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Please Help With Installing Soil Pipe Over Flat Roof

Postby Bewcs » Tue Jan 01, 2019 8:00 pm

Hi there,
let me just start by saying I am no plumber or expert and am looking for some advice on doing my first 'big' DIY project of turning a small bedroom into a bathroom, specifically with the toilet.

I want to put the toilet below the window on an external wall which is upstairs and overlooks a flat roof, the extension which is the current bathroom.
I think that the soil pipe will therefore need to go out the wall, drop down, then somehow run over the flat roof about 2.5m length to meet the stack for the existing soil (currently fitted with a vent).

I have some pics of the flat roof and wall that I want to put the toilet on and can send them on request.

I am aware that this is not ideal and should not lie flat (like next door!) and 1 plumber has already said he won’t do this part of the job.

I am guessing I can fit a T-shaped connector where the current vent is on the existing soil and then run a single piece of pipe up to wall. What would be the correct/best way to do this to ensure the pipe has the necessary drop (min 6 inches?) and is sufficiently supported?

I’ve thought of constructing a triangle ‘wedge’ shape frame from stud wall timber and thick MDF, then coat it in something weatherproof and sit this on the flat roof fixed in place with some kind of adhesive. The pipe can then sit on this all the way to the wall and be fixed in place with regular pipe brackets.

I’ve also thought of using something as ‘feet’ to support the pipe at intervals of half a meter or a meter (someone mentioned DuraFoot, maybe something like that).

Are either of these viable options?
Are there better ways I’m missing?

My ability levels are amateur for sure, but I can enlist several family members who have fitted bathrooms before to help.
Sorry for the long post but if anyone can suggest solutions and working order to do things in I’d really appreciate it!
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Simply Build It

Postby collectors » Thu Jan 03, 2019 4:37 pm

The toilet should not be any more than 10 ft from the stack & should have at least a 1/4" drop to every foot but not more than 3/4" drop per foot. Many think the steeper the flow the better. "Not true" If you have too quicker drop the water will flow too quickly & leave the solids behind.
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