advice drainage/soil pipe for new upstairs en suite

6 Jan 2007
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United Kingdom
Hi folks,
fitting an en suite to upstairs conversion in a bungalow.
Need some advice on drainage and soil pipe configuration.. (I've fitted bathrooms etc, pretty good but totally new soil pipework is new for me..!)

Only pipework is downstairs at the moment. The original (old) plans for upstairs allow for an en suite so could maybe get away without warrant (don't have time to apply anyway) but I would want to ensure it complies in case I need to register the work at any point. (I've downloaded part H and had a look..)

New en suite is in small room off bedroom with velux already. (So no vent needed.) I want to fit a shower, toilet & sink.

Supply pipework is no problem, it's all mains fed / combi, can run pipes no problem. Question is with soil pipe..


1. It's more or less above the downstairs bathroom, so could run a soil pipe and box in to corner of bathroom but a bit limited for space in bathroom, would prefer to run down OUTSIDE wall of house. Is this OK? (eg: regs, freezing etc) Plan to maybe take pipe out through eaves & down through soffit and down wall? (The en suite room is against the outside wall so not far for any pipes to run)

2. What about ventilation for soil pipe? It should have an open vent at the top but this needs to be well above the toilet height, so would stick above the roof line? What do folk do about this? Heard about the AAV, would one of those do? If so where would I fit it, if not what do I do?! There is a velux like I said so an external vent needs to be away from that, so can I extend horizontally on the top of the outside wall before taking a vent up if I need for max distance from window?)

3. When fitting the shower, the shower tray will be below the level of the toilet outlet obviously, so how do I connect the drain from the shower without causing problems? Do I need to run a completely separate drain pipe (like normal 40mm solvent pipe) out the wall on its own and connect it to the soil pipe separately from the toilet connection which will be higher up? Or can I somehow connect it internally in the en suite and have just the one pipe going out the wall?

4. What's the best trap configuration for the shower tray?

5. I have a cellar so can easily access the existing soil pipe under the floor and was planning on running the new soil pipe from the en suite down the outside wall, then back in the the house into the cellar where i can connect it easily to existing soil pipe without digging up the ground. i know I'd need to use the wide radius bend at the bottom of the drop before it comes back in the house but any issues other than that?

6. Anything else I haven't thought about??!!!

Thanks folks, that was long!
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