Air admittance valve problems...

[browny7]

Hi all,

I am currently experiencing problems with a slow draining sink. The sink is not blocked and pipework not blocked. I therefore fitted a trap with an AAV, the water still drains slowly, yet when i manually press the AAV the water quickly drains...but spills out of the valve.

I then decided to add an AAV to the pipework using a 1 1/2" tee with AAV. When i fit this vertically on the pipework it drained superbly...yet water spilled from the valve. I then rejigged the pipework and put the valve horizontally, then the water drained slowly again (but did not spill)...aaaaargh.

Is it possible to place the AAV in a position where it will allow air into the pipework to allow fast drainage of water without water spilling from the valve? I currently cant find any way or any correct position.

I can see the light at the end of the tunnel...yet I cant just quite reach it!!

Many thanks.

 

[Bernie2]

The AAV has got to be above the spill over level or lip of the washbasin.

Looks orrible mind.

Anyway by the sound of it, it might be as well to check for drain backpressure. Is the overall drainage system through vented?

 

[tsta]

Didn't think you could install an AAV horizontally? And does it not have to be 300mm above the spill level?

 

[browny7]

I don't think the whole system is vented, although not too sure. So the AAV has to be positioned above the sink? or above the level of the trap?

 

[tsta]

above the sink

 

[Bernie2]

Hmm!

Above the sink, when its below a full sink and you let the water out, then push the valve up water will come out. And yes they do have to be vertical.

If the sink waste discharges into a single stack system with a vent pipe going out the roof then the system is already through vented.

An anti vac trap will discharge water if you press the valve while its discharging. It's after the water has gone down the pipe that it opens if there is any vacuum behind the water.

A resealing trap does the same job but doesn't have a valve.

Once again the valve has got to be vertical.

But if you can't get the water to run out with the anti vac trap fitted, then there must be some other reason its not getting away. If the pipes are clear as you say and it has a reasonable fall on it, and it looks okay, that virtually just leaves back pressure to be considered and you can't put an open vent inside a house.

Hope this helps!