Wilko58

Hi Nick, Sadly no, it's all boxed in and in the bedroom on the other side of the bathroom wall so unless I rip it all out it isn't accessible. To be honest, I've left the new AAV in place even though it isn't readily accessible but it is now almost level with the basin trap. I've also changed the AAV in the attic although it's still 50mm. Many thanks for your and everyone else's help. I'll now close this so no need to reply. Cheers

The 110mm stack only goes downwards from 1st floor and is 50mm up to the attic where the (50mm) AAV is. I didn't realise that the AAV had to be accessible which means I can't have one at all in the bathroom - the stack is still boxed in and the WC frame is going to be boxed in as well and won't be able to be taken apart without taking the bowl off the wall. Do you think I should remove the AAV in the bathroom if it's not going to be accessible? I should add that the basin waste is one of the flap type so can't dry out as there is no water in it but in effect it should also work as an AAV given that air could be sucked through it. To be honest, I haven't checked the AAV in the attic as it isn't that easy to get too but I'll change it anyway. Once again many thanks.

I might be able to put the AAV above the trap height, depends on the space behind the WC Frame where it is going. The 50mm pipe drops down and then enters the stack below the floor level (I can't actually see it) and the WC 110mm pipe goes into stack and down a 110mm pipe but going upwards to the attic and AAV is a 50mm pipe. The AAV in the picture seems to rely on the weight of the valve to keep it shut so anything other than vertical could impede the operation.

Hi, Apologies once again for taking so long to reply. I've attached a pic of what I intend to do, the WC Stack has the pipe removed for clarity, the AAV for that is in the loft and only on 50mm pipe. Cheers

Thanks Nick. I can't get to where the 100mm changes to 50mm but I could add another using a branch but I do have room to add an AAV to the 50mm pipe after the bath and basin wastes if I can find the right fitting.

Thanks all. I'm installing a combined waste/bath filler which comes with an usual shaped built in trap but seems like it will work okay. Like @joe90 I don't use the bath that often and have an ensuite for showers so evaporation of the trap might also be an issue so I'll keep it topped up. I was going to fit the flap type waste to my basin which I guess will also serve as an AAV given that it could suck in air if it needed to or can/should I fit an AAV to the downpipe? Hopefully my last question on this so thanks so far.

Sorry all, I was caught up doing the preparation. I've uncovered more of the pipes and from what I can see, the main stack is 100mm pipe and appears to change to to 50mm in the loft space and is capped off with an AAV. the old bath waste was 40mm going into a T with a 32mm basin waste joining it and both going into a 50mm pipe - I thought hat joined the WC waste but it goes down into a void at the side of the 100mm pipe and I can't tell if it joins it further down or goes downstairs and outside separate from the 100mm pipe. I'm thinking of changing the AAV in the loft space (in case it isn't working) and add an AAV to the 50mm pipe - will that be a better solution? Thanks again

Hi, I've been in my house since 2006 (it was built in 2001) and I frequently get a bad smell coming from the bathroom which I believe is caused by flushing the toilet which seems to empty the trap on the bath. The bath waste is in 40mm which goes to a 40mm to 50mm with a swept bend to take the basin waste and then the 50mm disappears down a void at the side of the main stack (roof vented) but not sure if it is connected to the main stack lower down (it probably is hence when the toilet is flushed the waste causes a vacuum and empties the bath trap). Edit: I should have added that running the bath tap and refilling the trap stops the smell! Anyway, my question is that as I seem to be having an issue with the bath trap emptying should I fit an AAV (on the 50mm pipe) while I'm doing the refurbishment (all pipes up to the stack being replaced)? Thanks in advance.