Should my bathroom waste be vented?

19 Dec 2012
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United Kingdom

I've got a recently built extension with a bathroom. The shower trap is letting sewerage smells come up from it. I've been doing a bit of research and I'm thinking that the issue may be that the soil stack is not vented. The waste from the shower, bath and basin connect to this stack on the outside wall. See photo attached.

Can anyone advise, should the soil pipe have been fitted with a vent at the top or is there ever a reason why a vent would not be fitted ?

If a vent is needed does it need to be added at the top of the soil pipe on the outside wall or would it be possible to fit and internal vent somehow?

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Yes it should be ventilated, unless you have another stack ventilating elsewhere? did building control pass it?

Where the elbow goes through the wall should be a branch connection and the vent connected to that. If it’s within 3m of a window it needs to go at least 900mm above the top of the window to prevent smells entering.
At a minimum it should have an Air Admittance Valve (AAV), on the stack, although ideally it should be vented to atmosphere. If your getting the builder back to sort it out, I'd insist it's vented correctly.

Difficult to say whether the issue is traps are being pulled, (allowing stale air back into the room), or if there's positive pressure in the system blowing back into the room. If positive pressure is the issue, fitting an AAV wont relieve it, and/or alleviate the problem, but then you need to see why positive pressure is building in the system...
Yes it should be ventilated, unless you have another stack ventilating elsewhere? did building control pass it?

We do actually have another stack from the en-suite and that one is ventilated. The 2 stacks are not connected but both feed into the same man hole.
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Is there anything else on the stack? Toilet?

The other thing I would mention is that if it's not an illusion of the picture then that left hand run doesn't have a fall on it, like the the right hand run does, in fact it actually looks like it's running uphill?
Yes there's a toilet on there and the 3 smaller pipes are bath, shower, basin.

I think that re. the fall on the pipe on the left, that is just due to the angle of the picture - it does have a fall on it

Yes it needs an open upstand on the stack. As it is, when the toilet is flushed, the rush of water down the stack sucks out the water from the shower trap ( probably a shallow trap). The trap is then open to sewer smells. You probably get gurggling sounds in the shower when you flush the toilet.
Ok thanks to all who have responded. Sounds like the stack should have been vented when it was installed so I'll go back to the builder on this and tell him it needs to have a vent fitted
Can you put another pic up of the rest of that wall above that point, and we'll tell you exactly what's needed, before he bodges anything else up. If they cant get a stack right, I have to wonder what else isn't right....
Looking at that pic again and following the brick line against the pipe then it isn't running properly, not like the pipe on the right. Can you give us a pic straight on?
It would of been so easy to do at the time of install I dont know why they wouldn't of done it.
In the meantime, keep a bucket or plastic jug to throw water down the shower waste after the toilet isflushed. This will refill the shower trap.
Nice back fall on the left hand connection. Get the builder to sort that out as well. The right hand connection is undersized, get some anti-vac traps to. You'll need them. Good old building control!

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