Replace them with something else, like the newer style vane pumps. I had them in the Formula (3 bilge pumps), went through several sets while I owned it, new ones would die after less than a year. They are made by ITT Jabsco and I sent them the defective ones but never got a reply. You really don't need them for a fresh water system, as their main (only?) virture is if you need to mount the pumps above the water intakes.