2015, Forester MBS - Fresh Water Tank

[FIVE2MH]

We have been camping a week in June Lake, CA - full hook ups. When we arrived, we had 2/3 fresh water in the tank. When we prepared to depart this morning, the fresh water tank was full and water was dribbling out the fill cap. We did not fill the tank at anytime during the week, as we were using city water. Does anyone know why our tank filled up?
Thank you!

[DaveJordan]

Well... I don't KNOW what happened, but I can guess...

The fresh water system is designed to take water either from the city water inlet or from the tank, via the water pump. Those two sources have to connect somewhere before entering the main MH plumbing.

To avoid the problem you seem to have, two back flow preventers are needed - one on each of the two input lines. I don't know where these are - perhaps one is built in to the water pump? - but the one on the tank/water pump line is at least partially open, allowing the city water to flow backwards through the pump and into the tank.

Since water isn't gushing out of the gravity fill, I'd guess that the opening is fairly small - maybe something is caught it in, preventing it from closing completely. One thought - you might run the pump, forcing water through that path, which might clear an obstruction.

Anyway, all of this is speculation on my part....

Dave

[DaveJordan]

This thread talks about plumbing modifications:
http://www.forestriverforums.com/for...ion-59388.html

The diagram shows two check valves - after the city water inlet, and after the water pump. It also suggests a possible (short term) workaround for you ... When using city water, put your "winterize" valve in the winterize position - then maybe the water will drain to the ground rather than filling your tank...

Dave

[FIVE2MH]

Thanks so much, Dave. Good information - we'll check it out!!

[TARVIDSON]

On some other post I was reading that the leaking back into the fresh water tank can be caused by having the water pump turned on and being hooked up at the same time. It was also mentioned that it can sometimes be cured by(if I remember this right) opening a faucet and running your pump with city water unhooked. Don't know if that applied to your case, they also mentioned that changing a backflow valve is not that hard and available at RV stores. Good luck on fixing that.

[FIVE2MH]

That could be the case, Tarvidson?? We moved to another campground, didn't turn on the water pump and the tank didn't fill up.
Thanks for responding!
LOVE this forum!

[TARVIDSON]

I hope that was all the problem was. I absolutely agree about the forum. I have learned more about RV's in general in one year than I would have in ten without it!
Happy travels,
Tarvidson