Hi, bought an air admittance valve from Toolstation (item 77893 from toolstation.com) to avoid piercing the roof with my soil stack. It slides over the 110mm pipe quite snuggly but there is no rubber seal etc. Is this meant to be solvent welded or sealed with silicone? All the rest of the 110 mm soil from toolstation is push-fit and I was asssuming this would also be push-fit. Thank you
The ones I've seen have had a sort of corrugated rubber seal to the soil pipe. Could it be that it has a bit missing?
Personally I wouldn't want to use solvent as it will be impossible to ever remove. And from what others say on this group, that does occasionally happen. Silicone would work OK I would think though.
Jon.
I thought soil pipes had to vent to the outside?
Presumably this will vent into the roof space?
If this is correct, I can save myself a lot of money. :)
Mostly they do have to vent to the outside, but in some circs you can use an AAV instead.
However, having had a situation where some kind person put about 10Lb of rotting meat in our local drain, the smell of which came up through the anti syphon traps in our kitchen (as it was unable to get up the soil stack due to this having an AAV on top of it) I wouldn't recommend it.
We have now had the stack vented properly above the eaves.
Not so simple.
Air admittance valves are permitted in many but not all designs of soil stack.
It depends how you define 'vent'. It is a one-way valve which lets air in to stop a depression from forming in the stack but stops air - and hopefully smells! - from coming out.
AAVs are useful in some circumstances (I have one in my extension) but there are regs about having to have a 'properly' vented stack fairly close.
Hi, thank you for the reply. The AAV fits snugly over the 100mm pipe so no, there is no rubber seal missing
Yes, but. The stack furthest upstream must still vent to open air.
Other stacks can use the AAV provided it's 1m above the WC connection and inside (so it doesn't freeze stuck).
Not quite true. There has to be at least one vent every so often to prevent positive pressure, but it needn't be the most upstream one.
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