2012 Cyclone HD 3612 shower and bath sink drain slow

[Old-Sparky]

I recently purchased a 2012 Cyclone HD 3612. When using either the bathroom sink or the shower, I find that the drains for both are slow to drain. I removed the p-trap under the sink, but it was clear. Both grey tanks and the black tank were empty. Tank levels do not change the slow drains any. Kitchen drain works very well. Any tips on how to find the cause of the slow drains? Thanks.

 

[hoefler]

Check the tank vent, if blocked, drains will be slow. Open the dump valve, and see if the drains improve.

 

[Old-Sparky]

It has an AAV under the bathroom sink. I will have to remove it and see if it helps it drain. I will have to wait until we are camping somewhere to try leaving the dump valve open.
Thanks.