DIY Doctor

Main navigation

internal soil stack in bathroom

Postby wally » Fri Jun 01, 2007 10:29 am

We want to re-fit our bathroom with a new suite. The problem we have is that the soil stack runs up the corner of the bathroom wall (boarded in), and takes the soil pipe from the loo, plus the waste pipes from the bath and basin. (it also goes through the downstairs loo for that waste too) This projects into the bathroom by about a foot each way. If we could remove the upper part of the stack, leaving the lower part to take the loo waste, it would enable us to fit the basin and loo directly onto the wall and not have a boxed in effect. Our neighbours have done this to give themselves more space. My worry is. should the top of the soil stack should be vented somewhere ? I feel that by capping it off at bathroom floor level we might be causing problems in the future. i.e. smells ! What do you suggest ?
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Fri Jun 01, 2007 10:10 am


Simply Build It

Postby thedoctor » Mon Jun 04, 2007 9:29 am

You must not cap off the pipe at all, inside or out Wally. The reason that it goes to the roof is that it takes the foul (flammable & toxic) gasses to above window level to release them. If you cap it it can only build up and became dangerous. There may be a chance you can fit an air inlet valve to the pipe if its cut down to basin level. See our project on air inlet valves and check with a local plumber ( Most plumbers will give advice for an hour if you pay them) if its ok to install a valve in your bathroom. The valves are commonly called Dirgo valves and the sanitary arrangements must comply with certain regulations before you can fit them.
Posts: 2530
Joined: Sat Apr 08, 2006 12:15 pm

Postby tedbuilder » Wed Jan 07, 2009 8:09 am

hey there,
i am a builder and currently in war with the client about the venting of the soil stack.
i have cut off the vent that finished 2 foot above gutter line and constructed a loft conversion and put a dirgo valve inside the roof space but also higher than the highest trap that is in the house.
i was hoping you could shed some light on this topic for me please.
the house is a terreced house 4 in from the end. i have several plumbers and building control officers tell me its ok but the client is adamit that it is incorrect.
what are your thoughts?
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Wed Jan 07, 2009 7:52 am

Postby Steve the gas » Thu Jan 08, 2009 6:19 am

I reckon the AAV is ok. If BC say you can then thats that IMO.
Steve the gas
Rank: Site Agent
Progress to next rank:
Posts: 780
Joined: Sun May 04, 2008 7:07 am

Postby plumbbob » Thu Jan 08, 2009 5:13 pm

Tedbuilder I'm with Steve a dirgo is fine.

The whole point of a soil stack, AAV or Dirgo is to avoid a vacuum being created in the soil pipe by allowing outside air into the pipe without letting the odours out.

When the toilet is flushed the movement of water may cause a partial vacuum to form resulting in water being sucked out of any traps connected to the system breaking the water seal.
Rank: Project Manager
Posts: 1891
Joined: Wed May 07, 2008 9:59 pm

Postby Tuono » Wed Jul 08, 2009 8:15 am

I've a nieve soil stack question.

How far can a toilet waste pipe run horizontally? I'm fitting a new bathroom in my bungalow and the desired new toilet location is about a metre or so away from where the soil pipe goes through the floor. Would this be a problem :?:

Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Wed Jul 08, 2009 8:10 am

Postby plumbbob » Wed Jul 08, 2009 10:21 am

Well obviously, a soil pipe cannot run horizontally at all - it must have a fall. Providing the fall is sufficient, then it can run any distance "horizontally".

You will find your problem is when fitting a normal elbow to connect the horizontal pipe to the connection in the ground, it makes the pipe about an inch higher than the outlet of the toilet so waste water would have to run uphill to flow away.

The only way I have found around this problem is to fix a right angle pan connector into the ground then the horizontal pipe into that. Doing this will leave the pipe pretty much touching the floor at one end, and 4 inches or so higher the toilet end giving the fall you need.
Rank: Project Manager
Posts: 1891
Joined: Wed May 07, 2008 9:59 pm

Postby XDB » Mon Jul 13, 2009 8:31 pm

My 1970s detached bungalow doesn't have a soil/vent stack and no provision for one, my neighbour doesn't have one either. He has lived there since it was built and says no vent pipe was ever fitted. Is this right and what can I do about it. The toilet flushes vigorously.
Rank: Apprentice
Progress to next rank:
Posts: 8
Joined: Thu Mar 05, 2009 7:52 pm

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics