bath wastes sizes - Plumbing Forum | Plumbers Forums

kwlondon · 03-04-2008

Can anyone tell me what is the max length of a 40mm bath waste running into a 110mm stack before I have to up-size to 50mm?

KW London

wiggikins · 03-04-2008

On a single stack max length of 40mm should be no more than 3m

kwlondon · 04-04-2008

Thanks guys, wastes are just on 3m so we should be inside tolerances.

dleader · 06-04-2008

The answer that it doesn't matter is wrong!!!! The limit is 3.0m beyond this (or if you have problems) you should consider installing some method of ventilating the pipe IE running an additional pipe to allow air into the system to prevent the foramtion of a vacuum in the pipe as water flows through it or putting an air admittance valve in the system. With 50mm pipe you only allowing an additional 1m (limit 4m).

**ProffesorPlumb** · 10-04-2008

Thanks for that dleader

wigz · 03-09-2008

hi was just wondering even if the nearest stack was say 5 metres away and 4 being longest point for the waste on the bath (when upped to 50mm pipe). what is the solution
a whole new stack ?

madderose · 06-09-2008

tees with 1/1/2 durgos in line to entrain air into the run. We did a very large house that had a ring beam plate steel grid on top floor so all wastes had to been run above the floor and the architects decided they didnt want to see soilpipes on the front of building. Same silly twats or won designer of the year on C4 Grand designs by the way. We had 50mm runs in excess of 7 mtrs and all worked fine.

CharterGAS · 07-09-2008

if you cant get you r tolerances on a single stack system then you need to adjust to single stack modified!
The problem i see with durgos (although i do use them when i have to ) is that not inly do you need air to enter the system but also exit!! a durgo has non return so how can air escape if need be to give an equal positive nad negative pressure in the pipe work??
I can t see the main stack vent doing this as although it is 4" to the termination its axillary purpose is to vent the manhole hence such a large termination. Most fixture unit rating on a domestic property could really se you use a 50mm stack vent but venting the manhole prevents this!