[prndl]

Replace the valve or just the seals, either way you are going to have to completely disassemble the valve and the extension for the cable to do it. Not fun. When I replaced my black tank valve I had to do both valves (black and gray) as they were joined to a single outlet pipe. After reinstalling and testing with clear water I had a leak and had to do it all over again to get it seated correctly. Carry on.