Tricky plumbing question: Air admittance valves – 1 1/4"

Ive got a bit of a problem with syphoning of the low profile shower trap when draining other appliances on the same run.

The shower trap is at the end of the run, two basins come next (in a single pipe), then bath, and that lot all joins into the soil stack at about the same level that the WC pan joins the stack. Top of stack has an AAV.

Basin draining seems to be sucking at the shower trap. I can fit a small AAV to the basin waste run, after the two basin traps, but before it joins the main run under the floorboards. Would this work?

it will help but may not entirely cure the issue

will have a go at it.
Just filling a trolley with an AAV and loads of goodies at screwfix now.

Small diameter AAVs were much cheaper at Toolstation last time I bought some…

cheers -m-

they have the mcalpine one on the integrated T that I was after too.

Couldnt find it anywhere but the mcalpine site.

Make sure your existing aav has a good supply of air. You would’nt believe the amount of plumbers who think its ok to stick an aav into a partition (that gets sealed up with plaster etc).

do you know what size pipe they are connected to under the floor? basins, bath and shower on one pipe should be connected to a 2″ pipe minimum before going to the stack.

you could try one of these as the shower trap

http://www.plumbingpages.com/featurepages/SHepvo.cfm

put it in line and no need for a water seal

watch this for proof they work

Yup, try the hep v o if it doesn’t work.