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Old 04-17-2019, 10:37 PM   #1
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THOR #6826
Fresh water pump issue

Well, I unwinterized my Class A today. Everything works properly except the fresh water pump doesnít shut off. By way of diagnostics I disconnected the output side of the pump. Get a super volume of water flow. Then I tried capping the output side of the pump. Pump still runs so I conclude itís not a downstream leak (whew!). Next I tried feeding the pump from a bottle of water through the winterizing valve with the output capped by a pressure valve. I.e. the pump was completely isolated from the RV. The pump ran for a moment and shut off normally and the pleasure gauge read 44 lbs. From this I conclude that the pump is fine. So now Iím left to conclude that the only remaining possibility is that the pump is sucking air somehow from the single PEX pipe that leads from the fresh water tank to the winterizing valve. Or the check valve that prevents back flow through the pump when on city water. Am I missing anything? Any other possibilities?

My RV does not have a tank fill valve. It is a gravity fill only. Everything works fine on city water.

If itís the check valve would capping the city feed connection prevent the pump from sucking air?

And/or would disconnecting the output side of the pump and seeing if there is any discharge through the pump when on city water be the definitive test?

I havenít located the valve yet - itís dark, crowded and messy in there! But there has to be one....

As always, I appreciate the help of my forum friends,
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Old 04-17-2019, 11:24 PM   #2
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THOR #2631
Well you have done a lot of good trouble shooting already. Initially I thought bad pressure valve in the pump, but then you drew water from the external bottle via winterization line with a capped output on the pump.....and the pump stopped running and held pressure. I assume your pump filter has been cleaned and is located between the pump and your winterization line / freshwater line T, which is typical......which would prove its not leaking air. So to me itís pointing back toward the fresh water tank either not full enough with water or air leak in the feed line before the winterization valve (which is what you suggest also I think). Make sure the fresh water tank air vent is not blocked with water or just open the fill cap for your pump testing (so no vacuum forms behind any water in the tank). The fact that water is flowing out the pump in one of your tests may be mostly gravity feed perhaps? On my coach there is a shut off valve on the fresh water tank (gravity fill FWT also) and a shut off valve on the winterization line........so I have to close one and open the other depending on which liquid source I want to use.
To check the backflow valve in the pump you should connect the pump to the normal coach lines; turn on city water and open the winterization line. Make sure the FWT line is closed. any city water coming through the winterization line means a backflow valve problem.
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Old 04-17-2019, 11:42 PM   #3
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THOR #11130
Things I would double check:


Water Heater plug back in and secure
Water Heater "bypass" back in correct position
Input and Output line to water heater in open position
Water Heater actually filled back up with water
Low Point Drains all closed off
All faucets turned off including outside shower
Winterizing cap back in place and tight
Water shut-off valve between tank and pump in open position
Tank actually has enough water for pump to prime up
Input line to pump isn't sucking air



You've probably done all this but two half brains hopefully will make a whole one.
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Old 04-18-2019, 02:34 AM   #4
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Good thoughts all. I appreciate the input. I find I donít noodle through this sort of issue like I used to! This used coach is new to me over the winter so Iím still exploring. I donít think there is a valve between the FWT and the pump other than the winterizing selection valve. It would be a likely source of the problem if there is. One thing I didnít try is feeding the coach from my freestanding bottle through the winterizing valve. Iíll do that this weekend and if it operates properly it will pretty much leave me with the waterline from the FWT sucking air. BTW, my freshwater tank was full to the brim. Itís interesting to me that the pump was replaced by the previous owner even though the coach is barely three years old. Wouldnít surprise me a bit if this is the reason! But Iíll figure it out. Itís not ďrocket surgeryĒ
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Old 04-18-2019, 02:53 AM   #5
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Hi Pete'sMH, so you fed the pump directly from the water bottle......did the water also pass through the pump filter, or did you bypass that too? If you bypassed the filter I would suspect the filter is not sealed or has a hairline crack more than the water tank.....especially when you say it was full.
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Old 04-18-2019, 03:05 AM   #6
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Originally Posted by javelin View Post
Hi Pete'sMH, so you fed the pump directly from the water bottle......did the water also pass through the pump filter, or did you bypass that too? If you bypassed the filter I would suspect the filter is not sealed or has a hairline crack more than the water tank.....especially when you say it was full.


Was my first thought as well. But, alas, the filter is between the winterizing valve and the pump so it passed the test.
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Old 04-18-2019, 05:43 AM   #7
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Quote:
Originally Posted by Pete'sMH View Post
Well, I unwinterized my Class A today. Everything works properly except the fresh water pump doesnít shut off. By way of diagnostics I disconnected the output side of the pump. Get a super volume of water flow. Then I tried capping the output side of the pump. Pump still runs so I conclude itís not a downstream leak (whew!). Next I tried feeding the pump from a bottle of water through the winterizing valve with the output capped by a pressure valve. I.e. the pump was completely isolated from the RV. The pump ran for a moment and shut off normally and the pleasure gauge read 44 lbs. From this I conclude that the pump is fine. So now Iím left to conclude that the only remaining possibility is that the pump is sucking air somehow from the single PEX pipe that leads from the fresh water tank to the winterizing valve. Or the check valve that prevents back flow through the pump when on city water. Am I missing anything? Any other possibilities?

My RV does not have a tank fill valve. It is a gravity fill only. Everything works fine on city water.

If itís the check valve would capping the city feed connection prevent the pump from sucking air?

And/or would disconnecting the output side of the pump and seeing if there is any discharge through the pump when on city water be the definitive test?

I havenít located the valve yet - itís dark, crowded and messy in there! But there has to be one....

As always, I appreciate the help of my forum friends,
When my Shurflo water pump was acting up I went to the pump web site and found the 5/64 ajustment allen screw on my pump. Also found a You Tube video . I was able to get it taken care of. Hope you get your issue fixed .
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Old 04-18-2019, 06:47 PM   #8
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Originally Posted by ddlonewolf50 View Post
When my Shurflo water pump was acting up I went to the pump web site and found the 5/64 ajustment allen screw on my pump. Also found a You Tube video . I was able to get it taken care of. Hope you get your issue fixed .


Thatís an idea. Iíll check to see if turning down the cutoff pressure helps. If it ever quits raining. Thanks for the suggestion.
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Old 04-18-2019, 09:10 PM   #9
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Curious if you get water flow from any of the faucets when the pump is running. I know you got it when the line was disconnected but what about when it is connected. I have had the situation where the pump wonít shut off until the air is out of the lines. I opened the faucet and got a good water flow from all the faucets and then the pump would shut off.
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Old 04-18-2019, 09:45 PM   #10
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THOR #13399
Let all sources run hot and cold water to make sure all air is out of system especially outside shower and ice maker washer if you have them, otherwise pump is compressing air
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Old 04-19-2019, 12:12 AM   #11
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THOR #6826
Yup, got water out of all faucets, hot and cold. Ran all the pink stuff out and Iím confident the air as well. Operated on city water and pump. I did think the volume/pressure on the pump was somewhat low. Soon as it stops raining Iím going to try running the coach on my water bottle through the winterizing port. If the pump operates properly (I.e. shuts off) Iíll have some important new data. From my previous testing I think this might be the case. Hoping anyway! Really like how helpful this forum is.
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Old 04-19-2019, 09:24 PM   #12
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THOR #6826
Think Iíve got it! My pump worked fine - shut off and stayed off when feeding the coach from a water bottle through the winterizing port. There is a plastic right angle fitting in the PEX line from the FWT to the pump inlet and it is wet. Donít know how it might have come to leak but Iím betting thatís my culprit. Iím going to replace it with a Sharkbite fitting but I canít test it while the coach is at the storage lot (canít fill the water tank).

Thank you all for your ideas and encouragement. Time to get on the road!
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Old 04-19-2019, 10:09 PM   #13
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Great! Hope the SharkBite does the trick.
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Old 04-19-2019, 10:13 PM   #14
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Great way to work thru a problem
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Old 04-20-2019, 12:13 AM   #15
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Great work and a good learning entry for others on the forum. Water pump issues can be very frustrating. Low pressure side air leaks can sometimes be real hair pullers to find.
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Old 04-20-2019, 03:44 PM   #16
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That fitting may have held enough water to freeze... In my prior Mh, the faucet line between the handles in the shower froze and cracked. Only leaked inside the wall when shower was in use.
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Old 04-20-2019, 08:06 PM   #17
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Originally Posted by Hooligan2 View Post
That fitting may have held enough water to freeze... In my prior Mh, the faucet line between the handles in the shower froze and cracked. Only leaked inside the wall when shower was in use.


Likely. Or just a bad connection to the PEX. I hope for a full forensic analysis once Iíve removed the fitting. Which Iíll do if it ever quits raining!! Scheduled for our first short local trip next week and Iíd really like my water system work properly.
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Old 04-21-2019, 02:09 AM   #18
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Prior RV was 36ft DP, GeorgieBoy Landau. New in 2000, after about 10 years all the plastic PEX fittings were brittle and began to crack, I replaced ALL the fittings with brass and SS crimps. I was surprised I could access all the plumbing.
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