wet that as soon as you stand on it you just slip and slide ripping off the grass, it measures approximately 30ft by 18ft and slopes diagonally from the front right to the rear left. I want to put a drainage system in to sort it out. What would be the best system to use to sort it out?

Jason Percival

forum answer Tony McCormack
Land drainage is a last resort when trying to improve the drainage in a garden. Have a look at the FAQ link in the Land Drainage section first. If you can improve the condition of your soil, it will not only rectify the drainage problem, it will give you a better garden.

However, if drainage seems to be to only solution, you should use a collector-type drain, but bear in mind that you have to drain it to somewhere. Have you an outfall in mind?

Jason Percival What I had in mind to use as an out fall was to dig a hole 3' square and about 3' deep with the sides built from block and then filled with gravel. Would this be ok?

Or do you have a better sugestion?

Tony McCormack
What you are proposing is a soakaway, but you've already said that the garden is waterlogged, so to where would a soakaway drain? The answer is that it won't - it will just fill with groundwater and all your work will be for naught.

A soakaway can only work in well-drained ground, which you haven't got. What you need is a Surface Water drain that you can connect to, or a ditch, stream, river etc, to which you can outfall.

Read the section on soakaways for a fuller understanding. smiley

Forum Question Soakaway construction - Martin Lloyd - 1 Mar 2002
I need to construct 4 soakaways to handle roof drainage of approx approx 180m², plus a bit for surrounding patios. Using the calculations on your site, I guess that I need say 3 to 4 cubic metres of soakaway, say 0.85m³ each.

I chased up the Polypipe Civils plastic solution but was a bit taken aback that the price is not far short of £400+VAT each (which seems an incredible price for a bit of plastic with holes in!), so I started investigating the concrete sections method.

I tried several builders merchants and landscape materials suppliers but I have not been able to find any supplier that has ever heard of special concrete soakaway sections.
I got some prices from Jewson for inspection chamber sections and decided that the best solution would be to use 600 x 450 x 225 sections separated by engineering bricks 2 abreast, 5 sections deep, so I needed 40 sections overall. The next problem is that the builders merchants Jewson & Travis Perkins dont tend to stock more than a handful of these and are unable to obtain them unless they order 24 tonnes from the manufacturers! Some of the smaller suppliers would be able to get them but the price shoots up to about £13.50 each plus VAT. I can get some 150 deep sections from Travis Perkins for about £7 each but I think that these may be to small and unstable

What do you recommend, 225 deep sections at £13 each or 150 deep sections at £7 each, or is there a better solution?

I have a guy coming with a mini digger next week and I need to make a decision fast!

Martin Lloyd

forum answer Tony McCormack
Concrete soakaway sections are manufactured by Marshalls and by Milton Concrete - see links section for contact details. However, they are trade suppliers and may not be able to meet a short order.

As for the simple plain concrete sections, try a Civils Merchant, rather than a Builders' Merchant. Jewson and TP tend to stock only the most commonly used items in the building trade. For owt a bit out of the ordinary, a smaller local co is often a better source. If you have a branch of Burdens locally, or, if you live in the NW and can contact Cooper Clarke in Bolton, they have HUGE stocks of concrete sections.

I'd always go for the larger sections. 300mm is even better than 225mm and really shouldn't be all that hard to source. I know that I could get as few or as many as I needed at less than 48 hrs notice. Whereabouts are you?

Martin Lloyd Tony, thanks for the advice about 300mm sections being preferable - I shall avoid the 150mm sections. One concern I have about larger sections is will I be able physically handle them? Do you have any idea on the weight of a 600 x 450 x 300 section?

From a functional viewpoint a 600 x 900 x 300 woul be ideal but I doubt I could handle one of these. I live between Worcester & Kidderminster.

Great site!

Tony McCormack
The data sheet from Milton Concrete quotes a 600x450x300mm section @ 85Kg, but they are cumbersome and quite rough-cast, so need careful handling.

That part of the SW Midlands is not an area I know too well, so I can't suggest any local Civils Merchants. However, it might be worth giving Cooper Clarke a call, as they do deliver down there or they may well be able to put you on to a local Merchant with whom they have a reciprocal arrangement.

Cooper Clarke Drainage Division - 01204 862222
Milton Concrete - 01795 425191

Martin Lloyd I tried the Oldbury branch of Burdens and they advised me that they only did 450x600x150's and that I would have to double them up. I tried Cooper Clarke in Bolton as suggested and they gave me the number of their Coventry depot. Coventry told me that they did not normally stock 450x600x300, but they were able to bring them in specially from the South of England although this incurred extra freight costs which were loaded into the price offered. For the moment I have decided to fall back on the 450x600x150's sections offered by Travis Perkins. At least they should be light enough to handle comfortably!

My latest plan is to use 18 sections per Soakaway, doubled up to create 9 450x600x300's which will be arranged in 3 columns of 3 separated by engineering bricks. Total approx dimensions of 600 wide x 1500 long x 1000 deep (plus membrane & gravel surround), then capped off with some 900x600x50 Slabs plus a layer of 100mm reinforced concrete above and 150mm plus of topsoil above that.

Do you think that the structure would collapse if a car was ever driven across it? Also, do you think that 110 plastic drainage pipe between my gutter downpipe and the soakaway which may be only 300mm under a paved surface would be able to withstand light vehicle traffic if encased in concrete?

Tony McCormack I find it odd that 300mm sections aren't available ex-stock. Did you ask about other sizes? You don't have to use 600x450, you could use, say, 750x600.

Your slab cover probably needs to be stronger. I'd go for 150mm thick, with A193 mesh top and bottom, and then use a C30 concrete vibrated into place. Alternatively, you might be able to get a 'biscuit' ex-stock from CC or Burdens.

The 110mm plastic pipe will definitely need encasing. Even a vc pipe at that shallow depth should be encased if it is to be trafficked.

Forum Question Soil Stack Connect - GeoffH - 21 Mar 2002
Hi Tony,

I have to replace a soil stack (from upper floor to ground) on a side wall of the house. It connects at ground level to a shallow inspection chamber - and I mean literally at ground level, as there is only enough depth for a single 90 degree bend connector which goes directly into the chamber (because it is close to the house wall as well....) where it is mortared in place as the inlet. This bend is currently earthenware but the top is broken and I will need to replace it. Can I use a standard plastic soil pipe 90 bend instead? The only earthenware ones I can find are too big/long radius. Will the mortar seal to the plastic, do I need to roughen it and use PVA etc? Any other suggestions?

Geoff Hughes

forum answer Tony McCormack
21 Mar 2002
Hi Geoff,

you can use plasticware if you like, but they tend to be more or less the same dimensions as their vitrified clay cousins. If it fits, it'll do, basically!

Generally speaking, there's no need to roughen the outside of plasticware - it bonds to concrete or mortar well enough. I'd pack all around with a 1:2:4 concrete outside the chamber. On the inside, you can prime with PVA or similar before sealing any joint with a 1:4 mortar and then repairing the benching with grano.

21 Mar 2002
Hi Tony,

Thanks, that makes sense. I thought it might be OK like that, but it's good to have confirmation.


Forum Question What is a French Drain? - Babs - 25 Mar 2002
I have a house which is about 2 years old on a new estate. The position is west facing. The soil is heavy clay! It is very very wet and waterlogged. A couple of people have suggested a "french drain". What do you think? Could this be done? Should it be done? Can we do it ourselves? Would it be expensive?
forum answer Tony McCormack - 25 Mar 2002
Hi Babs,

a French drain is a 'catch-all' term for a land drain. In the trade, there are quite a few different types of land drain, but a French drain is, correctly, a Fin Drain, and you can read about them on the site.

However, what you actually need is probably a collector drain. Have a look at the pics on the Land Drainage page and you'll see what I mean.

It can be done, it's relatively simple, as long as you're fit and active and don't mind hard graft, and you will save a fortune by DIYing as contractors are not overly keen on coming in to residential properties to do this type of job, unless there's more than 50m or so.

Have a read of the page mentioned above, and post back if you've any further queries.

26 Mar 2002
Ok, thanks for that. I'll have a look at what you suggest and come back to you no doubt!
Forum Question Water collecting under floorbaords - Paul - 27 Mar 2002
Hello, I have recently rewired my new house which was built in the 1920s. In the last heavy rain I noticed that water was collecting under the floor at the back wall of the house. The water sat between the back wall and the first brick beam on which the joists sit. I thought that it may be a high water table as the rear garden slopes down to the house and sometimes about an inch of water can sit on the lawn in places. However, I have single storey extension on half of the rear of the house and on the outside wall of that there was a downpipe. This downpipe goes into the ground.

When the water had dispersed and the floor dried, I put a hose pipe down the down pipe for about 20 minutes. I checked under the floor and the water was back. I am not sure how this is happening. Do old houses have soakaways under the house which may have degraded or would there be some other drainage under the house.

There is a drain to the side of the house which takes waste water from the kitchen and downstairs bathroom etc.

I would appreciate your thoughts as I am worried it may be causing damage to my house/foundations etc.


forum answer Tony McCormack - 27 Mar 2002
Do you think the downpipe is the source of the water under the floorboards, Paul? If so, you can check this out by using a drain tracing dye and adding that to the downpipe along with a the hose and see if it turns up under the floor. Yellow might be the best colour to use, although the blue should be easy enough to see with a torch.If it's just a leaking downspout, it could be relatively simple to fix, but you need to establish whether that's the cause, first.

I would strongly suggest you get a builder to look at this. Pre-war houses are pretty much a law unto themselves and it's impossible to say what you might find or what you might not. A soakaway in the sub-floor wouldn't be all that unusual, but there's no way of saying there will/should be one.

Any water hanging under the floorbaords is not only a potential threat to your property, it's a potential health hazard. Get a good local builder, or call the Building Control Officer at your Local Authority. It definitely needs checking out.

Let me know how you get on.

Forum Question Draining heavy clay ground - MikeT - 30 Mar 2002
I have lived in the same detached house for more than 20yrs now and in the last few years have noticed that surface rainwater is taking longer to drain away from behind my home.
The lawn area is some 130ft x 50ft wide and slopes towards the house/back yard (we are common and don't have a patio<S>) its also some 3ft higher than the yard at its closest to the house rising to maybe 4.5ft at its farthest, so its a large area to drain off. The lawn has had a hammering over the yrs from kids on damp days compacting the clay which is only some 6-9inches under the topsoil.

I will be coring the lawn and filling the holes with sharp sand/grit to try and help that drainage soon. I would like to French drain the area but maybe thats over the top and expensive.

Anyway you can see I get quite a bit of water heading towards the yard albeit under the topsoil so you don't see a river running down when its raining hard.

I am thinking of removing the concrete yard and laying patio slabs<G> so with that in mind I dug a 12 inch hole in the yard to see what the drainage was like thro the clay beneath.

It was obvious even after no rain for 4 days that the clay was waterlogged, within 1hr I had ½ inch of water in the hole and still seeping through the clay.

Now there are 2 drain runs and a manhole to the drains all within 15ft of where I dug down, what I don't understand is why the water is collecting in my hole when I would have thought it would have seeped into the shingle or whatever bed that surrounds the drainage pipes underground and followed them to a lower point (like the road).

The existing drains to my home have a 2ft drop (fall) from rear to front of house inspection pits so I would have thought it would all drain away easily.

I guess I need to dig a trench of some sort, say 1ft square through the clay under the yard and fill it with something to aid the drainage and point this towards the real drains maybe actually cutting into the pit nearest with pipework too.

So my questions are:
Is my 1ft square hole in the clay filling (its got 3inches of water in now after 24hrs) because of water pressure in the clay forces it to the open hole where only atmospheric pressure is present? or is this likely to be the water table?

Why doesnt the water drain away through the clay to my existing drainage trenches which should have been surrounded with shingle of some sort and would I think have formed a ready made course for the water to follow to the road and away?

Could I cheat a bit<S> and just trench out 1sq ft across the yard below the raised lawn, fill with large gravel and do the same to a point where my existing drains are bedded in?

Sorry this is so long but I wanted to give as much info as I could.
I do hope it formats ok as I cut and pasted some.

Best regards

forum answer Tony McCormack - 31 Mar 2002
MikeT asked....

Is my 1ft square hole in the clay filling because of water pressure in the clay forces it to the open hole where only atmospheric pressure is present? or is this likely to be the water table?

It's the same thing, Mike - that must be the water table. It can rise and fall through the year, but at the moment, it's higher than the base of your test hole.

Why doesnt the water drain away through the clay to my existing drainage trenches which should have been surrounded with shingle?

There's no guarantee that pipe bedding was used when the drains were originally installed. If it was, it may well have silted-up by now. Alternatively, if the clay is impermeable, it would make little, if any, difference.

Could I cheat a bit<S> and just trench out 1sq ft across the yard below the raised lawn, fill with large gravel and do the same to a point where my existing drains are bedded in?

That's what we call an interceptor drain. You could try that but I would strongly recommend you connect to the existing SW system rather than tap into the original drain cutting and hope for the best. If you've got the ground open, you might as well make a proper job of it; if you take the lazy option and it doesn't work out, it means digging out again and making a new connection in very, very wet ground.

Further, if you make a proper connection at this stage, and then install an interceptor drain, any future additions to the interceptor are a comparative doddle - you just tap into the existing interceptor with the new lengths, safe in the knowledge that a proper connection to the SW system is in place and that any groundwater collected/intercepted is being disposed of properly, not just shifted to another part of the garden. smiley

31 Mar 2002
Thanks for the reply Tony, I might have bitten off more than I can chew here.
The main purpose of digging the hole was to see what was down there in order to figure what drainage I needed to do before laying a patio.
Now finding a water table just 8.5" from the yard surface has me worried for my home foundations, the detached house was built in 1962 on clay before the latest regs for foundations on clay.
Should I be worried (i am already) about the water?

If I can dig down 1ft and get that much water at the rear of my home, then at the front which has a lower ground level it must be even nearer the surface?

Unless of course I am being missled by the raised rear garden draining into the hole.

Perhaps I ought to get a builder in, now there is a frightening thought. sulk


Tony McCormack
1 Apr 2002
Mike writted....

Now finding a water table just 8.5" from the yard surface has me worried for my home foundations, the detached house was built in 1962 on clay before the latest regs for foundations on clay.
Should I be worried (i am already) about the water?

I really wouldn't worry about it too much, Mike. The water table fluctuates and your foundation will be more than capable of withstanding ground water.

And a water table isn't always 'level' - it can follow the lie of the land and actually be lower in your front garden than it is at the back!

You could call in a builder, but bear in mind that they would be dead set on selling you summat, if only to cover their call-out costs, and other than the interceptor drain I mentioned, there's nowt you really need.

If you feel you could install that yourself (it's really not that difficult), you'll probably find it ameliorates most, if not all, of your problems.

Trust me, I'm a groundworker!  smile

1 Apr 2002

>>If you feel you could install that yourself (it's really not that difficult), you'll probably find it ameliorates most, if not all, of your problems. Trust me, I'm a groundworker!  <<

Trust a groundworker who not only uses words I cant pronounce let alone know the meaning of without getting the dictionary out.....and who posts such words of reassurance on April fools day!.....Hmmm... wink

My next door neighbour just made me chuckle, the local council insisted he put in a soakaway for the downpipe off his roof when he had his extension built!! You already know what soil we have<S>

Also he says that when it rains heavily his patio (yes patio, he doesnt have a back yard) gets so much water on it that it runs away though his garage rear doors and out the front to the road.

Guess who's patio I will be draining with my new drains?


Tony McCormack
1 Apr 2002
Get the neighbour to chuck in with you, Mike! The two of you should be able to rattle in a new interceptor drain across both properties over a weekend, and then you won't feel as bad about draining their patio. smiley

If the LA are recommending a soakaway, it suggests that you have no SW system or that you have a combined system and an overworked ETW. Given that you're reporting saturated ground, impermeable clay and a shallow water table, I'm surprised they're recommending a soakaway in the first place!

Do you know if you have a SW system?

1 Apr 2002
The neighbour has just submitted plans for another dropped kerb for a second driveway so he's fully stretched at the moment and would be non too pleased about pulling up his newish patio to lay drains.
My neighbour was equally suprised too about the soakaway, it was full of water before they managed to finish it and totally usless afterwards.

Yes, our system is combined, storm and sewer (not dual) I have 1 cover behind the house and one in front.
Unfortunatley the one in front has all of next doors foul and storm coming into it befoe it goes off to the road from mine.

I think I will try and combine a yard gulley or 2 for surface water removal, with this in mind, should I use pipe thats perforated all round or half perf'd and place it "holes up" in the trench?
Will I also need to trap the pipe as it enters the inspection hole? or will the yard gullies own traps be enough?

Heck this thread is getting long! smiley


Tony McCormack
1 Apr 2002
If you'e installing a yard gulley, you need a non-perforated pipe, really, but, if you want to use a perforated, make sure it's properly surrounded by 100mm (minimum) of clean pipe bedding (A10 or similar) and a filter membrane, such as Terram1000. You could use a fully perforated pipe, but I'd prefer to use a half-perf with holes upwards.

The important thing is to ensure a trapped gully is used to prevent smells escaping from the combined system, and incorporate a sealed rodding eye if you're not breaking into an existing Inspection Chamber. A trap before the IC is not essential as long you're using properly trapped gullies, or a P-trap hopper arrangement.

21 Apr 2002
Well after several quotes for my drains and removal of all the old concrete from my yard and laying a new patio using 450x450 flags I have agreed a price for a local builder to come and start.
Prices went from £4000 plus down to just around 1K.

You mention Terran 1000 lots but my local builders merchents stock Plantex, as good?

The builders quote states 10mm pea shingle for the drains to be laid in, should I ask him to change this to 20mm? He hasnt quoted to surround in Terran or other but I will be asking him to do so.

I have just cleared a trench behind a garden soil retaining wall that had 2 25mm plastic tubes through it for drainage, I found roots growing in the tubes and they had backfilled behind the wall with old builders rubble, all that did was get blocked with soil.

I want to put say a 80mm tube in there and shingle in a membrain to give it a chance to soak away, do I just puncture the membrain where to tube goes through the wall and push it into the shingle? wont the shingle try to run down the pipe? or do I wrap the open pipe end with membrain?
I thought I saw a diagram of this on your pages somewhere but cant see it now for looking.

I'm worried that roots will force their way between the wall and bag of shingle to get to the pipe if I dont seal it into the membrain.

Thanks again

Tony McCormack
21 Apr 2002
Hi again Mike,

taking your points one at a time....

Plantex is nowhere near as good as Terram 1000. Plantex is a landscape fabric intended to keep bark/gravel etc separate from a sub-grade (ie, the bare earth), or make life hard for weeds; Terram is a geo-membrane and is tested and approved for use as a filter membrane for land drainage.

I have no data sheets for Plantex, but I seem to recall that it's nowhere near as tough as Terram, and therefore there's a real risk of puncturing it, which then compromises the integrity of the drain. Further, when I've seen Plantex on sale, it's always been more expensive than Terram 1000.

You can buy a Terram equivalent online at the Terram Garden website. It's sold as 'Patio Partner'.

The choice between a 10mm and a 20mm is somewhat academic on a small project like this. A 20mm is better, but a 10mm will be ok, as long as it is CLEAN, ie, not mixed with fines.

I'm not sure what you mean about the 'tube' (I think you mean 'pipe') going through the membrane. The membrane is wrapped around the the gravel surrounding the pipe. The pipe and the mebrane don't come into contact with each other. Can you do me a sketch and email it to me?

If you have an open end to your pipeline, that can wrapped in membrane to keep out the gravel, or you can use an end cap.

23 Apr 2002
OK Tony, I have ordered Terran, its more expensive than the other but i'm sure its worth it.

This shift work must be getting to me, I dont seem to have an email addy for you, I have just stuck some quick pics up on a web page of the wall.

C is the concrete base for the wall, B is the silly little pipe they stuck through it and covered with old broken bricks.
I have opened the hole to 80mm plus so I can put a pipe through.
To get as low as possible the pipe will near touch the concrete footing on the soil side. So do I just cut it flush with the brick and then lay membrain and shingle over it, or do I cut into the membrain so my pipe enters it and then tie a bit of membrain round the open end of the pipe to stop stones from entering it.
I didnt intend using perferated pipe, just a bit of 3" rainwater through the wall.
Such a lot of questions for a silly little job! smiley

Thanks again.

Tony McCormack
23 Apr 2002
I think I'm with you, now, Mike. Your plan is to use just a short length of pipe to create a weephole through the wall, is that right? I thought you were laying a land drain along the back of the wall and then bringing it through the brickwork to discharge onto the existing concrete.

So, if you're just using a small 'tail' (as we call it), wrap a length of Terram around the open end of the pipe, then, line the trench with Terram, push the pipe into the hole in the wall, cover with the gravel, then draw the Terram over the gravel to 'warp it', and then back fill with excavated material.

Does that make sense, or do you want a sketch?

23 Apr 2002
Just what I wanted to know Tony, thanks! smiley

The land drain is another project now that is under the concrete yard......


Forum Question Draining a patio - ChrisM - 31 Mar 2002
I've just been levelling a patch of ground outside my conservatory ready for a patio. It's going to be about a 4m square and lies on clay. One side is formed by the house wall and there is a drain pipe running from the roof gutters down the wall and  then  immediately beneath the proposed patio and off in the direction of our lawn. Not sure if it disappears into a soakaway or something else but it is clear and gets rid of the rainwater. This (plastic) drain pipe will be only a few centimetres (perhaps 5cm) below the paving stones. On the assumption that I need to provide drainage for the patio, can I connect in to this plastic pipe or would you recommend I provide seperate drainage?
forum answer Tony McCormack - 1 Apr 2002
I'm not fond of connecting to existing drainage unless I know where it's going. It may be connected to the SW system, if you have one, in which case, there's no problem connecting a new gully to it to enable you to drain the patio.

Do you have a SW system? You could put some drain tracing dye into the candidate pipe and see if it flows through one of the Inspection Chambers on your property.

If it's going to a soakaway, it all depends on how efficient the soakaway is. Although you're only adding a further 16m² of drainage, it could overload the soakaway, causing it to surcharge. Given that you've never experienced any problems with drainage to date, it's a good bet that it would be ok to use, as long as it is a proper soakaway and not just a 'tail'; that is, a pipe that leads into the garden and just dumps the water there.

Can you trace the shallow pipe while you've got the ground open?

2 Apr 2002
Thanks - you're right of course, I really will have to trace this drain further to be certain it can cope. We are in the Fens, so there must be a chance it finds its way to a drainage ditch!
On the assumption that all is well with it's capacity, will the fact that the pipe is so near to the underside of the flags make it difficult to connect in? Having viewed your webpages on this subject I'm pretty sure I will have to connect in at the side of the patio furthest from the house wall. It's tempting to try a linear drain at the foot of the house wall but I don't think I can make the required 150mm below the dampcourse. This is getting more complex than I originally anticipated - but it's really helpful to be able to air my problems in this way.
Tony McCormack
2 Apr 2002
I can't see why connecting to the existing pipeline would be a problem. If the pipe is lower than the base of the flags, then adding a gully should be straightforward. the ribs on the couplings do come up  a bit higher than the rest of the pipe, but it's only 10mm or so.

With regard to the linear drain, what sort of clearance do you reckon you could get between top of drain and dpc? If you can get 100mm, I reckon you'd be ok on such a small project. But, will you be able to get enough fall from the outlet of the Lin drain to the the drain pipe?

8 Apr 2002
I am so glad I sought your advice!
By investigating further I've found that a drain pipe runs parallel to the house wall and hard up against it before connecting to the drain I had previously uncovered which runs away from the house. This latter eventually terminates in a soakaway about 5 metres from the house. The soakaway is loaded with rubble and has plastic sheeting covering it and, as I said before, is able to cope with the current load. What has amazed me is that the entire run of 4 inch pipe (about 6.5m total length) was absolutely full of roots from a nearby leylandii hedge. How any water got through the roots I'll never know. Anyway, I've now got a 6 metre long "serpent" lying on the lawn which is proving quite a talking point amongst the neighbours!  I'm planning to remove the hedge next Winter anyway and I'll just run a short length of new pipe into the same soakaway from a new patio gulley.

I've a new question regarding the bed for the patio but I'll raise that in another forum.

Cheers, Chris

Tony McCormack
9 Apr 2002
Good to have another satisfied customer, Chris. smiley

If there are any other large trees or <spit> Leylandii in the vicinity, you could encase the new pipeline in concrete with flexi-joints (as shown in the drainage section), or you could line the trench with a root-barrier geo-membrane, such as Terram

Forum Question Backfalling Patio - Kieran - 4 Apr 2002
Hi all,
My back garden measures 7m x 9m and I am currently in the process of paving the entire area. The problem is that my garden slopes towards the house, so in order to ensure that the patio slopes away from the house, I have a lot of digging to do. My query is as follows: can I allow the paving to slope towrds the house if I install some type of linear drainage chute into my existing storm water drain?

Thanks in advance,

forum answer Tony McCormack - 4 Apr 2002
Hi Kieran,

the best way of dealing with this sort of scenario is to install a linear drain or a dished channel about a metre or so from the house and make that the low point...

backfalling patio

...if you use a dished channel, you'll need to incorporate a gully at some point, bit that should worl out cheaper (and easier) than using a linear drain.

Note how the paving falls from the house to the channel at around 1:40 and then the rest of the paving backfalls from what was the garden.

Does that make sense?

5 Apr 2002
Thanks Tony,
That's perfect. Just what I had in mind. Forgive my ignorance but do you mind me asking what exactly a 'dished channel' is? Is it just a plastic chute? If so, do you know if it's possible to get covers for these?
Sorry for all the questions!

Best regards,


Just priced some linear drainage systems and they range from 18-20 euros per half metre (12-15 stg). As I need around 7 metres, it makes the job very expensive. Is there a cheaper way to construct the drainage gully? I can shape one out of concrete, but obviously this wouldn't be covered like the linear drainage system.
Thanks again for your help,

Tony McCormack
5 Apr 2002
There's are some illustrations/pictures of dished channels on the Road Kerbs page, but, for a patio, you're probably better off with the Keychannel unit from Marshalls. 200x2200mm and only 50mm deep, they sell at around 6 quid per linear metre (1.20 each).

They are sold in Ireland, as I've seen them used on a relative's property in Co. Wicklow.....


...they come in red, brindle (red/black] and charcoal, and they are a doddle to lay. The 'dish' is only 25mm or so deep.

The larger, 915x250mm units in concrete grey (shown on the Road Kerbs page) cost around 3-4 quid apiece, but are not really patio-friendly.

The B&Q DIY Shed's in the UK are selling a Recyfix linear drain, complete with galvanised steel grating for 10 quid per 1 metre length. There may be something similar in the Republic, but it's a couple of years since I was over and I'm not sure what's available.

Forum Question Storm drainage into flower bed - John D - 10 Apr 2002
My single home contains a downspout that empties onto the driveway and next to a bed that is against the garage. I intend on building a 9" high fieldstone wall on three sides of the bed (the fourth side is the garage) and installing shrubs, etc. Instead of allowing the downspout to empty onto the driveway, I'd like to direct it into the newly enclosed bed and allow a perforated PVC pipe to carry the rain water across the 20' bed. My question to you is...Is this recommended? Will it turn my bed into a slurry? Will it compromise my foundation or garage slab? I'd rather not dig under the new sidewalk or driveway to carry the water away from my house. My plan seemed to be the simplest remedy. Can this be done or am I better off avoiding worse-case-scenerio by allowing it to dump onto the driveway?
forum answer Tony McCormack - 10 Apr 2002
I can't say how effective it would be without knowing the nature of the site, John. If you have a free-draining soil, then the planter bed may be able to cope, but then again, I don't know the area of roof that is being drained, or percolation test data for your area.

In the UK we prefer soakaways or leach fields (which is more or less what you're proposing) to be at least 10 metres away from the property to avoid potential problems with the foundations and/or damp. Things may be different in your part of the world, but I have no experience of practices outside Britain and Ireland.

Also, from your description, it sounds as though you will be piling up earth against the garage wall. This, too, is something we would not do in the UK/RoI.

If you discharge directly onto the driveway, where would the water run to? Back to the house or out to your 'sidewalk'?

Forum Question Un-bridging of DPC - Vince - 13 Apr 2002
My house has a front extension (built many years ago) that sticks out further than my neighbour's (attached) front wall. It has a slate DPC but my neighbour's concrete drive abutts my extension and is about 8 inches above the DPC. He has said that he doesn't mind me cutting some of the concrete away so there is a trench between his drive and my wall.

What can I do with the trench to ensure that my wall stays clear and dry? A surveyor mentioned a "French Drain" is required and said something about pebbles but I've so far been unable to find a definitive solution to this problem. Can anybody help?

forum answer Tony McCormack - 13 Apr 2002
Hi Vince,

this has become something of a FAQ, so I've created a page showing the various ways of resolving this particular problem. Anyway, here's a sketch showing how your partiular situation could be dealt with...

dpc drain

...does that help? Just ask if you need further explanation. smiley


  • The perforated land drain will need to be connected to the SW system or a soakaway at some point.
  • The Terram 1000 membrane  helps prevent the gravel becoming silted-up with crud and whathaveyou over time.
  • The impermeable membrane could be a drainage composite, or you could use bitumen 'tanking' or similar. It could actually be omitted unless there is an exceptional water flow regime and you have regular inundation of this wall.
  • The flag-on-edge ensures the sub-base or sub-grade beneath the existing concrete doesn't fall into the drainage channel. I've shown a 450x50mm pcc flag, but you could use almost anything to suit you taste/pocket. smiley
  • By cutting back into the existing concrete, you give yourself more working space and it can be patched in with fresh concrete or grano once the flag-on-edge is in position.
  • The gravel on top of the permeable membrane could be a decorative type, rather than the larger 20-50mm clean gravel used within the channel as backfill.
13 Apr 2002
Thanks for that. It's exactly what I've been looking for!

Thanks again.

Forum Question Extension Drainage Design - Mike L - 1 May 2002
Hi Tony

First of all I must congratulate you on a BRILLIANT! Site its the best I have seen for us DIY,ers and to think I paid a subscription to a web based home build site that has only a fraction of useful data, I want my money back!

I am in the process of building an extension to the side of the house and am going to scrape down the earth to below DPC in preparation for trenching. As the house is some 70+ years old I was thinking of replacing the combined drainage system for foul /sewerage. The reason being the new garage and kitchen will be built over the drains. The present configuration has a soil pipe and one hopper type drain for the old kitchen and down spout. The Garage will be built around the existing wc soil pipe.

Is it permissable to have a rodding point within a garage or should I be putting in a rodding eye which will have to be further away about 6m near to a P-trap hopper for new kitchen waste water/ rainwater drainage.

Finally, Is it permissable to have the piping cross a foundation currently 900mm, although I,m not sure yet at what depth it will cross at. Do I need place pipe beneath a box or lintel type structure?


forum answer Tony McCormack - 2 May 2002
Hi Mike,

thanks for the compliments. It's good to know that you find the site useful. smiley

Right then, your questions....the Rodding Eye - this is best positioned at the head of a run, so, if you have a line coming up the side of the house, serving the downspout and the Kitchen Waste, then the rodding eye should either be adjacent to the last upstream fitting, or at the end of the straight run.

The key determinant is that you must be able to get to ALL parts of the system with rods. If you have access from downstream via an IC or MH, then a rodding eye might not be essential, but I can only really say what is best if I had a sketch plan of your layout. If you want to send me a sketch, as a gif file or similar, I'll upload it to this thread and add my comments accordingly.

Secondly - the foundations over an existing drain. This is covered by Part H of the Building Regs and you need to speak to your local Building Control Office to see what they recommend. The usual craic is a lintel bridge over existing sewers, but, as you say, it all depends on depth. Where a sewer/drain would run through a concrete footing, rocker joints can be used to isolate the section of encased pipework, but again, you need to ok all this with the BCO.

Forum Question Japanese Stone Drain - johneddy - 8 May 2002
I was recently introduced the the concept of drainage paving accomplished by laying thin stone vertically into bedding over a gravel drain. The pictures I saw were very attractive and while the concept seemed simple enough, I have been looking to be directed to a source of additional information or to those with experience in this area. Can you help? Thanks
forum answer Tony McCormack - 10 May 2002
I've only ever seen this used in gardens. John, as the labour element is quite high compared to throwing is a perforated land drain and backfilling the lot with a clean gravel.

To be honest, I've never seen a proper construction drawing for this type of drain, but we built one for a client in my village following the instructions from a book on garden design he had been reading. I can't recall the name of the book, but if I see him in the alehouse tonight, I'll ask if he still has it. All I can remember is that it was a 'coffee table' type book on building a Japanese Garden and featured many photos and descriptions, including the ever-popular 'deer-scarer' yoke for water features and a really elegant downspout arrangement for small roofs that consisted solely of a length of chain!

For the drain we built, we used stone roofing tiles bought from a salvage yard and filled the interstices with a 6mm local river gravel. The whole affair was about 450-500mm deep with a half-perforated clay pipe at the base which was then linked to the existing SW system of the property. If memory serves me right, we used 6 tiles, each around 30mm thick, and the overall width of the drain was about 250mm. It was used at the edge of a paved patio and was only about 4.5m in length.

As far as I know, it's still working. I'm sure that if there had been any problems with it, I'd have had my ear bent long before now!


12 May 2002

Thanks for rhe response. I would be most appreciative if you learn something from your your pub friend.
- john
Tony McCormack
14 May 2002
No sign of him last Friday, John. I'll see if he's in this Friday. I know he travels abroad on business quite often, so he might be away.
Forum Question Brick drive drainage - nowhere to go! - Richard Elliott - 13 May 2002
A challenge, I'm aiming to lay a brick drive, in order to stay 150mm below the dpc (not that it's really got one - it's a 450 yr old cottage, but I've assumed floor level) 1:80 gradient would mean the end at the road is below the pavement. Draining all or part towards the house and into gullies is a no-go as it hasn't a surface water drainage system, guttering discharges into flower beds or drive. Right hand side is no-go as it's a neighbour's property. Soak-away is a non-starter as it's heavy clay with the water table about 2' below the house (natural pond at the bottom of the garden is a good guide to the level. I gues the only option is a fall towards the left-hand side which is lawn and flower beds? the drive is approx 120 sq/mtrs is this feasable and would I use the same gradient across the drive (average width 5.5 mtrs)

Second part, I want to do it in a brick which looks old ie in keeping with a 450 yr old cottage and doesn't cost an arm an a leg, given the size - is reclaimed brick an option and if so what should I look out for, if not have you any suggestions?

Richard Elliott

forum answer Tony McCormack - 14 May 2002
I can't tell you what would be the best way to drain your planned driveway, as I',m not familiar with the property, but dumping 120m² of surface water onto a garden, plus whatever comes from the roof and other hard surfaces, is asking for trouble, especially with such a shallow water table.

I'd ask a professional for on-site advice. They might be able to spot a solution I can't see (obviously!)

As for choice of brick; why reclaimed? There is a very small market for reclaimed pavers and the quality ones are bloody expensive. All the rest are concrete or cheap clay seconds. Have a look at Tegula/Drivesett from Marshalls, Priory from RMC or Woburn from Charcon, to name but 3.

Forum Question Levels below DPC - Alan Malsher - 20 May 2002
I understand there is a "requirement" for paths, patios etc to be 150mm below DPC. Is this an ABSOLUTE requirement or just a wise precaution? What about steps out of a doorway; can these be at/near DPC level? What about an attached car port?

Is it essential to have a damp proof membrane under the car port (plan is to have a concrete base with paviors, car port open both ends)?

Thanks, alan

forum answer Tony McCormack - 20 May 2002
The 150mm below dpc rule is a very, very strong recommendation, but isn't a ruke for diy'ers working on their own property. Contractors are expected to work to this rule, and all new properties are built to this standard, and or good reason. It dramatically reduces the incidence of problems with damp.

For diy'ers, a problem may arise if they come to sell their property, as it's the sort of thing spotted by the buyers' surveyor, and you're faced with having remedial work done or reducing your asking price.

Steps from a doorway can be brought up to internal floor level (as in the relatively new Document M of the Building Regs) but a threshold drain or cavity of some form is required to 'isolate' the outside from the inside, or vice versa.

I'm not sure what you mean about the car port -a dpm beneath the car port? Do you mean a membrane laid beneath the planned paving? And does your 'concrete base with paviors' mean you're planning to use rigid paving?

Alan Malsher
21 May 2002
Yes, I am planning to use rigid paving. The proposed car port is immediately adjacent to the house wall with a fall of about 1:40 both along and away from the wall.
I plan the paving to be a sub base of hardcore - mainly broken brick, blinded with sand, then a DPM (if required) with 3-inch of concrete and paviors on top. The total slab is quite large (approx 6m x 8m) so am wondering how to accomodate expansion. Should I use reinforcing steel?
Thanks again.
Tony McCormack
21 May 2002
Why rigid paving? It's far more labour intensive than flexible, as well as costlier, not just for the special rigid paving bricks, but for the concrete, the mortar and all the other bits and pieces!

If I was going to all the trouble of using rigid paving, I wouldn't skimp by using broken brick as a sub-base - I'd play safe and use a 'proper' sub-base material, preferably DTp1, and you definitely need a dpm - all concrete slabs should have one.

At 8x6m, I'd say you ought to use reinforcing mesh, a simple 6 or 7mm mesh would be sufficient, but a 75mm thick slab doesn't provide adequate cover - you need at least 100mm thick to give the minimum required 50mm cover all round. You could consider using fibres instead, if you stick with a 75mm thick slab.

I'd split the area into two slabs, each 4x6m, with a movement joint between the two. You definitely need an expansion joint where the slab abuts the house wall.

I can't help feeling you're making this job far more complicated than it need be. Why do you feel you need rigid paving?

Alan Malsher
22 May 2002
You're likely to help me save money!
I'm reconsidering the whole idea of rigid versus flexible.
I'm going to get a couple of quotes.

I'm so glad this website has prevented me from going into this blind!

Tony, thanks.

Tony McCormack
22 May 2002
Let me know what you decide to do, Alan. smiley
9 Jul 2002
This thread was of interest to me also. I am just about to build new steps from patio to underside of existing door threshold. What form should the 'isolate' be? Would a strip of dpc sandwiched vertically between the new step and the existing house wall be sufficient? You assistance would be appreciated.

Thanks, David H

Tony McCormack
9 Jul 2002
Yep that would be fine, David, or you could just leave a 12mm gap, depending on the exact construction. The purpose is to prevent a 'bridge' that would allow damp to work its way above the dpc.
Forum Question How to connect? - Dave B - 21 May 2002
First I'd like to say that this is a great site, well structured nicely laid out, informative and helpful. I wish more web-sites were so good.

I have a question that I could not find the answer to on the site but forgive me if I missed it and maybe just point me in the right direction.

I am considering laying some land drainage and seemingly only have the option of connecting it into a combined foul and surface water sewer.

Your site states that I must put in a vented trap but I cannot find reference on how to do this.

I may have the choice (assuming that both options are feasable) of connecting into either an existing inspection chamber or into a surface water drain. Can you say what would be best and what kind of connections/traps I should use for each option.

Thanks in advance.

forum answer Tony McCormack - 21 May 2002
For connection to a combined or foul sewer, you need a trap of some form. I can't trace the reference to a "vented trap" - which page is it on? The trap doesn't actually need venting except under very, very special circumstances.

A simple low-back P-trap would do the job - connect in with a 90 degree knuckle bend, then the P-trap and then the connection to the FW or Combined system. Can you follow that or do you need a sketch?

If you have the choice between connecting to a FW or a SW system, land drainage should always be connected to SW as first choice (assuming there is no ditch/stream etc). Connection to FW is a last resort.

Dave B
21 May 2002
My mistake Tony so apologies - it says via a trap not as I read it, a vented trap. I should read better!

The explaination sounds clear to me so no need for a diagram thanks.

Hope this is not too silly a question but I assume its OK to have the trap buried and inaccessable, or should I be providing access to it somehow?

Again thanks.

Tony McCormack
21 May 2002
Yes, you should bury the trap but accessibility is something that needs thinking about.

If you're connecting to a SW system (or FW/Combined) you should be able to rod up from some downstream point to the trap. Further, depending on how large an area is being drained by the land drain, a catch pit upstream of the trap may be worth considering, not only to reduce sediment in the sytem, but to provide access for maintenance both downstream to the trap point and back upstream along the drain field.

I wouldn't bother with a catchpit unless I was draining more than 100m² of silty or sediment-heavy ground or 200m² of clayey ground.

Dave B
22 May 2002
Thanks for the help Tony - I feel I can get this right now!
Tony McCormack
22 May 2002
Let us know how you get on. smiley
Forum Question Manhole under conservatory - Wilks - 24 May 2002
Firstly, many thanks for an excellent way to discuss these types of issues.

Now to the problem. I wish to build a conservatory (planning agreed) that will enclose a brick manhole with three connections of waste water and sewage. I wish to move the manhole out of the proposed conservatory area about 3-4 feet. From this site I have an excellent idea how to do it, just wanted to know if anyone had similar work undertaken and how the council reacted etc. Luckily I am at the beginning of the drainage run so any interruptions will only affect me. The manhole is brick (house built 1929) and can easily be replaced by an inspection chamber,(2-3 ft deep), moving the existing feeds relatively easily. The nearest connecting manhole is that of my neighbour about 20 feet (6 metres) away. Moving the manhole will make this distance about 25 ft (8 metres). I have considered sealing the manhole where it stands, but keep deciding against it. Has anyone done something similar and what do you think best? I'm half inclined just to do it and not tell anyone...advice please..

forum answer Tony McCormack - 24 May 2002
From what you've told us, I can't see any problems with your proposal and there'd be no reason to do it 'secretly'.

Position your new IC where you want it away from the conservatory (at least 1m away, I'd suggest), then connect it up with the appropriate pipework, test it, then disconnect the old brick MH and pipework.

I'd dig out the old drainage and backfill rather than leave it in situ, but this may not be feasible. The old brick MH can be backfilled with a lean mix concrete and left as it is.

Forum Question Garden drainage - Peter Northall - 1 Jun 2002
Hi All, I recently posted this to the real gardeners forum, who suggested I should try posting here for expert advice, I hope you can help...

I recently moved into a new property in central London. It has a 30' x 30' (massive!) fully enclosed garden, which encourages me to follow in the footsteps of the rest of my family and get gardening.
The garden has previously been mostly paved and built on (temp wood structures), with very little given to plant or lawn. Grass which is evident is mostly moss, and winter evidence suggests drainage is a problem. This is also suspected because we are only 500 yds from the Thames (near Tower Bridge), so I would also expect v dense soil/clay.
I am removing most of the paving, then I will rotavate the whole area. I hope to raise a central circle (20' dia.)of the garden for the lawn.
I have heard speak of creating a 'Soak' below the lawn area, apparently putting a layer of rubble (of which I have plenty) and sand below the topsoil to aid drainage.
Is this right? What are the specifications (depths etc)? Are there any better alternatives?
Plus, as I'm starting this garden from scratch, any general purpose advice you could offer will be most welcome.
Thanks in anticipation.


forum answer Tony McCormack - 1 Jun 2002
Hi Peter,

read the page on Soakaways and the link to the FAQ I wrote for uk.rec.gardening on Improving Clay Soil. I'm sure they'll help you think up more questions, which you can post back here after you've read about the basics. smiley

Forum Question Approved Doc H vs. 150mm for DPC - Matt Taylor - 2 Jun 2002
am celebrating the golden jubilee by digging, and digging and...

Can I ask your advice on the drainage, etc?

I am a bit confused by my reading of Approved Doc H.

According to Diagram 10, in this doc, if I have 150 mm of cover (what do classes B, D, F and N mean? as well as bedding factors 1.1, 1.5 and 1.9?), then I am ok with my rigid pipes.

According to Table 8 though, it seems that I might need 600mm (looking at the fields column - is that what would apply here?).

Although, according to section 2.44, if I used the reinforced concrete slab, etc., I could get away with less.

However, where my foul drain from the toilet starts (and even for some length away from there), I only have about 150mm between the top of the drain pipe and where the top of the finished surface can be so that the finished surface will be no less than 150mm below the dpc.

Which one takes priority? the 150 mm below the dpc or the drain? I gather the drain, but it is still going to be tight, even following section 2.44 of approved doc. H.

How would you solve this problem?

Finally, I have one other question. Using a breaker near where the soil pipe enters the chamber, the seal around the bottom of the soil pipe cracked and a pece of the sealing material came loose (honestly, I was at least 1 ft or so away from it).

There is a gap of about 25-50mm between the bottom of the pipe and the top of the chamber, so when the piece came loose there was a gap.

I have temporarily cemented around this gap to seal it again, but what is the proper non-bodge way to fix this?

Thanks a lot and I hope you're enjoying this weekend more than I am (God, my muscles hurt!!),


forum answer Tony McCormack - 2 Jun 2002
Don't get too absorbed by DocH, Matt - it's used to ensure compliance of new build but for minor repairs or small additions to existing systems, it has to be treated as 'good advice' rather than 'strict law'.

The various bedding classes are more to do with soil mechanics and the various types of pipe material but the reasoning behind them would take a day to write out - take it from me that you really don't need to worry yourself about them. smile

If your pipewoirk is beneath a graden, path or patio, then surround it with 100-150mm of pipe-bedding and it should be fine. If it';s beneath a driveway or other trafficked area, then it ought to be concreted in, especially if it's uPVC. Clayware is much stiffer and can look after itself at shallow depths. If you plan to sell up, though, it;s worth iusing marker tape to warn any future occupants of the shallow nature of your new drainage.

Next - the damage to the chamber. If the mortar repair is holding, that will be fine. Under site conditions, we might use a granolithic mortar to repair, or, in some cases, an epoxy 2-part mortar, but for what little damage you seem to have done, a mortar repair should be fine, as long as you've packed in plenty of it into the gap and it's not just a Rizla-thickness skim.

Now - get back into that trench! wink

Matt Taylor
2 Jun 2002
Not back in the trench!!!

You have no idea how much I (and my very kind and helpful neighbour) ache!

But I had a real reason for writing besides just moaning. I wanted to clarify what to do where the drain pipe level is so high relative to the dpc.

I think I might have exaggerated a bit (unintentionally) when I wrote before. It's more like 120mm between the top of the pipe and the top of my proposed finished surface.

(I just stretched my legs. You wouldn't believe the technicolour bruise I have on my knee).

I'm the guy who wrote recently) in a different forum about using granite setts (50mm thick). That only leaves about 70mm below the bottom of the setts and the top of the drain pipe.

I'm thinking of a rigid construction (because that's what's used at the place that I saw them and really liked them).

According to your pages on rigid-construction setts, I can get by with just 50 mm of bedding between the bottom of the setts and the top of the sub-grade (clay down here in London -- very heavy clay, my back reminds me). I was going to have the usual 100mm of hardcore as a base in other places, but in this area where I only have 70mm between the bottom of the setts and the top of the pipe could I get away with 50mm of bedding with 20mm of the pipe bedding layer below that?

It is in a back corner of a patio that shouldn't (famous last words) get much traffic at all.

What would you do?

And one final question. There is tons and tons of concrete all around this chamber (for foul) and another gully for surface water, any ideas why? In some areas, it stretches for nearly 6 inches, perpendicular to the pipes themselves? I just don't understand.

thanks again,

P.S. Yes, I am taking pictures. My neighbour intends to use them to speed through the committment papers. But, if I survive this without hernias, insanity, etc., I'll pass them on to you (hopefully not just for the "don't EVER do it like this!!" pages). smiley

Tony McCormack
3 Jun 2002
Where the pipework is very close to the surface, I'd concrete in the pipework, leaving the top of the concrete at least (depth of setts + 30mm) below paving level. Then, lay a separation membrane over the concrete before placing the concrete bedding for the setts themselves.

This separation membrane could be a layer of 125 micron visqueen, if you have any available, or even old polythene rubble sacks, sand bags ftrom the BM or anything like that. The idea is to prevent the bedding material bonding directly to the pipe haunching so that, if, at some future date, the setts need to be lifted for whatever reason, they are not directly 'stuck' to the pipework and can be removed without affecting the drainage system.

There's no need for a sub-base where the pipe haunching is close to the surface. It can be re-introduced where levels permit, but it's not essential in this one spot.

The very generous concrete around the existing may be for any of a hundred reasons - they may have had loads left over from another job; they may have needed to protect the pipework from heavy loads; there may have been a worry about settlement - who knows? If you try to work out what the groundworkers were thinking when they did every strange thing you come across, you'll end up going mad! wink

Looking forward to the pics.

Forum Question What does this drain do? - Matt Taylor - 4 Jun 2002
Hi Tony,
guess who again.

Thank goodness this is the last day of the weekend. Unfortunately, the excavation will not be done today (even though we will have filled a 15 cubic yard skip -- how this happened when there is only about 25 or so square metres and we're only going down 200-300mm, I'll never know).

Anyway, yesterday we came across a drain that looks as though it is just for surface water. Top of the gully intact and cemented shape beside it that has the form of the bottom of a downpipe off a gutter (or something like that).

Only two things:
(1) this whole thing was buried under about 100mm or so of cement
(2) we followed the pipe, a metal one, that leads out of it and it continues past where the sewage goes behind my house. The sewage runs behind the house parallel to the back wall about 1 metre or so into the garden away from the wall.

The pipe from this old gully, etc., runs perpendicular to that back wall (away from it) passes over the sewage pipe that I mentioned in the previous paragraph (not that I dug down as far as the sewage) and then continues away from the house for at least another metre after that.

At that point we stopped digging (too much other digging to do).

I'm assuming that it was a surface water drain that just drains into the soil somewhere. But which is no longer used (I figured all the concrete on top put an end to that).

Does that make sense?

With a metal pipe, any ideas of its age?

thanks again, not it's back to the final day (this week :( ) of digging and carrying and...

forum answer Tony McCormack - 4 Jun 2002
15 cu yd skip? I doubt it - most are 7 cu yd or 5m³ and you can only get approx 4.5m³ of excavated material into them. A skip wagon wouldn't be capable of lifting 15 cu yd of excavated clay/soil/concrete, and it certainly wouldn't be able to carry it on the roads. As a guide, an 8-wheeler wagon, carrying a full 20T load holds about 9m³

Anyway - the mystery pipe. It sounds like a Cast Iron feed pipe to a soakaway, probably constructed from bits and bats of leftovers, possibly by a previous homeowner, as CI is not a cheap option for drainage.

Is it still functional?


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