Air Admittance Valves

[gasbusters]

Never fit one before, but considering one for my loft conversion. How reliable are they? Are they any good? Screwfix has some FloMaster types ranging from £17 to £40. At the moment the soil stack terminates through the roof, but will be removing stack soon and was looking into one of these AAV.

 

[motorbiking]

If you don't fit one, how will you stop a vacuum sucking all the standing water out of your U bends?

 

[just pumps]

Leave it be and work around it, open vent is the best imho.

 

[Hugh Jaleak]

Could easily create more problems than you solve, replacing an open vent with an AAV is not recommended. Post the other day where the OP had done this and was having issues with odours in his bathroom, as positive pressure was looking for a route for escape, easiest option became the bathroom basin.

Keep the stack vented and work around it.

 

[gasbusters]

At the moment the soil pipe goes through roof. The AAV will be about 0.75 meters below the existing termination, just inside the roof, so not far from where it is now. Ive seen AAVs advertised a lot, surely they can't be that bad if so many use them?

 

[Hugh Jaleak]

AAV's do what they say on the tin, they admit air. What they dont do is let positive pressure out, so it doesn't matter where you site them, it still works the same. Drains need to breathe, hence why Building Regs state the drainage system must be ventilated, and Builders put at least one vent stack on each property. Seen numerous instances of AAV's being used to replace vented stacks, and then problems ensuing. See here: Foul smell in bathroom since Durgo valve installed | DIYnot Forums

My advice is based on years of experience in and around drains, but ultimately it's your call.

 

[gasbusters]

AAV's do what they say on the tin, they admit air. What they dont do is let positive pressure out, so it doesn't matter where you site them, it still works the same. Drains need to breathe, hence why Building Regs state the drainage system must be ventilated, and Builders put at least one vent stack on each property. Seen numerous instances of AAV's being used to replace vented stacks, and then problems ensuing. See here: Foul smell in bathroom since Durgo valve installed | DIYnot Forums

My advice is based on years of experience in and around drains, but ultimately it's your call.

So your saying these AAVs are pretty much not fit for purpose and will likely cause me a number of problems?

 

[Hugh Jaleak]

So your saying these AAVs are pretty much not fit for purpose and will likely cause me a number of problems?

No, I am saying they have their place, e.g. on a Ground floor stub stack setup, where the upper floor bathroom(s) may discharge into a vented stack. Provided there is at least one other vented stack on the property they can be used elsewhere.

What I am not advising is capping an existing vented stack with an AAV, as it could create other issues, e.g. those encountered in the other post I linked to above.