Diameter Of Waste Pipe: What Size?

[securespark]

First post on plumbing guys!

I have searched here for tips about my problem.

I have a bathroom with basin & bath currently piped under the floor and out to a soil stack. Max length of pipe from sink to stack is circa 7m. The internal waste is all inch and a half.

They are piped individually inside the house, then join a piece of 38mm running to a stack.

Trouble is, the pipe connected to the stack is reduced to inch and a quarter, resulting in extremely slow emptying.

To cut a lot story short, I have to replace a flat roof through which the stack protrudes.

I therefore would like to rectify this pipework before the new roof goes on.

I realise I might need to replace part or all of the stack in doing this.

So, after all this waffle, my key questions are:

What diameter pipe is recommended to take away waste water from a bath and a sink into a 100mm soil stack?

Is 38mm still OK to run from the sink and bath to the outside?

I may add a shower basin in the bathroom. Whatever pipe diameter is chosen, I guess it would have to cope with waste from all three?

Thanks people!

 

[kevplumb]

use 50mm solvent weld

the stack will be 110

 

[securespark]

50mm enough for 3 possible outlets?

Fine. Thanks, Kev.

 

[kevplumb]

3 yup give my love to the wire twister

 

[kevplumb]

50mm enough for 3 possible outlets?

Fine. Thanks, Kev.

hit the button yer miserable git

jeez sparkys ony come second to joiners

 

[securespark]

I was going to, but I was waiting for your inevitable reply.

But now you've compared me to a chippie, you can kiss your thanks goodbye!

 

[kevplumb]

 

[securespark]

No, I have thanked you, honest guv!

I did consider grabbing it back, but thought better of it...

 

[securespark]

Forgive me for resurrecting this thread, but it is still ongoing.

I never had the pipe replaced as I could not get a plumber in before the new roof went on....

I am now in the long slow process of designing a new bathroom. Is 50mm still the way to go?

The reason I ask is that someone (a chippie as it happens) reckons inch and a quarter is OK as not everything will be draining to waste at the same time. However, I have my doubts, as I timed the bath emptying just now.

It will be replaced with an 1800 x 800, but the existing one is 1685 x 750mm. I cleared the waste with Sodium Hydroxide, then used a plunger (after blocking the overflow).

Then I filled it up to the overflow with water and pulled the plug. It took 5 mins 16 sec to empty.

Is that about right or is it slow? Maybe I'm impatient. Maybe it's a long time when you're standing there with a stopwatch, but it seemed slow to me.

Whaddya reckon guys? Replace with a 50mm pipe?

Thanks.

 

[Dan Robinson]

Way too long - upgrade the pipe.

 

[Hugh Jaleak]

Another issue could arise (if you haven't already fitted the shower), the discharge from the bath may not be able to get away quick enough, (or the pipe clogs up downstream before the stack), and you'll find the contents of the bath reappearing in the shower tray.

Looked at a job myself recently, young lady had a bath, pulled the plug and went to dry her hair. Came back to find the bath water had erupted out of the shower waste, flooding the bathroom, then began dripping through the kitchen ceiling below.

 

[plumbswe]

Google approved document H, sanitation. Longest run in 40mm allowed is (1"1/2) if I remember righlty is 3M. You need to make sure its on a gradient which is more pertinant than the bore of the pipe.

 

[securespark]

Way too long - upgrade the pipe.

I'll have a look at Doc H as Plumb says, but is 50mm the size to go for?

 

[Hugh Jaleak]

50mm is the biggest size waste pipe available, next up is 82mm soil. 50mm should handle 3 appliances, no problem.

 

[securespark]

Fantastic, thank you!