In my basement I have a pump in a sewage pit in the ground. I think the vent of this pit is somehow tied to the vent of a sink drain nearby.
The pump runs fine. But everytime when it shuts off after pumping out the waste, I hear a gurging sound out of the sink drain. And sometimes I can even see a little bit of water splashing out of the drain.
I suspect it is a venting problem but I can't open the wall now to see how they are tied together.
The sewage pump has a checkvalve directly above it. It seems that when it shuts off, the waste water falls back onto the checkvalue stop and creates some air pressure into the pit and push through the vent. But that's just my guess and even if it is true how can I fix it?