Hi, I am installing a new en-suite toilet upstairs in a new location , the soil stack is installed by my builder going downstairs directly and into the ground where the main sewers are. He’s installed the air admittance valve on the floor below , which is slightly below where the toilet is. I asked the plumber if it’s ok as it’s below the toilet , he said yes, but most places I read online saying it needs to be above a certain level. Can anyone help me please , as the plumbers insisted it’s ok.
It needs to be above the highest spill over point of the sanitaryware that drains into the pipe - so either above the rim of the toilet pan or if a basin also drains into it then it must go above height of the top of the basin. Unless regs have changed recently that is!
Mcalpine ventapipe AAVs are able to be fitted above or below the spill level https://mcalpineplumbing.com/sites/default/files/section_6.pdf
Thanks , I understand the regs require this , obviously my builders are not following it , and unwilling to do it another way coz it requires more work my concern is whether if the physics will work , that is the valve installed below the toilet level , it’s in the garage , which the soil pipe runs to the ground. Will it cause smell to be released or blockages ? thanks
I think the only reason for the height requirement is so that in the event of a blockage, any overflow would be highly evident by running into a basin/toilet etc. If an AAV is below the spill level, then an overflow could result in a leak from the valve first, which if boxed in will not be seen, and likely to cause a lot of damage. I assume AAVs that can be fitted at any level won't leak.