Help Help. I have a 17 foot
Boler, (1978 version) It has not been very well taken care of. When we drain the sink, we get water in the shower. I have 2 vents, one on the sink side and one comming out of the black waste tank. I have checked to make sure they are both clear. When I drain the sink, Water comes up in the shower. I am thinking that I need to put a vent into the grey water tank. I am thinking of putting a one way valve into the side of the tank at the top. Any thoughts. Yours in Bolering. Jim