pintail120 said:
thank you for your comments, if possible I would like some more info. The current waste pipes from the bath and basin run horizontal. The flat was bought like this, (1)should I change the fall on these pipes?
Ideally, yes. Otherwise, sooner or later, you'll have smells and blockages.
Everything has worked since we moved in 4 years ago and never had any problems.
I understand and sympathise, but I'd like to have had £1 for everytime someone said to me "it was working perfectly yesterday".
I saw those pipes were run horizontal and I assumed I could do the same with the showers waste pipe. Biggest mistake humans make is assumption and I am doing that now.
Too true, but a bigger mistake would be not to ask questions, and you're not making that one.
(2)Please explain how raising the shower tray will allow me to have the showers waste pipe horizontal?
I merely meant that you can't lower the pipe at the stack end, then you'll have to raise the pipe at the tray end. This means that you'd have to raise the tray, which is fairly commonplace when installing a new shower.
Back to the real reason I was thinking of using the hepvo: As I intend to join the showers waste into the baths waste pipe. Even if I implimented a fall of 1 inch per meter on the showers waste pipe, I was thinking that when the bath empties the water would be tempted to flow back up the showers waste pipe for the following reasons:
(a) They are using the same waste pipe and the shower tray would be at the same level of water in the bath if not lower at some point.
I understand your reasoning with that, and if the pipes were horizontal then that's exactly what would happen.
(b)It stands to reason that the shower tray would have to be higher than the water level in the bath for water not to flow back into the shower tray. This would not be logical or practical to impliment.
Er, yes and no. The shower tray surface would be significantly higher than the outlet of a standard shower trap, and on top of that the trap presents resistance to backflow.
(3)Do you think it would have purpose in that configuration?
I really don't. Its primary purpose is to prevent backflow of air and other gases. If your design allows water to sit in the pipe around the HepvO, then it will only be a matter of time before the whole kit and caboodle gunges up.
(4) is it ok to run the showers waste into the same pipe as the baths waste pipe? I doubt there will ever be a combination of both operating simultaneously but (a) would still like to know what would happen if they were both purging together? (b) what would happen when the bath purges on its own?
Best practice is to fit a swept tee where the bath joins the waste from the shower, and to change the waste pipe downstream of that tee to 50mm.
An example of a suitable swept tee is the W3160 illustrated on
this page.
(5) what do the building regulations state that I should correct in my design with regards to the horizontal shower waste pipe? I read some where here that it should have a fall of 1 inch every 1 meter is that right?
That's not an awful rule of thumb for short runs, because it approximates 1 in 23, which is a 2.5° fall, and more than the Marley recommended minimu of 20mm. If you want a strictly 2.5° fall, then make it 44mm per metre.
If you do this throughout then the pipe angle will be correct at the boss where it enters the stack, although most people 'cheat' by making just the last section fall at 2.5°
many thanks again for your professional help you have given, very much appreciatted
You're very welcome.
I think you'd benefit from reading the Brett Martin and/or Marley waste system installation guides, here:
http://www.brettmartin.com/building/soilwaste/technical_guide/design/soilandwasteinstallation.aspx
and here:
http://www.marleyplumbinganddrainage.com/images/productguides/Waste & Overflow1.pdf
