Vent Cap

[R-Villa]

Our sink and shower would back up, or at best drain very slow, and would not completely empty when dumping gray water. 
We knew the previous owner had some roof repair that included a new vent cap. So, we took the cap off expecting to find a bird or wasp nest or something blocking and causing an air lock. 
We used a shop vac and was surprised when we removed a half gallon of water.  
Problem solved. Between the time the cap and been damaged and replaced, the uncovered vent must have experienced a rain storm. Hull 803.