impossible = possible

[downlocked]

Hi folks. I spotted water coming out of my fresh water tank overflow tube of my 2014 378TS. I am and have been parked in an rv park for months.
I have my city water line hooked up and hasn't been moved for weeks.
Since I'm not filling the fresh water tank the only logical thing for me to do was to shut off the city water. I did and overflow stopped.
Although I always thought these were two separate systems which would make it impossible for this to happen, they must be joined somewhere! After the lines go up inside and in back of the water panel I can't see what happens.
Anyone else ever had this problem?

[caper]

The check valve at your pump is allowing the back flow. Turn off city water and try running water through the system with the water pump. There could be some dirt in the check valve not allowing it to close all the way. If this does not work time to change the check valve at the water pump.

[5picker]

In addition to the above...'some' units have a valve in the plumbing line that will actually allow you to fill the fresh water tank while connected to city water. You mentioned you've been at your spot a while so I suppose you know whether you have this in your particular unit and whether you've turned the said valve if so equipped. I've read where the o-ring on this valve can go bad and allow cross filling too.

Most likely though, the check valve in the pump has debris stuck in it.

[downlocked]

Hi folks. Thanks, that's what it must have been. Turned off city water and used pump for the night. I switched back and all is well.

[5picker]

Glad you figured it out and thanks for posting back what the cure was.
Most folks don't do this and we never know.

[Iggy]

This sometimes happens when the city water pressure get high or when you accidently turn on your pump while hooked up to city water and when you turn off the pump the water tank slowly fills over a day or so. This has happened to me a few times and drove me crazy. I key factor was to insure when you hook up to city water you have no pressure in the system and I usually open the sink faucet and relieve any pressure so when I turn on city water the check valve wherever it is will only get the pressure from the street water.


This is just one idea that many people will encounter and it part of the learning curve when you have a motorhome.

[LittlePM]

We had the same problem, we couldn't figure out why our fresh water tank was full. So we do use the water regulator and check the tank often.

[Teamfour]

If you rarely use the fresh water tank, do what I did and install a cutoff valve on the outlet from the water pump. I will never worry about another stuck check valve again. If I need to use the pump for water or winterizing, I can simply open the valve.

[downlocked]

thanks, folks.
I will be putting in cutoff valve, Teamfour...great idea. LittlePM, I do have a water regulator but it's the adjustable kind and I now have it at 50#...prob should put other 40# standard one back on.
Thanks for the suggestion, Iggy. I'll put that on the checklist.