Surface water running into foul drain - is this ok?

2 Dec 2012
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United Kingdom
I'm doing a bit of work at the minute in preparation for a new drive, and plan on installing some channel drainage at the front. I have got an existing drain to the front for the canopy's gutter (but in totally the wrong place!) and also one at the side next to the car port's concrete slab. The main roof guttering drains into next door's drains front and back. Having looked through the old planning documents for the house from 1971, it would appear I only have a foul connection, but next door have foul and surface pipes hence why they take the roof rainwater at their side. There's only one manhole cover as well in my back garden which I'm told suggests foul only. I haven't been able to lift it just yet as there's a load of spoil on top of the lid that needs clearing.

I've done a bit of digging around the two existing drains I've got, neither of them are deep under the car port slab (<100mm from FFL), both use a U bend, and both are 4" socketed clay. I suspect they were laid by whoever built the car port, which was possibly the people who built the house. Is it considered acceptable to drain surface water into the foul drain like this, when a surface drain does exist? According to the plans, I have no storm drain pipe on my land, and digging across to next door to pick it up isn't an option. A soakaway isn't an option either as we have plenty of clay and are on a raft foundation. I have access to STW plans at work so will check if the foul and surface combine at some point but I suspect the surface drain carries on to the river not too far away as it's pointing in that direction and there is an outfall in about the right place...

I've attached a section of the plan with a bit added by me, the blue dot is the internal soil stack and the assumed route of the pipe, and the blue square is the manhole. The red dots are the outside drains and the assumed route of their pipes.

If this is OK to leave as is, my plan is to divert the drains to the side and front well away from the car port while I'm messing about, so when I come to extend the house over it in the future I've got a clear run. I suspect I would have to start from the manhole and work back to get a decent depth. While I'm at it I may as well replace the internal soil stack with an external's amazing how the small jobs turn into something massive.

Thanks in advance

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It is not unusual for B.C to as for a soakaway even if a STORM system exists on the property, let alone a foul system. As long as the ground is suitable, the L.A. will always look at a soakaway option first.

If your ground is clay and there is no dedicated storm system then it is deemed acceptable for you to use the foul system once all other options have been ruled out.

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