Last fall I had a sand filter replaced with a cartridge filter. Immediately after the filter was replaced the spa water level drops slowly after the pump is turned off. It drops several inches to where plaster is exposed.
I have had Leslie's out twice (as they replaced the filter) and the second time they recommended replacing the check valves which I approved. They installed the valves yet I still have the problem. Any ideas?
FYI I don't use the chlorinator