Air Admittance Valve Issue

[NickH284]

Sorry if this has already been answered, I searched but didn’t find exactly this subject. There’s an intermittent sewage smell from the back to wall toilet unit.
Is it likely this is a faulty air admit valve? It looks like it’s probably a McAlpine style one.
Is swapping this a good place to start?
I see some have different Ltr/sec flow rates, how do I know which I need?
And last Q, is the swap process straightforward or is there anything I need to be aware of so I don’t get showered in s**t

Thanks in advance!

 

[polesapart]

Looks to me like the AAV is of the type sized to fit into plain pipe not a (wider) socket.

 

[HERTS P&D]

Here you go:

McAlpine Push-Fit Air Admittance Valve Grey 75/110mm - Screwfix

Order online at Screwfix.com. For use in above ground drainage systems. Provides ventilation under conditions of reduced pressure when ventilating pipes are terminated inside buildings. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Andy

 

[Hugh Jaleak]

Before condemning the AAV, I'd refit it correctly, and see if that solves your issue. Polesapart has already picked up on the fact it's the type that needs fitting into a spigot end, not a socket, so it's quite possible it's not an airtight fit currently so is allowing odour to escape into the room. However, it looks like it's been sited a bit too low down on the system, AAV's should be fitted above the spillover level of the highest appliance connected to the stack, either the WC or basin, (if fitted), so ideally it needs to come up a bit.

If room is available to raise the stack up a bit to clear the WC/basin height, then remove the AAV, then find yourself a piece of 110mm plastic pipe of a suitable length. (Note, one end must be chamfered to go into the socket.) Smear of soap or Fairy liquid on the chamfered end, and gently push it home into the socket, slightly twisting it may help it drop in. Replace AAV in top of the pipe and see how you get on.