Thanks in advance, I am fairly new to the business and still straightening out some issues. All check valves have been changed in the attic but without consistency the high pressure rinse water tank level will rise and overflow at night and sometimes not the rinse tank.... last night the soap and wax tanks backed up. There is not a check valve on any of the three cat pumps that provide high pressure to the self serve bays and I am thinking that the water is backing thru the cat pump and being forced into these tanks. It is not the hydrominder valves in the tanks...So do you think I am right???? Would appreciate your thoughts...