Water tank fills when hooked to city water

[Therapy]

I left home with full water tanks. I have good water. Some splashes out of the fill port while driving some times. No big deal. The cap does not seal, I think by design.
I noticed that after about 15 days or so into my trip after using my water a bunch that my water fill port was dripping water. My tanks were full again. I had been overnight on city water.
My water pump was not turned on.
My new pressure regulator was set to 45psi.

I assume the auto close valve in my pump is bad.

Access is through the furnace according to Dutchman phone support.

Is it part of the pump?
Or just in line with the pump?
Does anyone know the exact way to access the area?
2019 Dutcman Voltage 3655. toyhauler. 39'. Last four of VIN-KZ990231

[Old-Biscuit]

If you have a Gravity Fill then Pump INTERNAL check Valve (diaphragm) is not closing allowing backflow thru pump when on City Water

Sometime just using the Pump and a tank of water will flush any crud off of diaphragm and let it fully close
*using pump ---- if check valve is not closing pump will short cycle due to loss of system pressure back thru pump

Check Valves are a repair item...disassemble of pump required

OR a $10/12 1/2" in-line check valve installed on pump suction option




If you have a FILL valve (swap from city water to FILL) then that valve could be leaking thur

[Therapy]

Originally Posted by Old-Biscuit

If you have a Gravity Fill then Pump INTERNAL check Valve (diaphragm) is not closing allowing backflow thru pump when on City Water

Sometime just using the Pump and a tank of water will flush any crud off of diaphragm and let it fully close
*using pump ---- if check valve is not closing pump will short cycle due to loss of system pressure back thru pump

Check Valves are a repair item...disassemble of pump required

OR a $10/12 1/2" in-line check valve installed on pump suction option


If you have a FILL valve (swap from city water to FILL) then that valve could be leaking thur

Thank you. Will use tank water and cycle pump multiple times and listen for short cycling.

Not sure what last line info is.
I have a female hose connection for city water and a seprate cap on a tank fill inlet. I use a cut off hose to stick in that hole/tube to fill tanks.

[Martian]

This may be a little overkill but I went with a Sharkbite check valve with a low opening pressure and a very high resistance to backflow. No more issues even if the pump valve fails.

[GypsyR]

Originally Posted by Therapy

Not sure what last line info is.
I have a female hose connection for city water and a seprate cap on a tank fill inlet. I use a cut off hose to stick in that hole/tube to fill tanks.

My coach does NOT have a gravity fill option. Instead I have a switch valve that I leave in the "city" water position unless I want to fill my tank and then I turn it to "FILL". And when the tank is full enough I have to turn it back to city.

That valve on my coach apparently had a leaky internal o-ring and overnight on city water would very slowly fill my tank until it overflowed (and a neighbor noticed and shut the water off.) New o-rings fixed it. Since you have gravity you may not also have the option of filling with city water through such a valve, we have no way of knowing. But since you didn't quite get what "FILL" valve meant then I expect you do not.

[Therapy]

Originally Posted by GypsyR

My coach does NOT have a gravity fill option. Instead I have a switch valve that I leave in the "city" water position unless I want to fill my tank and then I turn it to "FILL". And when the tank is full enough I have to turn it back to city.

That valve on my coach apparently had a leaky internal o-ring and overnight on city water would very slowly fill my tank until it overflowed (and a neighbor noticed and shut the water off.) New o-rings fixed it. Since you have gravity you may not also have the option of filling with city water through such a valve, we have no way of knowing. But since you didn't quite get what "FILL" valve meant then I expect you do not.

Got it. Thanks. I can be easily confused these days.

[Therapy]

Originally Posted by Old-Biscuit

If you have a Gravity Fill then Pump INTERNAL check Valve (diaphragm) is not closing allowing backflow thru pump when on City Water

Sometime just using the Pump and a tank of water will flush any crud off of diaphragm and let it fully close
*using pump ---- if check valve is not closing pump will short cycle due to loss of system pressure back thru pump

Check Valves are a repair item...disassemble of pump required

OR a $10/12 1/2" in-line check valve installed on pump suction option




If you have a FILL valve (swap from city water to FILL) then that valve could be leaking thur

Pump does not short cycle.
I remember now that while on the trip it did not short cycle at night.
I am sensitive to a pump short cycling on a sailboat in the past. If we forgot to turn it off after use it did that. Mfgr used sink pump that was labled "not for use in pressureized systems".

[Tomahawk]

Originally Posted by Therapy

I have a female hose connection for city water and a seprate cap on a tank fill inlet. I use a cut off hose to stick in that hole/tube to fill tanks.

With that system it has to be water getting past the check valve, as Old Biscuit said. You didn't say if this was a one time issue or recurring. It could be that the check valve had debris on it that is now cleared and that is why it does short cycle. At the end of the video the guy mentions winterizing valves as potential culprits as well. I never winterized so I don't know how that might work.

Nice Youtube

video

[Therapy]

Originally Posted by Tomahawk

With that system it has to be water getting past the check valve, as Old Biscuit said. You didn't say if this was a one time issue or recurring. It could be that the check valve had debris on it that is now cleared and that is why it does short cycle. At the end of the video the guy mentions winterizing valves as potential culprits as well. I never winterized so I don't know how that might work.

Nice Youtube

Thanks.
Spoke to Pentair (fast response, spoke english ) contracted tech company and followed their advice and replaced the valve cover unit. They said often it is not just the check valve. They don't sell parts either.
So I just replace the complete upper housing. Most places had it for $44 or more. Amazon, suprisingly even for them, had it for $29.

[Therapy]

Thanks all. Sure hope it is not a winterizing valve. I have them but have never used them since I bought the unit used. It was winterized in Arkansas when I bought and I have put 5-6k miles on it over 3 years and ~8,000miles.