aj mccormack and son

Drainage - Page 01
The Brew Cabin


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Forum Question Land drainage - Matthew Trounce - Jan 11th 2001
We have an extremely waterlogged 1/3 acre garden in a rural part of North Somerset. Drainage for the house and garden is wholly inadequate and is serviced solely by a small but flowing ditch alongside the 100 year old property that flows into the IDB rhine system.

We are only 7 metres above sea level, 1 mile from the coast and due to the current weather conditions the water table is approximately 300mm under the lawn (an improvement on November's position of 300mm above the lawn!)

We have concluded that we need to land drain the garden into a concrete sump and then, due to the levels, mechanically pump out to the dich and away.

Is there an ideal level below the surface to set the drainage pipes to give maximum effect and minimum pumping and is there an optimum size of sump?

Clearly the water table will drop in the summer but I suspect that the pump will be pretty busy through the winter months. Is there any advantage in using the sump capacity or will it just silt up in not fully pumped out?

forum answer Tony McCormack - Jan 11th 2001
The trouble with building a sump at such a low-lying location is that you could end up pumping forever and a day and getting nowhere. The most obvious outfall is to the ditch, but if that is tidal, or just not coping with current conditions, then that could turn out to be a waste of time.

For gardens, it's usually recommended that pipes have at least 450mm of cover. As for size of sump, that will depend on just how effectively it can be pumped clear. The trouble is that, as you drain your garden and store it in the sump, the groundwater in the surrounding land will most likely drain into your garden along the hydrostatic gradient created by the sump, and so, theoretically, you're draining not just your patch of one-third acre, but all the adjacent land, which could be 2, 3 maybe even 5 acres.

You really need to bring in a local drainage consultant to survey the site and advise you accordingly. I can't suggest any guaranteed solution without being familiar with the site, and Somerset is a bit off my patch, unless you can wait for the summer, when we usually have a week-long break with friends in North Devon.

Forum Question Waterlogged garden - Kate Paterson - Feb 5th 2001
We have recently moved into a house in Odiham, built in 1988, that seems to have a very waterlogged clay garden. The garden is at present totally undeveloped so we have great plans for it, including a patio. It is a mid-terraced house, and water from the roof is drained via pipes at the back of the house underground. All the water inside the house drains to the front of the house.The garden slopes towards the house,and we are puzzled by a drain cover at the higher end of the garden (away from the house). Does anyone have a clue what this might be? How do we find out whether the water from the roof is draining into this? Who do I approach to advise me locally regarding necessary drainage for the garden without leaving it dry and hard in the summer? Is this something I am likely to be able to figure out myself (with no experience, but lots of enthusiasm!)Please save me from the mud and reply!
forum answer Tony McCormack - Feb 7th 2001
Kate said......

we are puzzled by a drain cover at the higher end of the garden (away from the house). Does anyone have a clue what this might be?

If you are part of an estate, it could be an access chamber to the main drainage system. On such a modern property, your local authority will have drainage plans on record at their offices.

How do we find out whether the water from the roof is draining into this?

Easy! Have you got any childrens' poster paint? Fill ahousehold or mop bucket with water and add a generous dollop of the paint to the water, sufficient to distictively colour it. Then, while a friend or partner keeps their eye on the channel in the mystery inspection chamber (IC), you can empty the coloured water into one of the gullies or pick-up points that takes water from the roof. If the coloured water appears in the IC, then you know the two are connected.

You can also buy special drain tracing dye from builders' merchants that do the same thing.

Who do I approach to advise me locally regarding necessary drainage for the garden without leaving it dry and hard in the summer? Is this something I am likely to be able to figure out myself.

A local builder or drainage contractor is your best bet, Kate. There's some basic guidance to installing land drainage on this site, and there's a faq I wrote for uk.rec.gardening entitled Improving Clay Soil HERE which you may find useful.
Forum Question Lawn Drainage - Sian Baron - Mar 9th 2001
I have got dreadful problems with surface water in my garden. The soil is clay and the garden slopes towards the house. whether it rains for a couple of hours or a couple of days makes no difference, the water lies on top of the grass in large pools, and runs onto the patio completely submerging it.

I have had several builders and landscape gardeners opinions ranging from rotavating sand into the soil to laying perforated clay pipes to using Teramm(?).

Every opinion has conflicted with the next and I am now at a complete loss as to what course of action would be appropriate. Can you make any suggestions or give your opinion on the advice I have already had?

forum answer Tony McCormack - Mar 9th 2001
I doubt that incorporating sand into the soil will, on its own, alleviate your waterlooging problem, but used in conjunction with a land drain system, it could be of benefit, in that it will improve the soil structure.

The perforated pipe is probably the best solution, but you need to have somewhere to where these pipes can outfall, such as a sewer system, preferably a surface water system, or a ditch, stream etc. I doubt that a soakaway is going to be feasible given the conditions you report.

Terram is a brand name for a range of geo-membranes and drainage composites. The primary use for the Terram geo-membrane in the land-drainage business is to line land-drain trenches in order to prevent infiltration of small particles of silt, clay, etc. that can clog the system. The drainage composites are used for fin-drains and are being used successfully on commercial drainage schemes, but I've never used them on a residential scheme; I suspect the price would be prohibitive.

In your situation, I would look at using an 80mm dia perforated flexible plastic pipe, as described in the land drainage section of this site. It's cheap, simple to install, and highly effective.

Forum Question Flexible Perforated Pipe Conundrum - Tony Dobbyn - Mar 24th 2001
Well done on the site. It is refreshing to see a fine, easily read, yet comprehensive site.

And so to the conundrum.

If Flexible Perforated Pipe has holes all over but particularly in it's lower surface how does it 'carry' the water away? Surely the water simply flows in through some of the holes and out through the lower holes and so cannot be any more effective at land drainage than a sponge or a wet towel.

I have tried the hose test and not been impressed. Is there more to this piping than meets the eye?

forum answer Tony McCormack - Mar 27th 2001
The perforated pipe works by providing a conduit along which groundwater can flow. Imagine that the surrounding soil/backfill/pipe-bedding is saturated, that is, it is so chock-full with water that there is an actual pressure generated - this is known as hydrostatic pressure.

Now, if you introduce a pipe that has a big empty space in the middle of it, the water will flow into that space, thereby reducing the hydrostatic pressure in the surrounding material. It doesn't escape out of the pipe through the perforations because the hydrostatic pressure on the outside is still greater than that within the pipe, and so any water acquired by the pipe will flow, under gravity, along the pipe to some point of outfall.

It's all simple physics, really. smiley

Forum Question Water runoff from hillside - Grant Muckart - Apr 23rd 2001
Hi Tony,

My query concerns the water that drains off the hillside behind my brother's house and ends up saturating the garden soil in a long flower bed that runs the length of his back yard. His house sits at the bottom of a hillside in a very wet area of the west coast of Scotland. When it rains the peaty soil of the hillside soaks up the rain and it all flows downhill and through the wire netting of the fence with a sizeable amount ending up in his raised flower bed. There is a fairly primitive unlined ditch further up the hillside which does help some but not enough. He is planning on digging out the existing soil and lining the back face of the bed with a continuous sheet of heavy duty black polythene,then re-filling with soil. He hopes to divert the water this way.Do you think this will do anny good or would it make matters worse? What would you advise? The hillside slopes 15-20 degrees down to the back of the garden. Thanks in advance.

forum answer Tony McCormack - Apr 23rd 2001
Hi Grant,

from what you've told me, I would suggest using an interceptor/collector drain at the boundary of the property, and have it outfall to a ditch safely away from the garden. Depending on the exact site conditions, a fin drain might also be suitable. Have a look at the drainage section of the site for more info on both these types of drain, and let me know if you need more info.

Forum Question Garden Drainage - Justine Chapman - May 21st 2001
Having just purchased our house two weeks ago, we have found that we acquired a large swimming pool in the back garden when it rains. We have had the council to check for drainage problems in their pipes and even had the water board out to check for any leaks (just to satisfy us that the problem is land drainage). These both came back clear.

We have had a company out who suggest putting in three 2ft deep trenches down the garden and then run a 'french' drainage system from it to the main drain. Although we are still awaiting the price the indication was that it was very expensive and disruptive. Can anyone suggest whether there may be a less intrusive type of drainage system that may help.

forum answer Tony McCormack - May 21st 2001
Hi Justine,
Done properly, a land drain (aka a French Drain) is not frighteningly expensive and is not too disruptive. It's certainly the simplest solution.

Depending on local conditions and the amount of work to be done, a collector drain normally costs between 8-15 quid per linear metre installed when less than a metre in depth.

You don't sound terribly confidant with the contractor you've called in. You should always get at least 3 quotes for any work of the nature; if the contractor know there is only them up for the job, you run the very real risk of being ripped off! Get at least 2 more quotes before giving anyone the go-ahead to proceed with the work.

Forum Question Wondering about water tables - Alan Simpson - May 22nd 2001
Just wondering about water tables (as I wrote in the subject header). It couldn't be just 18-21 inches below the surface, could it? In North London??

There is a cellar about 4 or so feet deep under my house and while the "floor" is sometimes damp, it is never sloppy like that clay in my rear garden, nor flooded at all, let alone flooded over 2 feet (i.e., within "18-21 inches below the surface").

Could there really be such a discrepancy in water levels within the 20 or so metres between my cellar and the sloppy clay? But I do wonder (no, it's called worrying, Alan) as the New River runs within about 200 metres of my house and an underground stream runs behind the properties on the other side of the street (i.e., within about 40-60 metres, roughly).

You'll have to excuse me while I dwell on this matter of the sloppy clay and how deep I'll have to dig to get to the below the sloppy bit. Hell, if I didn't have something to worry about, then I'd be a happy man: what fun would that be?? (Please Lord, let me someday find out!!!).

forum answer Tony McCormack - May 24th 2001
The purpose behind excavating and removing the sloppy clay is to prevent it 'running' once the concrete is in place, contaminating and weakening the mix. Take out as much as possible just before you pour; in the spots where it's impossible to shift it all, you could 'stiffen' it by stirring in some cement the night before youy intend pouring, seeing as this is only for a garden wall and not a critical, load-bearing wall. smiley

A BCO would have you take the lot out!

A water table can be very shallow, but, with me living in the big metropolis of Warrington, I'm not familiar with this liitle village you mention (Lundun, did you say?), so I can't say exactly what you should expect, but I wouldn't anticipate such a dramatic change in level over such a short distance.

Could there be a leaky water service nearby?

Forum Question Patio Drainage? - Tony Benham - May 23rd 2001
I am going to build a small courtyard in the space between the side of my house and the party fence to our neighbours. This should need water drain(s). But I have found it difficult to determine what sort of system the house uses already to dispose of rainwater from the roof. The house was built in 1984, and all the downpipes from the gutters just go straight into the ground. There are 2-3 small concrete square access hatches along the walls of the house. Would this be a separate surfacewater / foul water system ? So the downpipes all link into the surface water system, and the small hatches give access to that drain system ? Presumably then my courtyard would need a drain/gully fitted into that system to drain the water away ? How are the downpipes typically connected into that type of system. Your website shows the use of gullies, which are open, but we only have these where the utility/kitchen wastes come out of the house.
forum answer Tony McCormack - May 24th 2001
Hi Tony,
given that your house is fairly modern, it is almost certain to have separate foul and surface water systems, therefore, your additional drainage should be connected to the existing surface water system, either via a new access or inspection chamber, or via a branch junction. I'm working on an updated version of the drainage pages dealing with new connections at the moment, so I'll send you the url by email, as the pages aren't complete just yet and many of the links will not work for the time being, but it will enable you to see in more detail just how connections can be formed.

If that doesn't help, post back here and I'll see what else I can do. smiley

Forum Question - Tony Benham - Jun 8th 2001
Thanks for the reply. I'm still puzzled as the connection of our gutter down pipes which go straight into the ground. They have what look like plastic caps at the bottom presumably to allow access for clearing blockages ? Do they connect straight into the surface water drains underground ? What sort of fitting is this, I couldn't find an example of this on your site ?
forum answer Tony McCormack - Jun 8th 2001
Hi again,
your fittings sound like simple access fittings. Is there a manufacturers name visible or can you get a picture for me to view?
Forum Question Garden Drainage - Justine Chapman - Jun 8th 2001
I wrote to you on the 21st May with regard to the problems we were having with garden drainage. You replied the same day and gave me some outline prices for the work to be done.

You advised that we could expect to pay between £8 and £15 per linear meter for the work, we eventually got the quote (after 4 weeks) yesterday and the charge is £1950 inc. VAT for 46 linear meters being dug a max of 450mm depth and then connecting to the main drain. With all the excavated materials to be left for us to clear away.

My two questions this time are: firtstly I think this sounds rather expensive do you agree? and secondly trying to find someone to get comparative quotes in the Manchester area is proving rather difficult . It could be that I am just looking in the wrong area or for the wrong type of contractor - could you advise of anywhere that I may be able to obtain a list of local contractors to carry out this type of work.

Many thanks once again for reading this.

forum answer Tony McCormack - Apr 2nd 2001
That price, and the delay in getting it to you, strongly suggests that the contractor is really not interested in doing the work. That's working out at 36 quid per linear metre, plus VAT, which compares badly with the current 'going-rate' for 100mm clayware sewer drainage, 1 metre deep, which is around 27-30 quid per linear metre for small private jobs.

Your man is trying to rip you off!

Whereabouts in Manchester? Contact me by email, and I'll see if I can put you on to someone who might be able to help.

Forum Question - Justine Chapman - Jun 11th 2001
Hi Tony,
Thanks for getting back to me so soon. I live in Timperley, Altrincham which is South Manchester.

Thanks for all you're assistance and for confirming what we suspected. I look forward to receiving details from you in due course.

Forum Question Draining Uphill - Jo - Jun 24th 2001
Tried to build a soakaway to cope with excess water accumulating on the drive right next to the house. Unfortunately, after 8' of solid clay, just found even more clay! The nearest drain is approx 2' higher than the point where the water is collecting so we need to drain 'uphill'. Thought we could backfill the soakaway and use some sort of sump tank with a pump to transfer water to the drain. Does this sound feasible to you? Do you know of any products on the UK market that would be suitable for this? Or maybe you have a better idea! Please help - getting desperate!!
forum answer Tony McCormack - Jun 24th 2001
Why did you opt for a soakaway, Jo? Do your neighbours rely on soakaways or are they common in your area?

Anyway, when you say the nearest "drain" is approx 2' higher than the low point on the driveway, do you mean the cover of the drain or the invert level?

Pumping water uphill is a bloody expensive business. You'd need a sump chamber, with a pump and a float switch, plus a rising sewer to pump the water along until it reaches the main surface water system, then a trap to prevent the SW system surcharging into your really has to be a last resort. Is there no other drain point nearby, even if it's on a neighbours' property or even in the carriageway?

Forum Question - Jo - Jun 26th 2001
Thanks for your prompt reply. Husband decided soakaway would be the best solution because of lack of access to drains. This is now definitely off the cards due to the clay and as the pump idea also sounds too expensive and complicated, I guess we need to sort out some way of channelling the water to the drain round the back of the house.

Our biggest problem is that the lowest point where the water is collecting is right against the house, we don't want to build up the paving at this point because this will cover the damp course. The top of the drive is a good 18 inches higher and slopes in towards the house. there may be a possibility of building a step up to the drive and turn the lower part where the water collects into a path. It might then be possible to run a gully along the bottom of the step and take this round the back of the house to the rear drain. The gully will need to run directly against the house wall (below the damp course) when it gets to the rear of the house because we've already block paved this area. We'll also need to lower the ground at the point where the front meets the back as this is also currently higher than the point where the water collects. Looks like there's plenty of spade work ahead and we've also got to fill in that 8' hole!!

forum answer Tony McCormack - Jun 27th 2001
It sounds as though you need a linear drain laid tight against the house wall, Jo. Have you thought of getting a local builder/contractor around to take a look and give you some onsite advice?
Forum Question House drainage query - Carolyn Austin - Jul 14th 2001
We are buying a new house in a small development of three houses which is nearly completed. My house is 3ft lower than the adjacent house with a sloping gap of 12ft (of just soil) between the houses. I fear that my wall could become damp due to water collection. The dividing fence is 6ft away and I believe the soil tends to be clay. Yor site shows how to alleviate the drainage ie. gully or soakaway.
Can a builder reasonably ignore this problem ?

Are there any regulations covering this situation or, what is recognised good practise that can be expected? Whose responsibility is it? What would you advise is the best method to deal with the drainage?

I have found your site enlightening and extremely helpful - thank you.

forum answer Tony McCormack - Jul 16th 2001
Mmmm. A soakaway isn't going to be of any use - a gully or linear drain may help, but there should be no soil lodging against your brickwork full stop. The ought to be a gully or other drainage point already in position against the brickwork of your property to take away any surface water that accumulates there. Also, there is a mandatory 150mm clear zone between ground level and the damp proof course, so, even with the significant slope towards your property (1 in 4) there should be no danger of water 'ponding' against your property.

Can a builder reasonably ignore this problem ?

No. The Building Control Officer should spot any shortcoming and will insist that any defect or breach of Building Regs is corrected.

Are there any regulations covering this situation or, what is recognised good practise that can be expected?

As stated above, there should be a gully or other drainage point on the lower end of the slope to protect your property.

Whose responsibility is it?

The builder, for now.

What would you advise is the best method to deal with the drainage?

Personally, I would prefer to see a drainage composite, fin drain or linear drain installed approximately 1 metre away from your property, so that the entire 12' gap between the properties drains into that, rather than allow surface water to lodge against your brickwork. If this was set, say, so that there was 50-75mm of fall away from the wall of your property, there would be no chance of surface water causing any problems.
Forum Question Salt-Glazed Drainage Channel - Gordon Clark - Jul 18th 2001
I am trying to locate a supplier of traditional brown, salt-glazed, semi-circular open drainage channels for domestic use, of the type that used to be very common but which I am having great difficulty in finding. Can anyone help? The use I have in mind is a rill as part of a water feature.
forum answer Tony McCormack - Apr 2nd 2001
Salt-glaze pipes are not manufactured any longer, so your only likely source would be a reclamation yard or a drainage contractor who is ripping out salt-glaze and replacing with new.

Whereabouts are you, Gordon? There are some good salvage yards up here in NW England.

forum answer Gordon Clark - Jul 22nd 2001
Thanks for response. I live close to Coventry. Any suggestions?
forum answer Tony McCormack - Jul 22nd 2001
There must be salavage yards down there, Gordon - try SalvoWeb or look in the Yellow Pages for Architectural Salvage or Drainage Contractors.

Good luck! Let me know how you get on.

Forum Question New Drain - Mark Davies - Jul 23rd 2001
I am renovating my house and am creating a new bathroom which requires a new drain for the waste. There is an existing inspection chamber at the end of the drive that could be linked into. My question is what kind of contractor would I require to do this work, plumber or groundworks or other.

Also would they typically dig up the concrete drive (which I wish to block pave) or would that be something I would have to do beforehand.

forum answer Tony McCormack - Apr 2nd 2001
Hi Mark,
normally, a plumber undertakes the above ground pipework and a drainage contracor or groundworker takes on the underground stuff, but there are good contractors who can do both. While many contractors will be happy for you to do the hard excavation work for them, they would be able to do as much or as little as you require. Bear in mind that excavating concrete is bloody hardw ork and a cometent contractor will have all the right kit to make the job as easy as possible, whereas you could find yourself working your proverbials off, just to save 50 quid.
Forum Question French drains - Guy - 30 May 2002
Finally found a contractor to install a block patio in the rear garden of my victorian semi in Battersea and settled on Bretts Beta Autumn Gold - thanks for your guidance. My builder is somewhat worried about the DPC levels but if we go down 150mm my patio would drain the entire street! Builder suggests French Drain and have researched what I can. Seems there are two types, one with a drainage pipe and one without. Technically the French is with shingle only and it is this which I have specified for circa 100mm adjacent to the property. What are your thoughts on the matter???

Many thanks as usual...


forum answer Tony McCormack - 30 May 2002
To where will this French Drain drain? If there's a suitable outfall, why not use a linear drain or a conventional gully rather than a 'last-resort' french drain?
30 May 2002
I guess it will really be a simple soak-away as it would drain vertically into the sub-soil. What started out as quite a simple job, or so I thought, is getting bigger the more I find out. There are two sewage drains at either edge of the 'garden' one along the side-return the other by the kitchen door where I assume the outside loo might once have been. How much am I looking at this time????


Tony McCormack
30 May 2002
Soakaways are all well and good as long as they actually 'do what it says on the label', ie, soak away. All too often, what was hoped to be a soakaway turns out to be a hole filled with water. sulk

Have any percolation tests been done, or do you know for a fact that the sub-soil is very free draining, Guy?

If you have existing drainage, I'd tap into that, as then you know the water will be drained away and not left hanging on the paving. Cost-wise, a proper drainage connection wouldn't/shouldn't be much more than the cost of a French Drain. 50 quid or so for a connection, pipework is around 20-25 quid per metre and a linear drain can be bought for around 10 quid per linear metre. Ask your contractor to price it as an option - there's no harm in asking. smile

Forum Question Fixing dpc around an internal inspection chamber - Sev - 21 June 2002
We are building an extension. As a result we have to move our present (external) manhole cover and inspection chamber. We want to use one of the modern plastic chambers rather than create our own brick and mortar one, but can't find any information about fixing the dpc up to or around or under it.

Can anyone help?

forum answer Tony McCormack - 21 Jun 2002
Hi Sarah,

I don't understand - why would a dpc have any connection with a plastic IC? You only have a dpc in the brickwork of the house walls - why do you think it would be a problem with a new IC?

22 June 2002
The floor will have to have dpc under it, but the IC will be in the middle of the floor! We don't know where the dpc needs to go around/under/on the IC, or indeed how to fix it to stop any dampness creeping up between the edge of the dpc and the IC itself.
Does that make any sense?!
Tony McCormack
22 June 2002
Aaah - you mean a dpM - a damp proof MEMBRANE - a dpC (damp proof COURSE) is used within walls.

If you are planning to incorporate a drainage IC within an internal floor, first, you must have the drainage plans approved by your local Building Control Officer and second, you will need to use a double-seal IC cover to prevent any gases or odours arising from the sewers.

The dpm is laid up and around the IC, trimmed to suit. It's not critical if it just touches the sides of the chamber, or if it comes, say, 50mm up the sides. The purpose of a dpm is two-fold - to prevent the concrete being dried out by the sub-base and to protect the concrete from any 'corrosion' from beneath. A gap of 25mm or so around an IC is not the end of the world. smiley

Forum Question Standing water - Snowcat - 15 Aug 2002

Not sure if you can help, but my neighbour is being very difficult regarding standing water in our back garden. We live on the side of a 1 in 4 hill, so any water from our garden naturally drains onto hers, being lower than us. We have a paved garden with a small wall on the opposite side to our neighbour with a lawn & rockery sloping down to the wall. When it has been raining we do get puddles on the paved area, but it couldn't possibly be called flooding. However, she insisted that our drains must be blocked, so we rodded the drains only to discover that they were fine. She also called out the water board last winter, but I assume they told her everything was fine as they didn't contact me. Now she is trying to get the Environmental Health agency involved - I appriciate that the drainage on the paved area probably isn't great, but should I really consider ripping it up & relaying it just to keep her quiet or will it make no difference? pics of the house & garden are on my website if it helps.

forum answer Tony McCormack - 16 Aug 2002
Having taken the extensive (and exhausting!) tour of the Mansion House, I reckon you should install an interceptor at the boundary between your lands and the adjacent property.

There are two types of interceptor that you could consider - a surface interceptor, and a sub-surface type. The sub-surface type is normally used when there are problems with groundwater draining into an area, but you neighbour's concern seems to be regarding the surface water, so I'd opt for a surface interceptor.

The two simplest types of surface interceptors are Dished Channels, as illustrated on the Road kerbs page or the Linear Drains described in the Drainage section of the site.

Lay these on a concrete bed and haunch, as shown, and connect to the nearest SW drainage point, which will probably be a gully or rainwater pick-up. Dished channels, of the decorative type, cost around a tenner per linear metre, and you can get a cheap linear drain for that sort of price from B&Q or HomeBase.

The Environment Agency have a special team to deal with 'over anxious' callers who plague them with complaints about impending disaster only to find the lake on a neighbouring property is actually a bird bath, and the industrial extraction unit is a kitchen Xpelair!  wink

Forum Question Blocked Soakaway - Tony - 28 Feb 2002
Hi - I have a basic guttering question. After cleaning out my gutters this weekend (as a result of water pouring over the centre of a run of guttering when it rains) I have discovered that one of the downpipes is blocked. I have pulled a load of leaves and gunk out of the top 3" (as far as my fingers will go), but think that the whole length of the downpipe is blocked. The downpipe goes into the ground into a soakaway, my question is - can I cut off the bottom 6" of downpipe (2.5" x 2.5" black plastic pipe) which will allow me to force all the gunk out of the bottom of the pipe from the top. I could then fit a 90 degree elbow to direct the water into a flower bed - OR - should I replace the whole length of downpipe, if so, how deep would I need to dig to enable the pipe to be removed ? and is there any special preparation I need to do to the soil before burying the new downpipe ?? - great site by the way, will definitely be returning for info when I lay my drive later this year.


forum answer Tony McCormack - 28 Feb 2002
Hi Tony,

I'd be tempted to saw through the downspout 100-150mm or so above ground level just to see if the downspout is blocked solid or whether it's just blocked at the top end, where the gutter hopper is. Then, if it's not as bad as you think, the downspout can be jointed back together with a coupling (if you can find one for that range of above ground pipework) once you've cleared the obstruction. Alternatively, use a shoe and discharge into a Hopper or Gully (see below)

However, if the blockage is below ground, causing the detritus to back-up, then you're going to have to dig down and follow the pipework until you find the cause and then fix that according to what you find. If it's just silting-up through years of use, you may be better off replacing the entire pipe run rather than trying to salvage what's there. If it's a broken/collapsed pipe, you might be able to repair. If the soakaway itself is choked.....uh-oh! Time to start again. sulk

Whatever the cause, you might as well take preventative measures to avoid this happening again in a few years time. Fit a litter trap into the hopper of the guttering to keep out leaves and mosses. Consider fitting a P-trap and hopper or a yard gully at the foot of the downspout to act as a catch-pit for any bulky crap before it gets to the soakaway, rather than piping straight through, and, if you do end up having to re-pipe the drain, incorporate a rodding eye or access chamber so you can get at the underground pipes without having to dig everything up.

I can't tell you how deep the soakaway will be, or how far the downspout will travel beneath ground level before it meets the drainage system, as each situation is unique and there are no set standards. I can tell you though, that discharging onto a flower bed is a very, very last resort. If the roof area being drained is greater than 10m², I wouldn't even consider it unless the house was built on sand/gravel and know to have excellent groundwater drainage.

Let me know what you find.

28 Feb 2002

Thanks for the comprehensive reply - I was getting myself pumped in the week to start hacking through the downpipe, when I spoke to the maintenance guy at work over lunch about my weekend job. He said that all the private work he had done on problems with blocked gutters had been caused by a blocked downpipe right at the very top of the downpipe (the bit directly under the gutter that goes vertical then 45 degrees in towards the wall then vertical again to align with the downpipe). He said that these are a push fit so should be easy to disassemble once the gutter is unclipped from the supports and the downpipe to wall brackets are loosened. So I did this and to my relief found that the short angled section that I had removed was solid with hard dark brown gunge, leaves and the skeleton of a small mammal, and that shining a torch down the downpipe revealed that it was clear. After a ½ hour soak in hot water, the gunge was flushed out no problem. So it looks like I'm sorted !
- while I was up there I fitted litter traps to the openings on both downpipes (front & rear of the house) so should not get the same problem in the future.

Thanks again for the advice, I hope it rains hard soon to make sure that was the problem.


Tony McCormack Good to hear you got it sorted, Tony. smiley
Forum Question Patio/sunroom drainage - Tony Jackson
I had a sunroom installed on an existing concrete slab patio. It unfortunately is at the low end of my back yard and runoff ends up seeping into the sunroom when an extremely heavy rain occurs. Is there a way to create a drain at the low point in the slab before it reaches the sunroom wall?

Tony Jackson

forum answer Tony McCormack
Hi Tony,

the usual remedy for this sort of problem is to cut a channel in the concrete slab and install either a linear drain or some form of kerb channel, such as the Keychannel by Marshalls, and direct that to the nearest gully.

You'll need a Power Saw to cut through the concrete, and the linear drain or channels will need to be bedded on concrete or mortar to a level of around 3mm below the concrete surface. You can then patch in around the newly installed drain/channel with fresh concrete or a grano mix.


Forum Question Water Egress - Mairi MacKay - Jan 11th 2001
We hope you are the help we've been looking for!

For the past 3 years we have been experiencing (usually during/after some wet weather) water emanating from the bottom of our driveway and flows across the pavement and down the road. The house (1930s build) is on a slight incline, and the stone wall which borders the driveway has small 'slits/gaps' to allow water to flow. Unfortunately - possibly due to new houses being built higher up the hill, it would appear that a stream may have been blocked / diverted. This has caused an increase in the flow of water - which freezes in winter, causing problems (one neighbour is currently suing us as a result of an accident on the ice). We have contacted the local water authority and local council (who have now served us notice to 'sort it out') who both claim that this matter is nothing to do with them. The Environment Agency state that this is just 'an act of God' and that there is nothing that can be done - water runs downhill!

This leads to my question - Obviously this water is causing further damage to an already crumbling driveway and it is my intention to lay a block paviour drive. Do you think it is:
a) possible to 'divert' this water without taking the wall down and digging up the front garden and
b) how can this water be diverted under the driveway and off my property?

Clearly, in the absence of any support from the relevant bodies, we are wary of spending money, which will not cure the problem. Can you advise where we should seek further assistance.

Thank you
Mairi MacKay

forum answer Tony McCormack
This is exactly the problem being experienced by a certain DIY retailer in Warrington. What is happening is that groundwater is 'flowing' beneath your driveway and is escaping at the foot of the driveway. This may be because the drive intersects the water table, or it could be because of a naturally occuring spring line - whatever the reason, that's what is happening, and it's not all that difficult to cure, you'll be glad to learn.

You need to intercept the groundwater before it reaches the foot of the driveway. This can be done by use of an interceptor or fin drain (see land drainage section of this site), or via a drainage composite. These must then discharge into the existing drainage system - you cannot rely on a soakaway, given the existing ground problems.

Once the drainage is sorted out, you'll have no problem installing and maintaining a block paved driveway, and you should have no further problems with your neighbours. smiley

Have you spoken to any local contractors about your plans? The site needs to be investigated before the most appropriate remedy can be designed and implemented.

Forum Question Flooded garden - Les Davis
Hi Found this site through Excite. Its Brilliant and the answer to my prayers. Wish id found it a year or so ago.

My problem is that I've got an old cottage about 100 years old its seems to have been built in a hole. The water table is very high about 300 mm below ground in winter. The area around has land drainage and this drains into a Catchment pit ( as per your Web-Page). My storm water also goes into the pit then it is dispersed into a ditch through a 6 inch clay pipe about 500 metres away. This pipe runs through several neighbours property and access is very difficult.

The problem is whenever we get heavy rain in winter the water backs up and floods my land. The end of the pipe is submersed in the ditch. Would this restrict the flow?

I pump this water away by putting the pump in the catchment pit . Would it be advisable to build a bigger pit and permanently leave a pump in there on a float switch to pump away the excess water. Your thoughts please

Les Davis

forum answer Tony McCormack
Hi Les,

If the outfall of the drainage pipe is submerged, then it will affect its ability to drain - in effect, the water in the ditch will surcharge into the pipe and travel towards your land.

When you pump out your catch pit, where do you pump the water to? Into the Foul System?

When it comes to building a bigger storage reservoir, you'd really need to understand the local hydrology. You could end up providing spare capacity for all your neighbours and the ditch, while not gaining any benefit for yourself. A pumped storage facility, what we call a wet well, discharging into the FW system may need a consent from your local authority, just depending on what the local flood plan is.

A one-way valve or penstock on you discharge pipe may be a simpler answer. Have you spoken to any local drainage contractors?

Les Davis Tony

Thank for your quick reply.

I haven't contacted any drainage contractors because I had a bad experience when I first moved in and had a new Septic tank fitted (major cockup). Resolved now

I am in Sussex could you recommend anyone.

The local council have agreed to dredge the ditch so that might cure the problem .If not I'll try a one-way valve as per your suggestion and if that doesn't work I'll be in Touch (Lol)

Thanks Again

Tony McCormack
I don't know anyone 'firsthand' in Sussexshire, but I have a few contacts in the civils trade down there that might be able to put us on to someone - friend of a friend and all that!

Let me know how you get on.


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