Crofter Posted August 29, 2016 Share Posted August 29, 2016 I'm trying to finish off my flooring and need to work out what the waste runs are doing. The floor is suspended, on 300mm deep JJI joists. There is limited space underneath these- maybe 200mm at the most, in the part of the house where the watse runs are. My plan is to have the main runs underneath the house, rather than within the joists- so I am looking at having a drop of about 350mm from the shower tray to the start of the horizontal run. In which case, where should I put the trap? Just wondering what might be the easiest or neatest way of doing this. It must be the same setup as @ProDave ? Link to comment Share on other sites More sharing options...
ProDave Posted August 29, 2016 Share Posted August 29, 2016 I can't help you directly as although my ground floor joists are 300mm JJI's, I am only making "provision" for a downstairs shower not actually fitting one. So I am just going to provide a 4" branch off the main stack with it plugged off. The 4" pipe will be just under the JJI joists so I guess if I ever fit a shower it will have the trap in the normal place then out if the trap into a 90 degree bend and straight down to a reducer into the 4" pipe. Link to comment Share on other sites More sharing options...
Temp Posted August 29, 2016 Share Posted August 29, 2016 The danger with a large fall is that the water can get sucked out of the trap. I think I'd still use a top access trap unless you want to have to go under the floor to clean it out. Perhaps test installation somehow before laying the floor etc? Link to comment Share on other sites More sharing options...
Crofter Posted August 29, 2016 Author Share Posted August 29, 2016 Thanks Dave, I don't know why I hadn't thought of having a normal trap then a 90deg bend to take it through the floor. This would actually give me much more flexibility in positioning everything. Temp- that's useful to know, thanks. I can't test installation as I have to finish the floor ASAP and the shower fittings etc are a long way off just now. Link to comment Share on other sites More sharing options...
Nickfromwales Posted August 29, 2016 Share Posted August 29, 2016 6 hours ago, Temp said: The danger with a large fall is that the water can get sucked out of the trap. I think I'd still use a top access trap unless you want to have to go under the floor to clean it out. Perhaps test installation somehow before laying the floor etc? +1 just bring the 110mm pipe up as far as you can and then fit one of these Link to comment Share on other sites More sharing options...
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