Hi-I had a powder room installed in an addition w a toilet w an injector pump. Initially it caused backflow into basement sink. A plumber added a check valve under bsmt sink and corrected this problem. But secondary issue is that when flushed a few times the Kitchen sink-located on main floor as is toilet w injector pump-will gurgle.
Is this a problem I should be concerned with and if so how can it be corrected- help as I am selling my home and do not want to pass on any possible issues to new buyer-