i think I know what the problem is, but will take any help I can get. When loving wife does the dishes, I have to go into the aft bathroom under sink and remove the check valve to relieve the tank pressure for the water in the kitchen sink to drain. We have had this unit for a whopping 2 months, new to us but we are the 2nd owner. I believe the vent pipe for the gray water is plugged. Any suggestions?