I have a basement bathroom with a sanitary pump to pump to an overhead drain line that was installed some time ago. It works well.
I now want to install an upstairs clothes washer that will drain into this same drain line just downstream of where the sanitary pump discharges into. I am concernted that if the pump check valve failed, the drain water from the washer would backflow into the pump sump and overflow it. Is there anyway to prevent this or are there any code requirements on how this new washer drain can be connected to the drain line?