New bathroom drainage

woolpeckah · 11 Mar 2006

Hi, I\\\'m converting a bedroom into an en-suite and main bathroom and need some guidance with the drainage. My idea is to connect bath, shower x 2 and basins x 2 waste for the two areas under the floor and run them all into one 32mm waste pipe which will finally run into a new vented stack. I have the clearance to create the relevant fall. Is this ok ? or should separate runs be created for each of the 5 units ?
Also is there any order in which the WC and bath etc waste outlets fix into the main stack ? to avoid any nasty smells. Thanks in advance.

tomy · 11 Mar 2006

Baths and showers have 40mm waste pipes not 32mm and I wouldt put that lot into a 40mm waste pipe Depending on distance I would use 50mm and if possible I would keep as much on its own waste pipe as possible to avoid gurgling shower trays when you empty the bath or basins

woolpeckah · 11 Mar 2006

tomy said:
Baths and showers have 40mm waste pipes not 32mm and I wouldt put that lot into a 40mm waste pipe Depending on distance I would use 50mm and if possible I would keep as much on its own waste pipe as possible to avoid gurgling shower trays when you empty the bath or basins

Thanks Tomy. that's very helpful. I've got 3 runs of approx 4m so I'm going with your suggestion of 50mm pipe. Any views on the stack order ? ie should the WC waste be above the bath waste etc ?

JPC · 11 Mar 2006

u'll need to do some research into wastes. length of run, inclines all have a bearing. u cant just join all pipes together and not increase the pipe size. it wont cope, u'll pull the water out of traps and get smells etc.

Softus · 11 Mar 2006

There is a science to it, but my general rules of thumb to avoid problems are:

1. 32mm into 40mm bath - continue with 40mm.
2. Two 32mm together - increase to 40mm.
3. 40mm shower into 40mm bath - increase to 50mm.
4. Two 40mm together (showers or baths) - increase to 50mm.
5. Horizontal (i.e not vertical) run of over 3m length - go up one size.

woolpeckah · 12 Mar 2006

Softus said:
There is a science to it, but my general rules of thumb to avoid problems are:

1. 32mm into 40mm bath - continue with 40mm.
2. Two 32mm together - increase to 40mm.
3. 40mm shower into 40mm bath - increase to 50mm.
4. Two 40mm together (showers or baths) - increase to 50mm.
5. Horizontal (i.e not vertical) run of over 3m length - go up one size.

Ok so I can create 3 horizontal runs ie 1) basin x 2 in 40mm, 2) shower x 2 in 50mm and 3) seperate bath in 40mm. Thanks for this.
I assume the stack connections order don't matter as no-one has commented. Thanks to all for your help.

Gasguru · 12 Mar 2006

Worth getting building control round before you start just to run through your proposed idea, better before starting work than risk no sign off.

Softus · 12 Mar 2006

woolpeckah said:
Ok so I can create 3 horizontal runs ie 1) basin x 2 in 40mm, 2) shower x 2 in 50mm and 3) seperate bath in 40mm.

Yup.

woolpeckah said:
I assume the stack connections order don't matter as no-one has commented.

Order doesn't matter, but there is a rule (that I can never remember without looking it up) about distance from nearest toilet discharge branch connection. If nobody else knows then I'll look it up later on.

Gasguru said:
Worth getting building control round before you start just to run through your proposed idea, better before starting work than risk no sign off.

Do what John? No reason not to talk to BCO on the phone, and clearly they will not accept stack connections that are too close (see above), but but methinks he will not be pleased to be called out just to look at some waste runs. They only want to know about changes to the underground section(s), and that there is a vent in the right place and, if an AAV is fitted, that it's high enough.

Gasguru · 12 Mar 2006

New bathrooms and pipe runs come under building control - so when you pay your fee the BCO will often come out to check proposed run (if you ask nicely) - they will often "bend the rules" if necessary in difficult situations.

I was merely stating it is better to keep the BCO on your side.

Or are you suggesting none of this work will be approved?

Softus · 12 Mar 2006

Gasguru said:
I was merely stating it is better to keep the BCO on your side.

Really? There appears to be a complete absence of such a statement in your previous post.

Gasguru said:
Or are you suggesting none of this work will be approved?

I can hardly believe that you're asking that, but, for the record, no - I am not suggesting that none of it will be approved.

As for the rest of your vague nonsense, I can't be a*rsed to argue about it (for once) - I must be getting old.

Gasguru · 12 Mar 2006

What vaque nonsense, wouild that be?

What do you know, you have to look it up basic plumbing knowledge but then you are old.

Softus · 12 Mar 2006

Gasguru said:
...you have to look it up basic plumbing knowledge...

I don't keep every fact in the plumbing universe inside my head. When I believe something, but need to check my facts, I look it up. IMHO it's far more important to know that there is a rule, and to know where to find it, than to know every rule at every moment. Frankly, whilst I make all types of connections most days of the week, very few of these are onto a soil stack.

From your unsuccessful attempt to belittle me I assume that you never look anything up, which might explain an awful lot about the 'facts' that you present.

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New bathroom drainage

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