aj mccormack and son

Drainage - Page 05
The Brew Cabin


July 1st 2003 osahonegbesolomon|DRAINAGE||||1057031127|i wish to make a new connection to a an underground  gully with a trap, i was wondering if it is possible to change the old dual system to a combined system. ie can i simply remove the the trap and gully and connect the single stack? or can i connect the new soil stack to the gully by creating a junction? TonyMcC|DRAINAGE||yes|yes|1057053571|I think you've got things the wrong way round - dual systems are not 'old' - it's combined systems that are old, while dual systems are more modern.

Further, you [b]CANNOT[/b] ever connect a foul drain (such as a soil stack) to a surface water system. You risk polluting a local watercourse as well as endangering health. It is sometimes acceptable to connect surface water to a foul system, but never, ever, ever the other way around.

Your soil stack can only be connected to a foul drain and it is best done via its own connection rather than piggy-backing it onto another fitting. osahonegbesolomon|DRAINAGE||yes|yes|1057098982|THANKS!
i will connect to the foul drain then, will it be better to use a mini access chamber or a junction? the surface water drain has the existing bath/shower waste, sink & basin waste as well as the guttering from the roof emptying into it via a whopper.
i am reluctant to cross over the surface water drain on my way to the foul drain, what can i do to avoid this?
surface water from the roof drains into a gully which in-turn drains into thesame inspection chamber as the foul drain, is this how it should be?
sorry for the foolish questions, i have had contractors take advantage of my ignorance in the past so i really want to know what should be done. thanks for your patience.

TonyMcC|DRAINAGE||yes|yes|1057104729|A mini access chamber is easier to fit and will make maintenance and access to the system much simpler should owt go wrong at any time. It also offers you the opportunity to connect-up other lines of drainage at some point in the future.

You say that the SW already has sink, bath/shower and other FOUL water emptying into it via a "whopper" (is that a typo or did you really think they are called 'whoppers?) that's fitted to a surface water system. If this is correct, then you've got serious problems. The foul from sink/bath/shower etc should only be emptying into the FW system, and preferablly via closed fittings, although open [b]hoppers[/b] are ok for sink waste.

Crossing one pipe over another isn't a problem as long as one isn't resting directly on t'other.

And then, finally, we come to the nub - if SW from the roof is ending up in the same IC as the sink/bath/bog waste, then what you have is a combined system, that is, fould and surface in one. This is an old way of draining poperties that is no longer used, but is allowed to persist in those properties were it exists, as changing over to a dual system would be all but impossible. If you are 100% certain that what you have is a combined system, then emptying foul into any of the upstream fittings from the IC will be fine.

Does this now affect your thinking on your first question? You originbally thought you had a dual system, but now, it seems, it's actually a combined. Have you tried asking any of the neighbours to see if they know what type of system you have? Alternatively, your local council Building Control Office will be able to confirm which system you have. osahonegbesolomon|DRAINAGE|||yes|1057123891|i have contacted th coucil they do not have a map of my drains in their office, i am trying to get a council officer to visit. however what i did not mention but i guess you must have infered it from my last query is that apart from the surface water and sink and basin and bath waste emptying into the gully via the hopper and into the inspection chamber, there is a separate foul waste pipe from the toilets emptying separately into the same inspection chamber.
the reason i was considering connecting to the IC via the gully is that; this is more accessible as the material used previously is clayware an consequently was not covered in a concrete haunch; also the clay ware seems to have suffered a bit of damage in the past and so would probably need replacing anyway. my contractor wants to connect to this but i am concerned that the foul waste from the new toilets may emit smells from the gully. i thought that soil stacks were raised above the roof to save us the smell? TonyMcC|DRAINAGE||yes|yes|1057503300|Apols for the delayed response, but I've been on me travels for a couple of days.

If the toilet is emptying into the same IC as the rest of the drainage, then you definitely have a combined system, and you're right: if you connect surface water fittings to this system, there is a distinct possibility that less-than-pleasant smells could vent through the new fittings, which is why it is essential that you (or your contractor) uses only trapped fittings, as these will prevent any sewer gases (as they are known) escaping and offending the noses of you and your family.

Soil stacks do project up to and beyond roof level so that gases can be vented without making anyone feel ill. This allows the gas pressure within the sewer system to be balanced with that of the atmosphere at large. Trapped fittings rely on a U-bend of water to prevent  such gases venting through gullies and linear drains which are, obviously, at a much lower level that the soil stack. osahonegbesolomon|DRAINAGE||yes|yes|1057617064| i had the mind of replacing the trapped gully system with a soil stack that reached above the roof, into which all the fowl waste and the guttering from the roof will be connected. however since the gully is already a trapped one. your explanation seems to suggest that it will be okay to connect to it as it is by fitting a mini access chamber.  thanks

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Forum Question What kind of drain? - Concrete Chris - 30 Dec 2002
I am new to drainage and have a query. I have a spot of land that slopes down to 2 stables. One stable is lower than the other as the land also slopes to the side. Down the slope is a walkway surfaced with planings. To the left and right of the walkway is earth.

A yard infront of the stable doors is concrete. Looking at the stable doors to the left is a gulley which looks like it peters out and then drains onto a lane which is another yard below below where the stables are.

The problem I get is flooding in the lower stable. I believe water some down the planings, hits the concrete spills up and into the stable. Very little turns left into the gulley.

What crossed my mind was digging a drain across the walkway about a yard short of the concrete that leads into the slight gulley. But when I read all the pages in the drainage section I began to worry that I did not have an "official" soakaway and would just add to the water flooding down the lane.

I am stumped as I thought it would be relatively easy job.


forum answer Tony McCormack - 31 Dec 2002
Hi again, Chris,

I'm not sure quite what qualifies as an "official" soakaway. If it's on your land and it works, then there's no problem with officialdom.

However, if water is already welling up from the ground, this suggests the ground itself isn't suitable for a soakaway, or, at least, it isn't suitable in that particular spot.

The gully you mention - am I right in thinking that it drains onto land that isn't yours? If so, is there some agreement or consent for the gully to operate? Or does it actually drain onto a public highway, the lane you mention? It may be that your simplest option would be to intsall a cheap linear drain, the sort you can get from B&Q for a tenner per metre) as an interceptor at the edge of the concrete hardstanding, and connect that to the gully pipework, and allow gravity to do the rest.

Concrete Chris - 2 Jan 2003 Thanks Tony and Happy New Year

Well I sat in the stable during the deluge yesterday to suss out what was happening and it was an eye opener. The path I mentioned come from round a corner behind a barn (crucially uphill). Surprisingly it was acting like a water motorway and collecting water from all over the place, zooming round the corner, down the slope, hitting the concrete slabs and  then into the lower stable!

I dug the gulley a bit deeper to make sure its start was below the level of the path and sure enough it filled within minutes and gradually started to soak away.

So I think you are right - linear drain into the gully. Also I will add a single layer of bricks across the door of the stable to catch any rain on the concrete slab as is done on many of our other stables.

I'll let you know if it does the trick.

Thanks again

Forum Question Legal responsibility for surface water - Jim Brooks - Jan 1st 2003

I have recently installed a large area of paving in my garden. It is drained in two directions with soakaways where the edge of the paving meets the soil.

My neighbour is complaining that during very heavy rain surface water is draining into his garden. I believe he is purely suffering from the natural effect of heavy rain and is simply doing a Victor Meldrew.

What is the legal responsibility for water running off paving slabs?


forum answer Tony McCormack - Jan 1st 2003
It's a grey area, Jim. Your neighbour can argue that the paving is responsible for an excess of surface water being diverted onto his property, while you can counter that it is the heavier-than-normal rain that is the cause, and, in the meantime, the lawyers' wallets get fatter and fatter. Ideally, you are responsible for draining surface water from your own property and not allowing it to endanger or compromise any other property, but there are obvious limitations on this, as nature is no great respecter of the law and flood water will follow the law of gravity rather than the law of man.

We always work on the basis that no surface water should ever deliberately or knowingly be discharged onto a neighbouring property. I would strongly recommend that you attempt to find some amicable resolution and avoid getting shirty with each other. Maybe a better intercpetor drain is required, or perhaps a length of linear drain connected to a new soakaway. In these situations, the fact that you are attempting to find a resolution is often enough to dampen the fire in the neighbours' argument.

Jan 2nd 2003
I've a similar situation here. My village is notrious for flooding (4 times in 2000, for example), although as far as we can find out our house has never been flooded. The borough council has been improving drainage, ditch maintenance etc. One of the latest 'improvements' was the reprofiling of the pavement at the entrance to people's driveways. The stated intention was to prevent any water on the road from running into the properties.

On Monday we had the first heavy rainfall since these changes and the results are distasterous. Once the ground was saturated the excess water in our garden pooled up on our driveway as usual. However, our neighbours' runoffs were diverted by the domed pavement into my garden (being lower than his.) I think our garden was holding the excess water from 5 houses. Fortunately the rain stopped before the water built up to the level of the house but we were concerned on Monday night!

I believe that a linear drain installed where my driveway meets the pavement (being the lowest point of all) connecting to the main sewer would sort out the problem - but who would install this? Would the council have to do it, or is it the responsibility of the local water company? How can I get someone to take action before the next downpour results in our house being inundated.

Perhaps I should add that the house is a 16th century Grade II listed building and as such the borough council and I have a legal duty to ensure that the buliding is maintained properly - quiet obviously, increasing the flood risk for the place is not compatible with this responsibility.

Finally, I'd also like the council to undo their reprofiled pavement as I am unable to drive my car out without bottoming on the new dome.

Many thanks for any comments

Regards - Neil

Tony McCormack
Jan 2nd 2003
Hi Neil,

your idea of installing a linear drain at the threshold between your diveway and the public footpath has one fatal flaw - if the surface water system is already flooded and surcharging (technical term for "overflowing" ) where's your linear drain going to drain to?

It might work, if you can outfall the linear drain at some point lower than the floodwater level at the threshold, but, without surveying the site it's not possible for me to say for sure what would work and what wouldn't.

Anyway, if you were to go ahaead with this plan, then responsibility for installation depends on just where the linear drain is sited and to where it outfalls. If it's on your side of the boundary and it connects to the SW system on your property, then the onus is yours, but, if it's actually within the public footpath and/or connects to a sewer on public property, then it's the local council, and you can bet your bottom dollar that they will ummm and aaahhh for a good 12 months before anything happens. If anything happens at all!

For now, I would suggest you contact the highways dept at your local council and ask for a site meeting to review your concerns over the flooding, the re-profiling work and the potential damage to your vehicles using the crossing. They'll eventually send out a totally disinterested technician-cum-inspector and it will be up to you to badger them into coming up with a suitable remedial plan.

Don't hold your breath. I had a similar problem on a property I owned in Wigan and it took the council 5 years to do anything about the surface water that came in through our front door on a regular basis. My lads could have done the job in less than a day, but we weren't official contractors to BigWiggin Metro at the time, and so we had to endure the comedy of errors performed by their DLO that they managed to stretch out to 5 days!

And even then, it still bloody flooded!!

Jan 2nd 2003
Thanks for your info. If the surface water system was overflowing then I could accept, to some extent, the situation, but the water us not even making it as far as the drain due to the humps in the pavement. I don't want to bother you with too much detail but the surface drainage empties into a stream about 100 metres away. In the past the stream has been blocked due to lack of maintenance but since 2000 a proper preventative maintance regime has been introduced and the problem shouldn't recur.

On Monday, once the level of water in my garden had risen sufficiently I lifted a manhole in the garden and the water drained away quite happily.

Another thought occurred to me - once the water has run off my neighbours' gardens and onto the pavement, does the council have a responsibility to drain it, rather than rerouting it into my garden?

Regards - Neil

Jim Brooks
Jan 2nd 2003
Hi Tony

Thanks for the information. It looks like my problem with Victor Meldrew is minor compared with the deluge being suffered by Neil.

The rain we have had in the last few days has certainly got Victor excited. If he spends any more time knocking on my door I will have to charge him rent!

As a last attempt at demonstrating that I have done everything I can I have decided to put a drain from the soakaway to the rainwater drain that is about 10 feet away.

I guess this simply means digging a sloping trench from the soakaway to the rainwater drain and inserting a reasonably large diameter pipe that needs to be somehow tapped into the rainwater drain below ground level. Is this a good idea? Any thoughts would be appreciated.

Regards - Jim

Jan 3rd 2003
Well, I've written a firm letter to the highway manager but doubt I'll get much response, so I reckon I'll be following Jim's drain/soakaway arrangement, plus a new drive.

(I should probably move this to another board but...) if I take off the existing gravel, raise the level of my drive by about 150 mm at its lowest (but nothing at the top) with DTp1, then cover the lot with gravel, will it affect the drainage for the ground which seems good to me (I estimate there was about 12 cubic metres of standing water on saturated ground at 2.30 am - by 6.30am it had all gone)? I assume I'll have to raise the level of the beds too with a load of topsoil but I was planning to redo the front garden this year anyway.

Many thanks - Neil

Tony McCormack
Jan 3rd 2003
Neil wrote...

Once the water has run off my neighbours' gardens and onto the pavement, does the council have a responsibility to drain it, rather than rerouting it into my garden?

Yes - if water is draining from a public highway onto your property, the council has a legal obligation to rectify the situation. You should stress this in your letter to the Highways Dept.

Raising the level of the drive and the planter beds will not have any great effect on the groundeater situation. It might make your drive stand proud of any future inundation, but that can't be guaranteed. Given that the floodwaters drained away reasonably quickly, I think it might just work, but I don't think it will eliminate flood risk completely.

Next, to Jim, and your plan to construct an overflow from your soakaway...I'm still not sure how this would work. If the Rain Water Pick-up (RWP) that you intend to connect to is, in turn, connected to the soakaway, then nothing is being achieved. It can only work if the RWP is actually connected to a sewer.

And if it is connected to a sewer, then a better solution would be to route as much surface water to this RWP as possible. How feasible is that?

Jan 3rd 2003
Thanks Tony - I feel a project coming on. I'm not bothered about eliminating flood risk - just reducing it to an acceptable level. I'll post details of my work on other boards as I progress.

Thanks also to Jim for letting me hijack your thread.

Happy new year! - Neil

Jim Brooks
Jan 3rd 2003
Hi Tony

I have managed to expose a rainwater drain and this morning I have dug a 6 metre long by 40cm deep trench from the soakaway to the drain.

The master plan is to run a pipe from the soakaway to the drain so that on the rare occasions when the soakaway fills up and overflows the excess goes down the drain rather than in the direction of Victor Meldrew.

The soakaway is around 2 metres deep and 1.5 metres in diameter. It is filled with very coarse gravel. It is situated just off the edge of the paving and takes all the run off from that side of the garden. The water simply drains over the edge of the paving directly into the soakaway. I have also dug an overflow soakaway which is 3 cubic metres but if we get torrential rain the main soakaway and the overflow both fill up (clay soil).

Maybe I should have installed a gully but I would now have to start digging up the paving to drain the water directly into the drain.

I have learnt some interesting lessons with this exercise. Take advice first rather than last is the main one.

Is there anything wrong with my plan to run a pipe from the soakaway to the drain?

Thanks - Jim

Tony McCormack
Jan 14th 2003
No - it all sounds fine to me. smile
Forum Question Cables, ducts and bedding material - Martin Askey - Jan 14th 2003
My local geology is granite with clay soil in Culm grass. Most if not all utility companies seem to avoid using granulates for bedding material, regardless of the type of services installed. My understanding is that rigid or flexible pipes need stable bedding and the liquid-carrying pipes need granulates to avoid joints breaking. Also the use of granulates aids the avoidance of tree rooting ingress at joints, therby prevent blockages.

It has been observed even perforated drainage pipes are laid without granulate bedding material. Surely this is foolhardy and detracts from the objective?

forum answer Tony McCormack - Jan 14th 2003
The methodology used by the utility companies and their appointed contractors for laying their cables, pipes and ducts does not come under the remit of any of the standards used for drainage, such as Sewers for Adoption 4th ed. or B.Regs:PartH. In a nutshell, they are a law unto themselves.

I know some sectional pipes/ducts and the larger installations normally rely on a bedding layer, but small "service pipes" and armoured cables are just buried in whatever happens to be the local terrain. Responsibility for these services mostly lies with the utility companies themselves (the exception being where they enter private property), so any damage is down to them.

With perforated drainage pipes, some folk choose to lay them in "as-dug" material. It's not something we recommend, unless the as-dug material happens to be a gravel or similar material, but then, no-one inspects land drains, do they?   frown

Forum Question Flooding adjacent to house - Philip F - Feb 3rd 2003
My house is very old (it's G2 listed) and is a few feet from and lower than the road. When wet aqua-planes from lorries come from the road and gather in a small paved area (maybe 5 ft wide between the house and the road). This floods and then the water comes into the house. The 20 year flooding event has been every other year!! So I need to do something!

Talking with people I like the idea of a soakaway and sump pump. I'd need to move the water some 100ft to discharge it onto some common ground that drains well. The land is pretty flat around me.

My questions are:

  1. - I understand that according to building regs the soakaway cannot be less than 5m from the house. So how do I get the water from the flooded area (approx 5 ft x 15 ft) between road and house to that soakaway?
  2. -Then I need to pump out the water from the soakaway tank. I've read some excellent stuff about design. Given the outflow is to level common land, is it ok to dig a trench and have the outflow horizontal/level or does it need a fall if its going to be pumped?
  3. - Is this the right approach anyway - are there other ideas I should consider? Like silicon spray protecting the area so the displaced gallons cannot get in? But I dont want to create wall breathing/damp problems.

Thank you!

forum answer Tony McCormack - Feb 4th 2003
Hi Philip,

taking your Q's one at a time....

  1. - 5m is a recommendation, and a good one, but there can be exceptions. However, you can divert the surface water from the area of flooding to the proposed soakaway by means of pipework. Install a gully at the low point in the flooded area and pipe it up to the soakaway.
  2. - pumping from a soakaway (which would be more of a sump than a soakaway in this situation) can be uphill or flat. It matters not.   smile
  3. - I can't advise on the use of silicone weatherproofing to a listed building (or any other building!) unless I'm familiar with the site. You need advice from an on-site survey by a specialist water/weather-proofing company.

It sounds to me that you best bet is to install an interceptor drain of some form, maybe a linear drain, at the threshold of your property, that will catch any washback from the public highway, and then to install a gully or similar at the low point in the area where water currently hangs. Pipe this to a soakaway, sump or other outfall as befits the site. If you are planning to discharge onto public/common land, you probably need consent from your local authority. A call to the Tech Services Department should help clarify the matter.

Forum Question Building Over A Storm Drain - Mark H - Feb 11th 2003
Can anyone help with the following question?

I have a storm drain running along the side of my house that empties into the stream at the bottom of my garden. I want to extend my garage. Can I build over the storm drain? If not how close can I build to it?

forum answer Tony McCormack - Feb 11th 2003
Building over any sewer is less than ideal, but is allowed, provided that suitable protection for both the building and the sewer are included in the plan.

Your architect and/or the BCO for the building work should be able to advise you as to the best remedy for your particular situation. It may require you to re-pipe the sewer, moving it outside the building line, or you may be required to encase it in concrete and bridge it where it passes beneath walls, but, as I can't see the exact layout, it's not possible for me to say what would be most suitable.

Are you building/extending the garage yourself, or will you employ a builder?

Mark H
Feb 12th 2003
I would be definitely using a builder if I go ahead with the extension.
Tony McCormack
Jan 12th 2003
Then the builder will be able to work out the best solution. When you consider the amount of work that goes into building an extension, shifting a line of drainage by a couple of metres and possibly installing one or two access chambers is a relatively minor detail.

The main thing to bear in mind is that there is a simple solution. I've never seen a sewer yet that prevented an extension being built. Don't worry!   smile

Mark H
Feb 14th 2003

Although I think I missed a vital bit of information which is the diameter of the drain is about 18 to 20 inches , does this make a difference to your responses?


Tony McCormack
Feb 14th 2003
Just a bit!!!!

At that sort of size, this must be a public sewer, and so moving it is a much larger operation. It may actually be better to bridge it, which means big money, just depending on the position and orientation of the pipeline relevant to the proposed extension.

Basically, when a sewer is bridged, two padstones are constructed either side of the sewer at least 450mm from the pipework itself. Then, steel-reinforced concrete lintels or a specially cast beam on summat like Holorib steel decking is used to bridge the pipeline, so that no part is in direct contact with the pipework. The concrete foundation is then cast over the top of the bridge. The key point is that the pipeline is NOT carrying any of the load imposed by the new building, which would compromise the integrity of the pipe.

You need to get the BCO involved. They need to approve any plan your builder/designer/architect comes up with.

Good luck!

Forum Question Land drainage - Matthew Trounce - Jan 14th 2003
forum answer Tony McCormack - Jan 14th 2003

Jan 14th 2003
Tony McCormack
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Jan 14th 2003
Tony McCormack
Jan 14th 2003

Jan 14th 2003
Tony McCormack
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