We just had a sub pump installed in our basement to to remove water from a washer. We did not have sewer line below our basement and must pump water up to meet the sewer line that runs down the back of the house. The problem is that when we tested the pump, suds overflowed from the pump onto the floor even when using the smallest amount of detergent. Also, we are unable to go beyond a medium load due to the issue with the suds. Does anyone have any suggestions as to what the problem might be. The plumber says that he never encountered this and regularly installs them.

Is this just an open pit for the sump? It should be covered/sealed and vented.

Sub pump! I'm assuming you don't mean a sump pump with a open pit. Would this be a pump connected on to the washer hose acting as a booster pump? Please explain ,in detail, exactly what your set up is. Regards, Tom