Surface water into foul drain?

4 Jan 2011
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United Kingdom
Hi all,

We're doing an extension across the back of our 1950's mid-terrace house.

We have a shared foul drain with our 1st neighbours.

They've done a similar extension to what we're doing but have their surface water run into a soak away. The trouble is that we've got clay soil so their soak away isn't the best and our garden gets boggy when there's rain (maybe from their soakaway?) so I really want to avoid having a soak away if possible.

The problem is the surface water pipe that goes into our 2nd neighbours garden is an old clay one and we've realised that it's blocked and probably broken somewhere along under the 2nd neighbours garden (the bit that we exposed in our garden has cracks in many places).

So we don't really want to connect our surface water to the pipes that run under the 2nd neighbours garden as that will be asking for trouble.

Can we run the surface water into the foul drain instead do you think? I can't tell if you can never run surface water into a foul drain or if you can as long as a soak away isn't possible.

On our plans the surface and foul water all run into the man hole drain.

I hope this makes sense! Thanks in advance.
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The best for the environment, and the cheapest method (you can claim a rebate on your water bill) is to run your surface water into a sump on your property.
Thank ree.

Is a sump the same as a soak away? Trouble with that though is that our soil is clay so water takes a long time to drain away.
So you seem to be saying the private surface water drain is blocked and you’re just gonna ignore it? Even though it may be contributing to your garden drainage issues? And you want to feed your new surface water into the foul drain to avoid the issue?

Building Control will first of all ask that a soakaway be constructed, if the BCO is familiar with the local area (most are) he will likely say straight off if soakaways work in your area or not, if its clay they probably don’t.

So then they will allow you to drain into the surface water drains, assuming they can cope. Firs off he will expect you to drain into the SW drain on your land, what do you suppose he will say when you say that may not be such a great idea because you know your drain is caput? Do you suppose he will say oh well not to worry Poppet and pat you on the head? Or will say buck up and get the the bloody thing sorted?

BTW once your own private SW drain leaves your boundary it becomes the responsibility of your water company so you only have to fix the bit on your land, the rest is down to the water company to repair.
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I'm not ignoring it! It's not in our garden that they're blocked/cracked, it's further along under the neighbours garden. We've told them that the pipe is blocked/cracked and suggested they contact their Housing Association for advice.

The surface water pipes have been removed from our garden now (BCO told us to do this as they are now redundant). There's only about 2 inches remaining near the boundary.

They were clay pipes 60+ yrs old so most of them were cracked etc.

The BCO said that we can tap into the existing surface water drains (at the bit near the boudary) as long as they are sound. He did say that he thought they would most likely not be sound and talked about blocking off the pipe at the boundary. But he didn't mention where to route the surface water if we couldn't use the existing bit.

I'll have to get the BCO back out and see what he says to do now.
Hierarchy for surface water drainage is soakaway, surface water drain, foul drain. If a soakaway isn't viable due to ground conditions then surface water drain is the next consideration. You need to find out from the BCO if he is requiring you to connect to the surface water drain before going any further.

I am assuming there is no other connection to the surface water drain prior to your boundary as you've removed the pipes, but once that drain passes onto your neighbours property I think it may then become the Water Company's asset, and they would be liable for it. Do you know where it runs from the neighbours property? Any connection to that pipe is probably going to have to be proved to be impossible before a connection to the foul drain is permitted.

It is unlikely you will be able to claim any rebate on your bill unless it can be proved all of the rainwater from your property is not discharged to the sewers.

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