Water Pump Won't Shut Off

[GeezerViz]

Thanks all for your help. Turns out that the outside shower was slightly on. As soon as tightened the cold water knob, water pump shut off.

[Steve 716]

Is your fresh water tank also filling when your pump is running? If so the cheapo plastic check valve in your pump has failed. The solution is to purchase a Shark Bite one way check valve from a hardware store (around $10), cut the output pex line coming from your water pump (make sure you cut it flat, not angled, and you leave enough pex to connect to the new check valve), push both ends of the cut pex line into the new valve, and you are done. Make sure the arrow on the Shark Bite points away from your water pump when you install it. The install will take you about ten minutes.

I still carry a spare water pump in its box that I purchased a few years ago before figuring out the check valve / water pump problem and installing my new check valve. I have given several RVers this fix and, to the best of my knowledge, none of us have had a problem since.