'Assumed' Combined drainage

[WestcountryWonderer]

Not withstanding the old addage about assumptions...

My extension planning drawings show that the current soil stack, kitchen waste pipe and rainwater pipe are "assumed to be combined and connected to the sewer" or words to that effect.

Most likely they are assuming that the combining is done under the manhole cover that's next to them all (why they made the assumption and didnt just lift the lid up is beyond me, but that's getting off topic!)

 

If this assumption turns out to be true, would building control likely allow them to remain combined albeing probably with a new inspection chamber? or would they insist that the rainwater gets diverted to a soakaway?

We already have a soakaway shown in the back garden for the rear roof and at a push it would be possible to divert the front roof to that, but it would be a bit of a pain that would be nice to avoid if I can. Not to mention convoluted and long which opens up more chance of blockages vs a nice short run of around 1m...

 

Am I also right in thinking that if they are combined, they must do the actual combining in an inspection chamber and not tee'd into the soil stack itself at a low (under ground) level? Both instances having a trap at the bottom of the rain water pipe.

[Mr Punter]

Best to check with your Water and Sewerage undertaker if there is a separate surface water sewer in the street.

 

The preference is soakaway.  Failing this they may ask for an attenuation chamber.  Depends on extension size, soil type, available land etc.

[WestcountryWonderer]

We only bought the place at the beginning of the year and the drainage survey only showed a combined sewer, plus its a small rural village and a lot of the houses are 100s of years old rather than 10s. So I very much doubt there'd be a separate sewer hiding somewhere.

 

The square meterage is there and the ground drains well enough for a soakaway that will cope with the whole roof, it's just going to be a bit convoluted to get there from the front

 

[nod]

A couple of hundred pounds spent on a camera survey is money well spent 

It will provide you with a written and visual record of where everything is going 

[WestcountryWonderer]

10 hours ago, nod said:

A couple of hundred pounds spent on a camera survey is money well spent 

It will provide you with a written and visual record of where everything is going 

 

Sorry I wasn't very clear with the background to this - it was the previous owners who got the planning permission and for some reason they/whoever did the survey for the drawings appearently did not lift the lid of the manhole.

When I get a minute to do that, it should be prety clear as everything is within aabout 1m or less of said manhole.

 

What I'm wondering is if building control will allow existing rainwater connections to the sewer main to remain as that when the extension work is completed, or will with insist that all rainwater is diverted to the soakaway.

 

If the current drain situation isn't clear when I open up the manhole and/or building control are likely to allow combined rainwater and sererage to remain, they yes, a camera survey will ineed be worth it.

[nod]

Plus 1 with Mr P

we had a similar situation with an extension at our last home 

BC would allow us to connect them together A soak away was a cheap and easy option