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Height of an Air Admittance Valve in a bathroom

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Paul Cockhill

Hi Everyone

I am fitting an air admittance valve to a stack pipe in a bathroom, see pictures. A separate washbasin waste pipe and bath waste pipe are also connecting to the soil pipe.

I have fitted an anti syphon trap to the washbasin and a HepVo to the bath

My question is
Is there a minimum height the AAV has to be in the bathroom?

My clients want it as low as possible and boxed in. I know once it is boxed in there will have to be an air grill

Any advice greatly appreciated

Best wishes

Paul

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An air admittance valve is just that, it admits air, it isn't supposed to let air or water out. Now occasionally they do fail/stick and let sewer gas out or if you have a clog will leak some. Personally I don't like them and I rarely see an instance where you couldn't have just run a proper vent pipe. That said they do serve an important purpose and can help waste drain more properly.

Generally when we fit them they go under a sink in the back of the cabinet as high as possible. Technically they should be above the flood rim of the highest appliance which is almost always a sink/basin.

I snake drains as my primary function. I have seen enough clogs in vertical 100mm/4" pipe to know that they can happen and it's always been old rusty cast iron pipe. They only time I like AAV's is when I can unscrew them and use them for a snaking point. Often I put a glove around them and vacuum out the clog. In that case a regular vent would be worse for me but I can't help but think that the drain wouldn't have clogged in the first place if it was properly vented.
 
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Paul Cockhill said:
Hi Everyone

I am fitting an air admittance valve to a stack pipe in a bathroom, see pictures. A separate washbasin waste pipe and bath waste pipe are also connecting to the soil pipe.

I have fitted an anti syphon trap to the washbasin and a HepVo to the bath

My question is
Is there a minimum height the AAV has to be in the bathroom?

My clients want it as low as possible and boxed in. I know once it is boxed in there will have to be an air grill

Any advice greatly appreciated

Best wishes

Paul

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The Floplast AV110G Air Admittance Valves can be fitted below the flood level of the highest appliance. These valves are very good and I've not had one single problem with them, and even have one fitted in my own house. It's a good space saver as it's fitted inside the cabinet for a back to the wall loo and eliminates the boxed in stack going up the wall.
Make sure that air is allowed to circulate near these valves though or they won't work. Fitting a small vent grille is fine if boxing it in.
 
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