Routing a waste pipe around the extension

14 Jan 2013
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United Kingdom

I’m just embarking on a new project and I’m stuck already!

Mid-terrace house with an extension at the back. The extension (single storey) contains the family bathroom and the waste pipes from this feed straight out the back of the extension, into an IC and onwards.

The project is to install an upstairs shower room. We want to convert the old box room into the shower room (and that’s where we want it, between both bedrooms).

The shower room will have a shower with 40/50mm waste pipe, basin with 40/50mm waste pipe and toilet with 80/90mm waste pipe. The joists are 170mm, so it should be ok to achieve the necessary gradient running through the house.

The problem is how to reach the IC at the back of the house. The extension has a pitched roof, and I just can’t think of any way to route a waste pipe around it! Any suggestions?

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Through the roofspace? It would have to cross it diagonally as well as achieving the gradient. What are the pitfalls to look out for?
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If the soil pipe exits the wall of the 2 storey then what level is that in relation to the new single storey extension?
Is there a valley guttering between the back of the terrace and the extension?
A side elevation plan would be helpful.
Also what way are the joists running? Looks like a tricky job.

When the extension was being built that was the time to do the feasibility study and take it from there.
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As long as an adequate fall is achieved along the entire run, then a couple of 45° bends shouldn't be too much hassle I wouldn't think. You will need to ventilate the top end though at the WC, an Air Admittance Valve should suffice for this purpose.

I'd also look at fitting at least one access point, ideally on the bend where the pipe turns to drop downwards at the end of the building.

How and where are you planning on connecting to the existing sewer?

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