Intermittent AAV Draining Issue

[Sdiver2489]

I've read a few of the AAV posts on here and I'm trying to piece together all the information for my situation.

I have two sinks on a branch...the sink closest to the AAV drains slowly...sometimes and only backs up after the water is left on for a decent time (like shaving). I have not been able to get the sink further from the AAV to back up.

I've read about positive pressure being created and locking the AAV down. I did try to snake the drain from the AAV location and didn't find anything for the amount of snake I could feed. The house is relatively new (12 years).

I replaced the AAV and initially thought that fixed the issue as I left the water running and it wasn't backing up and draining fast.

This morning I was shaving and sure enough the water started to back up again. I unscrewed the AAV just a little bit and the sink immediately drained. It then kept draining nicely. I then screwed the AAV back on, and this is where I'm confused, when it likely sealed again, it drained the toilet suddenly.

The toilet is on a different branch off the main stack and I believe it has a vent that goes right up to the roof. Is it possible this indicates a blocked roof vent?

 

[WorthFlorida]

You have blockage further down and the waste water is backing up. It's not the AAV. It should be above the flood level of the sink or as high as it can be under the sink. If you block off the AAV, the sink will fill up.

 

[Sponsor]

 

[Jeff H Young]

blocking a AAV wont cause a sink not to drain but it will likely suck the water out the trap