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Old 04-28-2017, 07:26 PM   #1
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City water filling fresh water tank

I have been on the road for the last three weeks in my one year old Flagstaff. During this time I have used city water connections on my 2-4 night stays. This morning I noticed that water was flowing from the freshwater tank fill inlet. Upon checking the freshwater tank the gauges registered full. I emptied that tank a month ago when de-winterizing the camper and haven't had any reason to check that tank level since so I don't know if the tank has been filling for three weeks or a couple of days. While it wasn't a heavy flow it was pretty steady.

The freshwater tank/pump combinations has been used less than three weeks total in the last year.

Any suggestions?

Thank you,


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Old 04-28-2017, 07:35 PM   #2
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Common issue... seems like it gets reported 3-5 times per month.
See these two threads (I used Search for "check valve"):

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Old 04-28-2017, 07:37 PM   #3
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The back flow valve in the pump is stuck.
Disconnect city water
Turn on a faucet and relieve pressure
Close faucet
Turn on water pump and allow water to run for about a minute
Close faucet.
once pump stops turn off pump
reconnect city water
You should be OK
If you run the water pump when connected to city water it can cause the valve to reseat improperly.

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Old 04-28-2017, 07:55 PM   #4
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Thank you!!!

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Old 04-29-2017, 12:56 PM   #5
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Water backup

You probably have a Shurflo 4008 Revolution water pump. It has a built in back flow with a valve to keep the pressure from fluctuating. You might be able to stop it by adjusting the cutoff on the bypass valve on the side of the pump as per the instructions on the Shurflo website which is an easy allen wrench adjustment. Just keep track of the number of turns you make with the allen wrench so you can set it back to where it was, if needed. I have had this problem on two trailers. Changing the check valve did not help.
Before adjusting, I made sure that any water coming back out of the fill tube did not leak to inside the compartment by putting a wrap of thin silicone putty from Lowes around the fitting and the 2 clamps. Then tested by putting filling, putting the cap on and waiting for the overflow. That way it is only a nuisance if it does overflow.
The other adjustment is on the check valve at the front of the pump, you can adjust it to lower the input water pressure. I just tried this adjustment and will be using my trailer soon and will post back the long term results. This problem needs a solution.
Hope this helps
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Old 04-29-2017, 09:20 PM   #6
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Thank you!


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city water, fresh water, tank, water, water tank

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