After the first use since winterizing, my water pump cycles on and off. The check valve was acting up also, allowing city water to fill the fresh water tank. I took the pump apart and think I fixed that. But the pump still cycles, and when it shuts off, there is definitely a hissing sound. No water comes out anywhere. I definitely feel like it should not make that sound, but maybe they do right after shutting down...? I can't figure out where else there might be a leak in the system. I ran a ton of antifreeze through the pump and pipes, so I feel confident there isn't a busted pipe anywhere. Is it likely just a pump needing replaced? I've check the input/output hoses and the o-rings look fine..... Rig is only a year old.