aj mccormack and son

Drainage - Page 07
The Brew Cabin


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Forum Question Riding Arena Drainage - Toast Frenzy - Jun 17th 2003
I already have a riding arena 40m x 20m, with no drainage, was thinking about porous pipes. One down the middle (40m length) then from this, one every 5-10m to each side, all at a depth of 1M. Will this be of any use?

Been looking at the Drainage for Fields and Gardens pages. Would I need somewhere for the water to go? I live in the fFens and the riding surface stays wet, odd puddle, for around 1-2 days after heavy rain. Any help/advice would be great.

forum answer Tony McCormack - Jun 18th 2003
There's a few other threads on this subject, and I'd suggest you work your way through them to assimilate the various nuggets of advice.

As I mentioned in the other Horsey post today, there's a school of thought (ie, me and a membrane specialist) that a drainage composite would be a better construction than a permeable pipework system and/or a non-woven membrane system.

Whichever construction you choose, you will definitely need somewhere to outfall the collected water. Whether that's a main sewer, a soakaway or a ditch, depends on the site itself. As your arena is already in place, constructing using a drainage composite is impractical, so maybe a permeable pipe is your best option, but you still need somewhere to outfall.

Forum Question Bendy drains - Paul Roe - Jun 23rd 2003

the BCO told me that I can bend my PVC drains to save putting in an IC. Does it bend?

forum answer Tony McCormack - Jun 23rd 2003

Are you saying that the BCO told you that you can install a bend within your run of uPVC drainage and omit the IC, or do you mean that you're going to try to bend a length of uPVC pipe to fit the project?

I'm having difficulty understanding what you mean with so little information.

Paul Roe
Jun 23rd 2003
The BCO told that I did not need an IC as you can bend pvc pipe. I think he meant to bend it not put a bend in the run. This is about a 8 mtr run. I guess it will only bend at joints and as it's quite a bend I assume that I would have to put a joint in at about 2 mtr intervals so it will probably cost similar to a mini access chamber.
Tony McCormack
Jun 24th 2003
You can bend uPVC pipes, but not by much!

However, if the BCO will accept a bent pipe rather than an access chamber, then so be it. If we're only talking about a bend of a few degrees, then there woun't be a problem, but anything more than about 10-15 degrees would be better done with a true bend, with or without an access fitting.

Forum Question Pitch fibre drains - lifetime - Concrete Chris - Jun 27th 2003
We recently had a blockage in our foul water system. On investigating we found our sceptic tank was full and backing up. We emptied the tank and rodded the drain. But the blockage was still there.

Unfortunately this meant a call to the men at ClearDrains who also could not rod and had to pressure blast the blockage.

The ClearDrains guy then said that the blockage was probably caused by our pitch fibre pipes coming to the end of their life. He also said that the problem may come again next week or next year. He also mentioned he could put a camera down the pipe for a mere £300.

What I would love to know is do pitch fibre pipes have a definitive lifetime? (these have been down since 1968). If so should we get on and replace the whole lot or can we replace where we had the blockage? The blockage was close to the sceptic tank rather than close to the house. One means digging up a field - the other means digging up the mother-in-law's prize garden!

Thank you for the help as always


forum answer Tony McCormack - Jun 27th 2003
As far as I know, pitch fibre is no longer recognised as a suitable material for drainage pipes. All the old spec books are archived and I can't get at them just at the moment, but, from memory, I think pitch fibre was dropped from the list of suitable materials in the early 1970s

I can't say what the design life of a pitch fibre pipe would be, as none of the current Drainage Fun Books give data on pitch fibre, but 35 years is not much, in terms of drain pipes. I would have expected a lifespan of at least twice that, but then, there were many 'new materials' used in the first couple of decades after the war that subsequently turned out to be more trouble than they were worth, not least of which was asbestos!

300 quid for the CCTV is about the going rate (I know firms that will do it for a bit less) and would be a good way of identifying whether the problem really is a result of pipe failure, and, if so, just how extensive is the problem. Are we possibly needing to re-lay the entire system, or is it just one or two sections that are suspect? 300 quid to determine this is money well spent, as it's the cheapest method of assessment; far cheaper than digging a load of test holes and certainly less destructive!

I think I'd get a price from the CCTV bod to survey the entire system with the aim of determining the state of the system and the extent of necessary repairs, along with some indication of urgency. There comes a point with all systems where it's more cost effective to replace the entire system than to patch sections here and there, and then cross your fingers in the hope that the remaining sections will last another decade or more.

If the survey indicates a serious problem in one or more areas, then it's time to get an estimate to replace the system and see how horrendous a figure they can come up with. If driving a trench through your beloved Mother-in-law's garden is likely to be unbearably painful, then it may be possible to use one of the 'no-dig' technologies, such as pipe re-lining, or even remote tunnelling, to minimise the devastation. Obviously, there has to be some digging, to replace fittings, access chambers, etc, but it's not always necessary to excavate a huge trench smack through the middle of the lawn and rose beds.

Concrete Chris
Jul 1st 2003
Thanks Tony

One small question though. If I have a digger and 2 blockages are within a couple of metres of each other in the field then is the camera still the most effective? I guess I am asking whether it is a skilled job.

Thanks - Chris

Tony McCormack
Jul 1st 2003
I'm not sure what you're asking. If you have the digger and two adjacent blockages, then replacing the blocked sections with new pipe is the best solution, but to survey the entire system in order to determine the condition of the pipes and extent of any other problems, then a camera survey is still the best option.
Forum Question New connection - Osahonegbe Solomon - Jul 1st 2003
I wish to make a new connection to 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?
forum answer Tony McCormack - Jul 1st 2003
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 CANNOT 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.

Osahonegbe Solomon
Jul 1st 2003

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 and 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 the same 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.

Tony McCormack
Jul 2nd 2003
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 hoppers 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 originally 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.

Osahonegbe Solomon
Jul 2nd 2003
I have contacted the council and 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 inferred 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 and consequently was not covered in a concrete haunch; also the clayware 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?

Tony McCormack
Jul 6th 2003
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.

Osahonegbe Solomon
Jul 7th 2003
I had the mind of replacing the trapped gully system with a soil stack that reached above the roof, into which all the foul 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.


Forum Question Linear drains, dpc and dpm - Xoan Carlos - Jul 8th 2003
Dear Tony,

First of all, thanks for your brilliant website, I spent over three hours reading through it on a Friday night/Saturday morning!

I've got several questions regarding how defects in my new house should be amended, so I hope this won't use up my quota. Our supposedly 'prestige' builders have made the ground level on our road/pavement too high, meaning that the airbricks in our building are either below, or at, ground level. This means a small strip (about a foot) in front of our house cannot be landscaped, and instead, the builders are planning to install an accodrain or linear drain. Likewise, at the side of our end-terraced house, the block paving that was against our wall, but on the adjacent house's drive has been removed and replaced by a grating, which I am told will eventually have another acodrain under it. However, the grating on the adjacent house's drive clearly obstruct the air-bricks and dpc. Should this be the case? As I understand it, a grating should be one course below the dpc and not obstruct the airbricks. What should I look out for once the accodrain is installed at the front of our house?

Second, alongside our garage at the rear of our house, the block paving on our drive slopes upwards to the point at which it rises above the dpc by two courses (there are clear signs of damp).  I have been told that yet another accodrain will be fitted here, but given the height of the paving, this will presumably remain above the dpc. Would this conform with B.Regs? Should I just insist on the whole drive being re-paved instead of settling for another gastly heel-trap for my wife to fall in to, (well, her shoe at least — she's not that thin) or for me to drop my car keys in to?

Finally, the rear of my garage wall joins on to the end of my garden, which rises above the bottom of the garage wall by at least eight courses. Again, there are signs of damp inside the garage, and I have been told that this is because the dpm is not functioning properly. Our builders have said that they are going to dig up our garden, apply a new dpm and replace the soil (mostly rubble actually!) From what I have been told, the dpm they have used sounds more like a brush-on application rather than a solid substance that I have read about elsewhere. Is this possible? Given that the dpm did not work in the first place, would I be better off just insisting that they lower the level of my garden to reduce the amount of earth resting on our garage wall?

Any guidance regarding any of these issues would be very much appreciated.

Regards - Charlos

forum answer Tony McCormack - Jul 8th 2003
Using a linear drain up against the brickwork to accommodate high ground levels seems to be more acceptable to some BCOs than to others, and I'm struggling to determine whether there is a national consensus on what's acceptable and what's not, as the BCOs to whom I speak are giving me conflicting information.

When I first queried this practice, a BCO working for a neighbouring LA told me that he'd allow it in exceptional circumstances only, and that the top of the drain would never be allowed to be higher than the dpc, yet a BCO in Liverpool told me that he was happy enough with the practice if that's what the builder wanted to do. If there are any BCOs out there who'd like to add their two-penn'orth, I'd be glad to hear from them.

My understanding at the moment is that using a linear drain in this manner is just about acceptable as long as it doesn't bridge the dpc (ie - is not level with or higher than the dpc), However, blocking off an air-brick with a linear drain would not be acceptable, as I understand it.

On your second point, the paving should not bridge the dpc at all and the fact that your builder seems to view linear drains as a cure-all for correcting any drainage issue where good practice has been overlooked or side-stepped completely, is worrying.

Finally, the dpm on the rear garage wall. I'm not sure what form of dpm has been used, but a paint-on type is normally reliable, assuming it's been properly applied, but it may be that a vertical drainage composite would be a better solution in this situation, possibly "backed-up" with a bituminous or polymer-based tanking product for extra security.

As this is a new property, it will be checked over by the BCO and possibly the NHBC bod at some point, to ensure compliance with the Building Regs and to issue a habitation certificate. If you have any concerns, you should check with your local BCO for their ruling.

Forum Question Smell from waste pipe vent - Jim B - Jul 8th 2003
Following the installation of roof lights in my attic, I've noticed that the waste drain vent pipe is emitting not too pleasant odours if the wind is in the wrong direction!

Question - What to do?

Cutting external vent pipe in attic and use of an air admittance valve - a possibliity, but matter is complicated due to use of septic tank. I understand that this would be OK only if septic tank was seperately vented?

Extending exiting pipe to roof apex level - a tad unsightly and one I would want to avoid if possible.

Any other solutions/products I've missed?

Any ideas welcome

forum answer Tony McCormack - Jul 8th 2003
Is this an internal SVP? It could be diverted outside and elevated to a position where any odours are not likely to find their way back into the house.

An AAV is possible, but it depends on the system layout and can be more trouble than they are worth unless they're properly fitted.

Proper external venting away from any windows and at a sensible height is the favoured solution.

Jim B
Jul 9th 2003
SVP connects to WC drain and goes up internal wall through slates. Main trouble is that the side of the house that SVP is on is the one where the prevailing wind comes from. So problem mainly when slight breeze is blowing as opposed to the higher speed winds of Oct-Mar.

AAV could v well be problematical as you say. Not sure I actually want a vent on septic tank inlet drain in the garden.

Easiest solution may be to install 2nd SVP on windward side of house where we have another bathroom, positioning it away from windows at adequate height.

A relative suggested that it might be possible to vent a sink, which could cut down on odours. No idea if this idea is a goer??

Tony McCormack
Jul 9th 2003
How is the malodorous whiff finding its way into the house? Would elevating the height of the SVP help eliminate the problem or could a bit of swan-necking deliver the odours to a point further away from any windows?
Paul Roe
Jul 10th 2003
I have similar problem, but have agreed with BCO that I can swan neck it so that it goes up the inside of the roof space to the ridge and then put a ridge vent in.
Tony McCormack
Jul 10th 2003
That sounds like a sensible solution - would it be possible on your job, Jim?
Forum Question Flexible joints/couplings - Paul Roe - Jul 10th 2003
I am diverting a drain and I intend to join the new pvc to the old clay using a flexible connector, the big rubber things with jubilee clips. Do you know if these things are flexible enough to allow a slight change in direction as I divert away from the existing line of the drain?

Also, is it ok to put these connectors in the middle of a run, or should they always be next to an IC?

forum answer Tony McCormack - Jul 10th 2003
"The big rubber things with jubilee clips" are more correctly known as Band-Seal or Flex-seal couplings. Now you know what to ask for when you get to the Trade Counter.   smile

They will accommodate a small amount of skew, but not a lot. You might be able to get 5-8 degrees, but anything more than that is best done with a proper bend unit.

They can be used anywhere within the line of drainage - indeed, their original purpose was to facilitate in-line repairs or to add junctions in the middle of a line. Absolutely no need for them to be adjacent to an IC or MH.   smile

Forum Question Patio run-off causing erosion - schnell391 - Jul 10th 2003
I have installed a dry laid slate patio off our sunporch. There is a roughly 1 foot drop off at the far edge of the patio, and I am experiencing a great deal of erosion off the bedding layer when it rains. I am using edging strips around the patio, but they are obviously no good. I am aware that I have probably done something wrong in setting the patio out in the first place. What suggestions are there for someone of my 'limited' ability?
forum answer Tony McCormack - Jul 11th 2003
Edging strips - what are these? Are they just pieces of slate laid 'on end' or are they some form of pre-fabricated item that might be used to edge a lawn or similar?

The correct construction for this type of job would be to use a flag-on-edge type construction, or even a dwarf wall, to retain the 300mm (12" ) uplift and prevent any erosion of the bedding layer....

retainer, if you have a 300mm uplift that is basically just bedding, then you need to contain it in some way. This could be as simple as laying more slate over the exposed bedding, but laying it on a full mortar bed, so that nothing can escape, if you know what I mean, or it could require you to take up the outer courses of the paving and re-construct a shown in the image above.

If you can get me a photo of the problem, I should be able to suggest a suitable remedial strategy.

Jul 11th 2003
Edging strips are flexible plastic strips that are spiked down to prevent the slate from 'creeping'. You can then landscape over them with either sod or something else.

I will try to post a photograph within the next couple of days. thank you very much for the assistance so far.

Tony McCormack
Jul 14th 2003
I know the sort of thing you mean - they are popular in North America but have never really caught-on over here. They can be seen on the Alternative Edgings page.

I have reservations about just how suitable these 'strips' are for retaining paving. If it were a flat patio, then I wouldn't be too worried, but using them as a retainer for 300mm or so of uplifted paving seems a bit excessive to me.

Jul 21st 2003
Okay, I have finally taken some pictures of the patio problem I am having. I will send the images to the email address listed in this website's help page, but for now, here is the link to view my patio images:

As you will see, I am getting a certain amount of base layer run-off from under the edge of the flagstone patio I have laid. I would like to avoid using cement as a solution to this problem if possible. I am wondering if I can solve the problem by filling more soil into the bordering garden box, and/or installing some sort of edging stone.
Tony McCormack
Jul 22nd 2003
I've re-posted the most relevant photo for you....

run-off patio

...The best way to cure this problem would be to lift and relay the outermost course of paving (or even the 2 outermost courses) on a cement-bound bed. That means mixing a small quantity of cement (10%) with the sand bedding that you've used, so that it binds together the sand bedding and prevents it being washed out from beneath the paving.

However, you don't want to use cement, so that makes it more or a problem. If you used a vertical edging, as shown earlier in this thread, you'd need concrete to retain the edging, and I'm not sure whether your dislike of cement extends to the use of concrete well below ground level. If not, you could adapt the vertical edging shown in my sketch above, and lay it so that the top of the edging abutted the paving, rather than sat beneath it, if you know what I mean. (See below)

However, if you really, really, really want to use a cement-free option, then the best method I can think of would be to use a separation membrane that retains the bedding beneath the paving something like the right-hand option on this sketch....

edge options

....personally, the cement-bound bedding option would be my favourite. It's simple, it's cheap and it will work. The edging is a lot more work, but would solve the problem, whereas the membrane is a lot of work and uncertain results.
Forum Question Hanging water in IC - The Wheel - Jul 24th 2003
I have just installed a second soil pipe and used a spare outlet from the inspection chamber and laid a new run of pipe approx 6 metres. I have noticed at the inspection chamber end I have an adjustable bend fitted and there is a small amount of water sitting in the bottom of the adjustable joint. It appears the inspection chamber is not level, do you think this is likely to cause a problem?

I would say the standing water is approx 20mm deep other than that the drain seems to function ok.

I could straighten the chamber but this would mean digging it out which I would rather not do unless it is going to give me a problem.

Cheers - Dave

forum answer Tony McCormack - Jul 28th 2003
It's less than perfect, Dave. Would it be a massive job to correct the IC? If so, it's worth 'tweaking' it now, to get rid of the standing water.

If the drain had to be inspected by the BCO, standing water in an IC is enough for them to fail the assessment, but, as this is just you doing the DIY, you could leave it for now. As long as the IC is regularly flushed from one source or another, I don't think it's going to be a major problem, and I would lose any sleep over it.

The Wheel
Jul 28th 2003
The standing water is in two of the outlet pipes both of which lead to soil pipes in two separate bathrooms so will be regularly flushed as there are wc connected to both pipes, the standing water appears to be only in the adjustable joint section. I have had a good look at the IC and one of the outlet pipes runs to nextdoor's IC and I have only got approx half a metre to there fence, so I suppose the only way I could do this would be to raise the IC at the other end - the one with the two outlets to the soil pipes.

Not sure how much of the run of pipes I would have to dig up to correct this. I have not moved this so I guess it must have been fitted this way. I was worried in case the standing water would eventually start to seep through the seals on the adjustable joints or even somehow block the drain.

Sorry if this seems daft but this is the first time I have laid any drains and I don't want to give myself a problem later on

Cheers - Dave

Tony McCormack
Jul 29th 2003
The seals should be more than capable of withstanding a bit of water, Dave. I think you can put the cover back over this IC and stop worrying about it. I've seen far worse in older, brick-built chambers, and they still manage to function for decades!   smile
The Wheel
Jul 29th 2003
Thanks for the advice. It's good to know there is somewhere us diyers can come for advice

Excellent site - cheers

Forum Question Non-functioning soakaway - Alexben5 - Jul 42th 2003
We've had "flooding" from our drive (30ft x 30ft area) close to the house for the three years we've lived here every time it rains. Discovered that there was only soakaway drainage, so dug from down pipe until we found a collapsed, silted up, rubble filled soakaway approx 12ft from house. Emptied it and realised that it was surrounded by clay so dug..... and dug.... and dug, only to find..... you guessed it - more clay!

Local geological plans show - yes, clay! Deep! The existing hole is approx 4ft square x 4.5ft deep. Needed a pump to get rid of water whilst digging and hoped that we'd find the hole empty next day - 10 days later we think it might have stopped filling and we don't know whether we're looking at the water table or just saturation of the surrounding ground (water level is about 3ft below ground level. We've heard now from the neighbours that the surface water drainage has always been a problem to this property, so much so that they had to put up kerb stones to stop the flow from our property to theirs! Neighbour the other side had a similar problem so lay a deep gravel drive. Looks like this soakaway has never worked! No SW mains available to tap into.

Drive slopes down towards the house from the road and we're obviously keen to get a solution before the autumn, otherwise we're going to have to get some carp to put in this bloody hole.  Any suggestions?


forum answer Tony McCormack - Jul 28th 2003
Ghost Koi are supposed to be very attractive, but a couple of fairground goldfish are probably the most likely to survive in such conditions!  wink

Seriously. I think you're fighting a losing battle. I can't see a soakaway working on your site, even if you built a proper one (ie, not a rubble-filled hole), and, if you did manage to build a working soakaway, you'd soon find that all your neighbours were benefitting from it, rather than you, as you're at the bottom of the slope and so "last in line", if you know what I mean.

Are there any drainage points at all that could be used, even if they are Foul Water?

Forum Question Drainage for gravel drive - Rachel Benson - Jul 24th 2003
Am I correct in thinking that drainage for gravel drives needs to be the perforated clay pipes laid within the gravel?

We have a problem with dampness penetrating through porous brickwork below the DPC which is related to drainage problems with our present drive construction. We intend to dig out the old concrete - it is at present only one brick below DPC, should we take it to 2? Then we intend to put a membrane against the outside house wall, lay appropriate drainage pipes to intercept ground/surface water and then fill with gravel. Does this sound like a good plan?

We intend to call in contractors, do we look for drainage /civil engineers or will the normal drive contractors be able to help us with the drainage too?

Really think you ought to be on some sort of commission for this site!! It's brilliant!


Oh yes, are we allowed to connect the surface water up to the foul drains, the house is old with extensions, the old bits have a combined system and the new bits seem to run freely when hosed for some time, but we have no clue where they go?

forum answer Tony McCormack - Jul 28th 2003
Rachel writted...

Am I correct in thinking that drainage for gravel drives needs to be the perforated clay pipes laid within the gravel.[

Not nesser celery. If a sub-surface drain is required at all, it can be plasticware, but clayware is better at shallow depths. However, unless there is a big problem with groundwater, sub-surface drainage should not be necessary and a normal surface drainage system of some sort should be appropriate.

We intend to dig out the old concrete,it is at present only one brick below DPC, should we take it to 2?

Yes - I would. If you're going to all that trouble, you might as well do it right!

Does this sound like a good plan?

I'm not sure - without the benefit of seeing the site for meself, I can't really say what is best, but, from the linmited information I have, what you're proposing sounds feasible.

Will the normal drive contractors be able to help us?

A good driveway contractor should be able to cope with this job. In fact, listening to their preferred remedial options would be a good way of sorting the wheat from the chaff.

Really think you ought to be on some sort of commission for this site!!

I agree wholeheartedly! Some kind users, such as the inestimable George Galley Rat, have made donations to the "Keep Tony Properly Hydrated Campaign" in the form of cases of Boddingtons left at my local Offy, but fine Pork Pies, Jameson Whiskey or holidays in sunny climes are also welcome.  smile

Are we allowed to connect the surface water up to the foul drains?

Only if there's absolutely no other option and as long as you use a trapped connection.

Is that it? smile

Rachel Benson
Jul 28th 2003
Brilliant - Thanks very much!
Forum Question Drainage into neighbour's garage - Edeve - Jul 26th 2003
I have had a patio put in by a local guy who was recommended by a friend. Some months after completion my neighbour noticed his garage was waterlogged- puddles against half the length of the wall.

The area affected can be best described as.....

  1. Widening of existing path between my house and his garage
  2. His garage is single skin brick
  3. The paving runs up to his garage wall in places
  4. Where the paving doesn't run up to the wall I have put down stone chips to make up the last 30-40mm level.
  5. The level is up to 150 mm above the neighbours dpc for most of the wall with a concrete ramp that is up to 190mm above at its top there is a drain on one end of the garage where some water will fall away and a run beneath the patio into it.
  6. The contractor assured me that putting a membrane against the wall and running the water away from this wall with the slab levels would prevent any problems- well thats not been the case.

I've had the contractor back- who has since retired and closed down his business for health reasons. Bad back- not uncommon in his line of work I believe. He says obviously he can't do the work but advised that there must be a break in the dpc membrane he put down and that digging out the areas and patching/ replacing this would be simple and sufficient.

My neighbour is a good guy and is being pretty patient so far. I don't want to depend on his good nature for too much longer.

I am not convinced by my contractors advice and would like some other advice- will his recommendation work.

forum answer Tony McCormack - Jul 28th 2003
What type of Damp Proof Membrane was used? From what you say, it sounds as though it was a polythene sheet (Visqueen PIFA 1200 or similar) when a proper asphalt tanking or drainage composite should have been used.

To be honest, I don't think a rip in the DPM is the problem - the whole thing is wrong. The paving should not be higher than the neighbpour's dpc and it is this that is the cause of the problem.

There are a couple of repair options - either a proper tanked membrane is applied to your neighbour's wall (with their permission, of course) or the level of the paving is reduced to below the dpc. Any other strategy is a "sticking plaster" approach, as far as I can see.

Jul 28th 2003
Thanks Tony,

It looked to be a polythene sheet, blue if that means something to you.

Forgive my ignorance- what do you mean by tanking? and how would it typically be fixed in place?

This is an awkward side area of the house. Reducing the level of the whole area isn't really practical- it would have to be a drainage channel as you have shown elsewhere on your site. A trip hazard for my daughter. Would it need to be 200 mm in width as you show on one of your pages?

Is this the building regs standard? Would 100mm be sufficient?

Sorry to bombard you with questions I want to get this right second time and not third!

If the drainage channel is is the more robust/ dependable of the two options then I would prefer to do this.

Thanks again for your help,


Tony McCormack
Jul 29th 2003
Blue polythene is usually a Visqueen membrane. This is an adequate DPM beneath concrete, but not for vertical applications, such as against a wall, which brings us to tanking.

Tanking is a coating of asphalt applied to a wall or other structure to render it completely waterproof. It's normally applied in 2 or 3 stages - I'm not sure as it's a long, long time since I last did it - gradually building up the thickness of the bitumen/asphalt. Tanking is most commonly used with relatively deep underground structures, such as cellar and basements. There are also bitumen-based coatings than can be used in situations where the pressure from groundwater is not likely to be too severe, and I would hazard a guess that your scenario would fall into this category. The tanking medium, whichever is used, is painted onto the wall and brought to a base, thereby shedding water away from the structure. Your local BM will be able to tell you which products they have available, and how they are best applied.

If you decide to go with a dry channel arrangement, the channell need be only 100mm wide, if that's better suited to your property. Such an arrangement is not covered by building regs, as the existence of the dry channel of any width is deemed to be compliant, and so there is no specific ruling on what the minimum width should be, but most BCOs would accept a 100mm wide channel in awkward situations, such as you describe.

Forum Question Drains far too shallow - Hillheader - Jul 29th 2003
I have excavated an area of crazy paving outside our front door (around 100m²). I encountered (and broke) a clay drain taking surface water from the drive. Unfortunately I also discovered that the drain then goes through the house granite wall (underground) and then lies unprotected under the lounge floor (suspended floor 2ft above bare earth). The drain then exits the other side of the house  and eventually into a soakaway. All this is rather bizarre, but the real problem I have is that it is a huge amount of work to lower the level of the drain (I would have to dig up the lounge!) or re-route the drain round the house (requiring a 15ft deep trench due to levels). What would be the best way to protect a new drain that would be only 8" below the level of a new block paving area, given that this area only gets pedestrian access?
forum answer Tony McCormack - Jul 29th 2003
Haunch it in concrete. At such a shallow depth, and for surface water, I'd weigh up whether it could be completely replaced with a linear drain, and so avoid all the hassle and expense of laying pipework on convcrete, haunching it all, providing flexi-joints every few metres and getting the falls right.

Would that be a possibility on your job?

Forum Question A small soakaway and a damp cellar - Simon S - Aug 15th 2003
I've a couple of problems that could use some advice...

Firstly I need to build a soakaway for the guttering of a small porch. This currently discharges onto stone flags at the base of the porch, which is unsatisfactory according to a survey that was carried out on the house prior to purchase. As the volume of water is small, how would you recommend such a soakaway is constructed?

Secondly I have a reasonable amount of standing water in my cellar. It never really amounts to more than a puddle, but is irritating as it restricts the use of the cellar, and also carries up mud through the stone flags from the ground below. Upon lifting a flag I found another layer of flags, and under those a brick floor, which leads to me to believe that the floor has been raised in the past to alleviate this problem (the house was built around 1870). In the opposite corner of the cellar (which is dry!) is a small drain, which seems to function.

What would your recommendations be to resolve this problem?

Many thanks in anticipation.

forum answer Danensis - Aug 18th 2003
In my experience many houses with cellars are built with a stone drain adjacent to the walls. This is constructed by placing strips of thin stone vertically a few inches from the cellar wall, and then laying the flags on top of these, to leave a narrow channel. Sometimes these drains also have a stone base. The stone drain leads to one corner where there is a channel to the outside, and a soakaway (or in one house, a way through to the neighbour's cellar, which was lower!). Over the years these drains become blocked with silt, or the soakaway clogs up. You can sort the first problem by rising them out with a hosepipe, but if the soakaway is blocked you have a problem. I have the suspicion that you can use a flocculant to clear them, but I'm not an expert on this side of things.

Our house is built on a couple of springs, and we have running water in the cellar, but by channeling it to the edges and applying a little heat and adequate ventilation we have made it reasonably habitable. In my last house we cured a very damp cellar using a small radiator and plenty of ventilation, though it did take a year to get it dry.

The worst thing you can do is to waterproof the floor, as this just forces the water up the walls, and you then have an even bigger problem.

Tony McCormack
Aug 14th 2003
Apols for the short reply, but I have to go in 5 mins

Soakway - same construction as given on the Soakaways page - note that a hole filled with broken bricks and old flags is not a soakaway: it's just a hole filled with broken bricks and flags!

Cellar flooding - a submersible pump, either one with a float switch or one you switch on as and when you need to.


Simon S
Aug 18th 2003
Thanks for the replies, I'll definately think about channeling the water to the drain, that sounds like a good possibility.

Best wishes

Forum Question Fall on linear drain - Stoat Gobbler - Aug 15th 2003
I have a long driveway that slopes toward the house from the road. At the bottom of the drive (which is of tarmac construction) is a concrete section in front of my garage. This concrete section(under a car port) has a drain in the middle of it which I now realise runs into a soak away which is obviously blocked because the area floods and pours into my garage.

I want to lay an Aco linear channel along the front of the concrete section, where it meets the tarmac. This would be approx 5metres in length but is unfortunately level with no drop to where I want the outlet. What sort of drop do I need for this length of drain? To do this would leave a step along the length. I would rather use a channel with a built in drop but these are three times the price of the level ones.

Can anyone help with suggestions of what I should use and how to overcome this problem?

forum answer Tony McCormack - Aug 18th 2003
For a 5 metre length, you can lay the Linear Drain (Aco is a brand name) with no fall at all - as long as there is an outlet connceted to a suitable disposal point, water will find its own way out of such a comparatively short length of channel.   smile
Stoat Gobbler
Aug 18th 2003
Thanks. That makes life easier and much less expensive!!!!
Forum Question Blocked soakaway - Stoat Gobbler - Aug 15th 2003
I have a soakaway that is located approx 4 mtrs from my house and underneath a tarmac drive. It is blocked and the the water does not drain properly. Is there any way of clearing it other than digging up the drive to locate it?
forum answer Tony McCormack - Aug 18th 2003
The short answer is "No" - if it's the pipework that's blocked, then you stand a chance using rods, but, if it's the soakaway itself, then it's time to start again.
Stoat Gobbler
Aug 18th 2003
Thanks, I thought that would be the answer!

Is the soakaway to close to the house anyway? And what is an average depth for them?

regards - will

Tony McCormack
Aug 18th 2003
Yes - too close (10m is recommended, 5m minimum)

"Average depth" - no such thing. Depends on site, and are being drained. See soakaways page.   smile

Forum Question Blocked french drain - Mark AT - Aug 19th 2003
Last year I added some french drain to my rear garden to supplement existing drainage. The latter supported drainage from an active spring(!) and two open covers to allow excess surface water to flow. Our field backs onto open fields which run off into our garden. This flows through 100mm pipe into a ditch 60yds away. There is also a 12' land drain at the rear of the fields. The ground is clay.

I added some additional french drain in the garden to stop it getting totally sodden in winter/spring. This was piped into the existing land drain in the garden. One drained from a flat area of garden which was sodden due to the aforementioned spring. It works perfectly and works very well. The other ran from from the top of the garden (being joined part-way by another)  and fed into the original pipe from the spring: i.e. the one that should carry the bulk of the water. This latter pipe has become clogged. Although it joins the 1st pipe later on.

Even in this weather the spring flows well! The blockage has caused the water to backup and then seeps out of the drainage pipe and through the ground.

I dug an exploratory hole to see what was going on and the pipe is full of water but without any sediment in the area where I inspected. I wanted to rod it through but was concerned that any blockage may block further down the pipe resulting in a far bigger problem!

During the winter the run off from the fields was bad and resulted in the garden being flooded (2" rise in 3 mins). To ease the problem I opened up part of the drain to allow run-off to flow into it. This is into the area that is now causing problems.

I don't understand why this problem should have shown itself now, given the current heat. Any ideas?

Is rodding/flushing likely to cause bigger problems?

Is it likely that gravel has clogged one of the junctions and then caused an increase of silt build up?

Any ideas /thoughts would be very gratefully received as a boggy lawn is not welcome - even in this heat!


forum answer Danensis - Aug 19th 2003
If you rod from the downhill end (which is the right way to rod anyway) you shouldn't cause any problems, though you may get wet.
Tony McCormack
Aug 30th 2003
I agree - rodding is the first strategy to try. It may be summat dead simple like a collapsed joint, or (and don't laugh!) a dead rat that has not decomposed fully.

Use rods to determine just where the blockage occurs, and, if the rods don't shift it, dig down there to find out why.

Mark AT
Sep 1st 2003
I had to dig to do the rodding (the builder never left a rodding point!).

The drain was blocked with roots and silt (we have clay soil). Should vegetation like this really be there to cause problem?

Tony McCormack
Sep 1st 2003
No, but, if the eejit builder wasn't bright enough to include a rodding eye or other access point, it's unlikely that the drain was enveloped in a root/silt membrane, as is shown on the Land Drainage pages of this website. That's more'n likely the root cause of the problem (ha ha!)
Forum Question Shallow pipes - Barry Moor - Aug 31st 2003
I have just discovered a 6" clay sewer - 11" below what will be the finished level of a block paved drive. What should I do to prevent damage to this pipe by type one aggregate or vibrating plate?
forum answer Tony McCormack - Sep 1st 2003
Encase it in concrete, with flexcell joints at the couplings. There's a drawing on the Laying Drainage page which illustrates the idea.

Alternatively, you can lay a 450mm wide strip of 50/65mm thick pcc flag over the top of the pipe, ensuring there is at least 50mm of sand cover between the top of the pipe and the base of the concrete flag. This is adequate for a typical residential driveway where there'll not be owt heavier than a 4x4 travelling at low speed.

Forum Question Drain connection - Hally - Sep 14th 2003
Hi, I'm currently in the process of installing some new pipework, downpipes from new garage and drainage from new retaining wall both to join into new 110mm pipework

My main problem now is how to connect into an old (still connected ) clay drain pipe. On a combined system I beleive this must be a trapped connection - would a bottle gully be the answer I'm looking for?

o/d of clay drain is approx 130mm

forum answer Tony McCormack - Sep 8th 2003
A trapped connection must be used when connecting surface water pipes to a foul or a combined system. This can be done by means of a single trap where the SW system links to the Combined System, or by using trapped gullies at all pick-up points. If your proposed Bottle Gullies incorporate a trap, then they will be fine.

Linking new pipework, whether it's clayware or uPVC, to older, salt-glazed pipes requires an adaptor coupling, which you should be able to get from any decent Builders' Merchant.

Sep 8th 2003
Hi Tony,

thanks for your reply. I'm now going for a P-trap at the SW-combined system connection point with new rodding point on the SW side. I'll then be able to rod to both sides of the P-trap unless you see any problem with that?

Congratulations on a great website

Tony McCormack
Sep 9th 2003
Sounds fine to me.   smile
Forum Question Plastic field drain pipe - Kim Feickert - Sep 8th 2003
I need advice concerning the laying of plastic field drain pipe, to remove water running downhill toward the house.

We have excavated for a garage etc and have created falls to take the water away from our cottage, but still need to redirect surface water off a bank before it gets to the "levelled site"

I'm planning on digging a trench along the base of the contour and putting in plastic drain coil, with a 800mm (approx) granite drystone dyke, outside the line of the trench.

The drain will have constant fall and I hope to be able to pipe it into a collecter or sump of some sort, from there pipe it in solid plastic to another sump, which will be taking another drain and then away across a road to a burn.

When I put the drain coil in, do you have to line the trench with anything or can you just put the pipe on granite chip and backfill with the same? I have heard that sometimes a plastic is used, is this correct?

The run of pipe is about 40m so is 100mm pipe ok?

I was hoping to link the two sumps with 100mm solid plastic pipe, and maybe 150mm for the road crossing?

Does this make sense?

Any advice would be appreciated.

forum answer Tony McCormack - Sep 8th 2003
Have you read the pages dealing with Land Drain Construction? This shows standard construction cross-sections, including the use of a permeable geo-membrane which is now a recommended practice.

The diameter of pipework to use is determined by the size of teh area being drained. Generally speaking, 100mm diameter is adequate for most residential purposes. 150mm for the solid pipe should be more that adequate.


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