Shower on shore, overflowed Fresh tank

[hbillsmith]

This is weird and I suspect some sort of check valve. If you've got the time, take a read on this way too long message and chime in if you have thoughts on a resolution.

While hooked up to city water (with a pressure regulator holding input at 40psi) I was showering when the camp manager knocked on the door to tell me he saw water coming out of my connections enclosure. I went out (dressed first heehee) and opened the door to find water dribbling out of the fresh water tank fill's vent opening. I removed the fresh water fill cap and water gushed out. Apparently, my fresh water tank filled completely and overflowed thru the vent. I opened the low point drain for that tank, let it empty completely and verified its emptiness at the sensor panel. For now I can just keep an eye on it until its repaired.

I think this must be a pressure valve or water pump issue. To me it seems like the city water lines are backfilling thru either the pump or that valve that is used to tell the trailer the difference when I'm on City Water vs. Fresh tank.

Additional notes: 1) My unit does NOT have a manual valve I must switch over. I have a valve to suck in anti-freeze and a valve to by-pass the HW heater for winterizing. Both are set in the normal, non-winter positions. 2) I've gone back and forth from dry camping to city water camping several times and never had this issue before. 3) I usually carry about 5 gals in the fresh tank when traveling (toilet flush) and the pump has been working just fine, this is my first time to overflow fresh tank.

I don't have any damage from the overflow and everything is dry and not leaking anymore as long as I watch my sensors and don't let the fresh tank overfill (50gals). Other that just wasting water, for now its merely a nuisance. Thanks for taking a look.

[youroo]

Check valve in water pump! Unhook City water run on pump for a while,if still filling after you hook back up to city water and turn off pump,you need to repair/replace pump! Youroo!!

[Teamfour]

Youroo is correct. However, I tried what he says (running on pump for a while), and even took the pump apart and cleaned the check valve. Nothing worked. So I put a shutoff valve in the line between the pump outlet and the cold water line. Now I just open the valve in the rare case that we use the fresh water tank and the pump or when winterizing.

[hbillsmith]

I had a feeling this site would have the answer. I'll try the youroo fix first and then I'll do what teamfour is recommending. It's easy to get to the pump and adding a cutoff will be mucho simple.

Thanks to both of you.

[Rich5117]

X2 on the previous posts, you would be surprised how many times this happens. Shur flow makes a separate inline check valve if you would rather not have to open a valve, cost is around 12 bucks.