Waste Pipe Diameter

[pertinky]

Hey guys,

I've got an existing branch using 50mm waste pipe running externally in to the stack and reducing to 40/40/32 inside for shower/bath/basin

I'm moving the basin which basically means I'm replacing the entire branch as the basin is going to sit another 1.2m further away from the stack and come through the wall a couple of inches lower than the existing branch. The old branch will drop in to the new branch with a tee.

Am I OK to replace the 50mm pipe with 40mm? Seems its not quite common these days (this would be circa 2000)

 

[muggles]

No, you should retain the 50mm, and also consider upgrading your basin waste to 40mm for that length of run - max run of 32mm according to Building Regs is 1.7 metres

 

[pertinky]

No, you should retain the 50mm, and also consider upgrading your basin waste to 40mm for that length of run - max run of 32mm according to Building Regs is 1.7 metres

Thanks for the heads up!

Do you have a link to the regs? I'll familiarise myself with them.

Annoyingly Screwfix doesnt stock alot of 50mm pipe fittings so will have to look elsewhere.

 

[muggles]

Part H is what you need

All major plumbers merchants will carry 50mm on the shelf

 

[pertinky]

Looks like I'll need to install AAV as well then as the new basin location means a run down the joist of 2.5m, then a run of 3m (externally) back to the stack

 

[pertinky]

@muggles

So I'd be looking at:

Basin - 40mm + AAV + 2.5m run to outside where it will increase to 50mm (3m run to stack)
Shower - 40mm + 2m run to Tee (bath) + 0.2m run to outside where it will increase to 50mm and join basin branch (1.8m run to stack)
Bath - 40mm + 1m run to Tee (shower) + 0.2m run to outside where it will increase to 50mm and join basin branch (1.8m run to stack)

Does this sound OK?

The location of the bath/shower hasnt changed, and since we've been here I've not had any issues with siphoning. The basin has basically moved to the opposite corner of the room so its got the extra 2.5m on it going across the room.

The ensuite is going to have its own branch when I get around to doing it

 

[Hugh Jaleak]

I'd be very cautious about putting a bath and shower on the same waste run, personally I'd do them separately if you can. Not unknown for the waste to block over time, someone to release a full bath of water, and it remerge in the shower. Went to one where this had happened, by time the Lass had realised, she'd got water dripping through her kitchen ceiling.

 

[pertinky]

I'd be very cautious about putting a bath and shower on the same waste run, personally I'd do them separately if you can. Not unknown for the waste to block over time, someone to release a full bath of water, and it remerge in the shower. Went to one where this had happened, by time the Lass had realised, she'd got water dripping through her kitchen ceiling.

Unfortunately the waste runs through the webbing of an RSJ so no real option here to run a separate branch other than to make sure its 50mm up to the Tee for the bath/shower .

 

[durhamplumber]

https://www.google.co.uk/url?sa=t&s...FjAJegQIAxAB&usg=AOvVaw1RPo2slDWgPR_8Pfv2seMP
Page 5

 

[pertinky]

@durhamplumber thanks

I've read it but I'm not finding it clear what happens > 4m run. 50mm waste? AAV? Or is it not recommended at all?

Want to be as compliant as possible but this is an old cottage... Some compromises have to be made I've got limited access and s really bad original first fix

 

[Hugh Jaleak]

Unfortunately the waste runs through the webbing of an RSJ so no real option here to run a separate branch other than to make sure its 50mm up to the Tee for the bath/shower .

Fair comment. Advise then you make sure it's accessible for cleaning as required.