Do I need an AAV here?

[benaround3]

Hi

We have a small utility cupboard for a washing machine with a standard washing machine waste kit installed as shown. For complicated reasons we need to raise the floor as shown but this means we obviously need to raise the washing machine waste trap.

The shaded area is how the team of builders that built the bathroom section, which is an extension on a beam and block floor, left things. I am not precisely sure of the below ground arrangement but they did put in the soil stack as shown. There is a shower and w c not shown. The w. machine waste actually joins up with the shower waste before joining the soil pipe.

Then the plumber took over and installed the waste kit.

After researching this for issues of self siphoning etc before I raise the P trap it looks as though the installation is more of an S trap than a P trap due to the downward bend immediately after the P trap. In fact if I raise the P trap as I plan to, just by a few inches, there will be an additional step, I don't see any other way of doing it.

But in any case it seems to me there should be a local AAV just after the P trap. Is that correct? But I can't find any washing machine waste kits that incorporate one.

 

[Wayners]

I think its fine as is. If you were to get smells coming out washing machine waste then yeah, fit AAV. I don't think you will

 

[Hugh Jaleak]

No need for an AAV in that situation, and Washing Machine discharge needs to be open to atmosphere. Just be careful, if its connected to the shower downstream, and pipe gunges up over time, washing machine will continue to discharge, and if the water cannot get away quickly enough, it could back up out the shower and flood.