2008 CS city water overflowing fresh water tank.

Sam452

This is a first for me. I had thought that the city water and freshwater container were separate systems. When we purchased this used and hooked city water to the T@B it never filled up the fresh water container. On the times when we didn't hook up city water, we used the pump to draw water from the container. 

I see that the pump appears to be the meeting point for city water and container water. Either my pump has gone bad or something has changed. 
Now when I turn on city water, I find my freshwater container are overflowing which never happened before. If it did, that bottom would have rotted out years ago. 
Full disclosure, I used my pump to draw water from the container when I foolishly did not use the pressure regulator from the city water spigot into my T@B which blew out the poly pipes under the sink. Now that I have the pipes Hooked back up again, I'm using city water again. Except when I don't need it. 
Am I misunderstanding how this system is supposed to work? 

Pardon if this was easily searchable, but it didn't come up for me.
Sam

rfuss928

There is a check valve in the pump to prevent the backflow you describe.  It is possible the high pressure event you describe has caused the valve to stick.

Sam452

Thank you. This pump is a ShurFlo 105-003. In searching for this valve, is this check valve internal to the pump,  or external in the pipe from the pump? Not clear yet. 

pthomas745

There are a lot of posts on pump repair.  The check valve is part of the pump.  Look over this thread.

https://tab-rv.vanillacommunity.com/discussion/6570/water-pump-not-pumping

This is a video about it.  Not sure if it exactly pertains to your pump, however.

https://www.youtube.com/watch?v=SKvzYoTs4J0

This appears to be a repair manual for that version of pump.

https://www.pentair.com/content/dam/extranet/web/nam/shurflo/manuals/911-585-lo-flo-105-series-rv-pumps-iom.pdf

Sam452

Thank you, this is very helpful. The link for my pump prompted my question as its diagram indicated the check valve was external. I believe I have another problem with this pump and I'll disassemble it soon to investigate it further.