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Old 03-29-2021, 05:48 AM   #1
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Join Date: Dec 2016
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water overflow

While on city water my fresh water tank also fills up and overflows. While on city water I do not want water going into the fresh water tank. Any ideas what the issue might be and what I might do.
Thank you
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Old 03-29-2021, 07:30 AM   #2
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Not sure what equipment you have since it isn't in your profile or signature block. That said, when this happened to us it was a failed check-valve in the demand pump. If that check-valve fails, city water will flow backwards through the demand pump into your fresh water tank....
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Old 03-29-2021, 07:37 AM   #3
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The answer will often depend on what RV you have.
2015 Winnebago Vista 31KE on 2014 chassis
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Old 03-29-2021, 02:29 PM   #4
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likely your on/off faucet is leaking, either freezing ice messed it up or maybe a washer is bad, repair or replace it.
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Old 03-29-2021, 03:09 PM   #5
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Most common culprit is the simple check valve on the water inlet side of your water pump.

It can be a failed check valve or simply a little bit of dirt/grit in there. They are easy to clean, easy to replace and you may not need to do anything more than turn off the city water and live off of all that water in your tank using the pump for a few days.

When you’ve used up most of the water in the fresh tank turn the pump off and turn the city water back on. If it doesn’t happen again you’re probably good, for a while at least. If it does refill the tank you probably will need to replace it.

Some folks just buy a small cheap plastic check valve and install it in front of the water pump then it doesn’t matter if the built in check valve fails again.

None of us know what RV or water pump you have as you’ve not mentioned this info. But here’s a link to the common Shureflo water pump in many Winnebago RV:
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Old 04-07-2021, 04:08 PM   #6
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Manual Valve

Our 2001 Winnebago Journey has a manual valve that requires 1/4 twist one way or the other to switch back and forth for filling the fresh water tank or using city water. It is in the same compartment as the fresh water hose fittings and wastewater tank valves.
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Old 04-07-2021, 04:14 PM   #7
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I have had this problem on ours. I solved this issue by disconnecting from the spigot and running the water pump for a short time. I donít know why but this seems to help.
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Old 04-07-2021, 06:20 PM   #8
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On the older coaches there is a manual city fill valve that needs to be turned off after filling the fresh water tanks. Often this valve is left on fill or accidentally bumped over to the city fill position and overlooked.

Year and model of the coach would indeed be helpful since we could look up the Operators Manual specific to your coach which is available on Winnebago's web site.
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Old 04-07-2021, 06:32 PM   #9
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I have had this problem with the last 2 Winebagos. I was told it was due to a check valve in the water pump. Sureflow sent a rebuilt kit which didn't help. Then a new pump . that didn't help either. I cut the line and put a brass ball valve in the line ahead of the pump. That cured the problem but you need to open the valve to use the fresh water holding tank. I also had to use 2 clamps on each side of the valve to get it to seal am
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Old 04-07-2021, 07:23 PM   #10
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Same problem with our new 2020 Adventurer. Dealer changed the water pump and problem solved
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Old 04-07-2021, 07:36 PM   #11
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The water pumps on RV’s are cheap the check valves fail all the time. Sometimes if you run the pump the out flowing water will get the check valve to work, at least temporarily. I installed a a Flair-it shut of valve in the water line for the pump. Turn the valve to block water at the pump when on city water. Remember to switch valve when you go back to the pump. I carry an extra pump in case it fails but if you replace every pump that has a check valve fail you could be pretty busy. Same reason I carry and extra water valve for my toilet. Two important items on our rigs. Your situation may be different. The way you elect to solve this problem will be what you decide to do. Good luck.
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