Is this all legal??

[dthomas2]

Originally Posted by twasion

That may depend on where you are located and which plumbing code you are under. If I had done this in Iowa the plumbing inspector would have told me to do it correctly. Above the flood rim. This is done in case of backup.

While you may be right, I am certainly no expert, I have to wonder. If we think about the way the valve is constructed (if the manufacturer does not specifically state that the VVA must be above the flood rim) it is inherently a one way valve - either air or water is prevented from back flow. Then, even if we have a backup of the waist water, wouldn't it's placement above the flood rim make no difference? I don't doubt that some code would say that but it is pretty hard to believe that it would be necessary. Am I off base?

[jclark1]

It depends on what the purpose of the AAV is. For fixture venting it needs to be a certain distance above the weir of the trap. For stack venting it needs to be above the flood level of the highest fixture.
And it's very doubtful that little sealing membrane would stop any kind of waste backup.

[twasion]

Though it’s technically a one way valve it’s still a mechanical valve and it may fail to hold water back as I’ve experienced. When they do leak and it is not above the flood rim it can be quit a mess and often times ends up in the basement if there is one.

[dthomas2]

Thanks guys. Good info.