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Old 06-16-2014, 09:46 PM   #1
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Water pump runs, but builds no pressure

I have a strange issue and I'll probably need to bring the unit back to the dealer to fix, but it's intermittent and I'm afraid they won't have the issue when I bring it and tell me nothings wrong. I called service and they never heard of this issue, but bring it in blah, blah, blah.

The Issue is that sometimes the water pump seems to loose prime and just spin for hours building no pressure therefore not shutting off. When it's spinning it's very quiet because it's not building pressure and sometimes you don't notice it went to la la land. If I open a water valve water comes out slowly and then soon you hear the pump build pressure and the water flow starts to flow better. This does not always happen 9 times out of 10 the water pump works correctly building pressure and then shutting off like it's supposed to, but occasionally it just turns on and spins.

Any idea what the issue is? All of the hoses seem tight. The antifreeze valve is closed. It seems air is getting into the suction side of the system, but I see nothing wrong. Could this be a bad pump? To drop it off and pick it up is about $100 in diesel plus a couple of wasted days. I'd rather fix it myself if the parts are not too expensive.


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Old 06-16-2014, 10:04 PM   #2
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I would take a gallon jug of water and use the antifreeze tube. If it picks up then the pump is probably ok. You could have an obstruction in the line from the water tank to the pump. Just guessing here.

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Old 06-16-2014, 11:11 PM   #3
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Personally I believe you have air in your lines,
1st, make sure all the low point drains are closed,
2nd, fill your fresh water tank full, then, (water pump off)
3rd, hook to the city water connection, then open every one of your valves, hot and cold all at the same time, showers, in and out, make sure all the air is flushed out, close all the valves, then try the pump again

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Old 06-17-2014, 05:39 AM   #4
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Don't forget to check the outside shower if you have one.
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Old 06-17-2014, 06:45 AM   #5
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You need to bleed air every time you run out of water and refill the tank. That means you open everything one at a time and get the air out. The shower is the one most people miss. I make it a habit to never leave the trailer with the pump switch "ON". If I am on city water I turn it off outside. It's an easy habit to form and one that's best formed before you come back to the trailer with water coming out the door. Most fresh water tanks are large enough to fill the black water tank and most of the trailer floor before you run out of water.
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Old 06-17-2014, 08:42 AM   #6
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Last time out, my pump acted the same way. Would not prime, run with a low hum, etc etc. Finally found a ever so small, smaller than a leak, on the downstream side water line, at the water filter. the cap was not screwed down. End of pump problem.
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Old 07-07-2014, 05:21 AM   #7
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well mine was doing the same thing and I bled the lines then removed filter thinking that was it ,,, didn't help . then started running back towards tanks I had one vent tube pinched on front tank and the rear tank wasn't equalizing with the front tank ... seems there could be other problems but I would go with the obvious first just open each faucet one at a time to make sure water runs without spitting air and go from there
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Old 07-07-2014, 05:47 AM   #8
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winterizing valve left open maybe or bad valve?
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Old 07-07-2014, 07:29 AM   #9
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Experienced similar problem, found air leak at one of the fittings tightened it worked fine.
Also, be sure in line water filter is clean.
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Old 07-08-2014, 08:58 AM   #10
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There is yet another reason why it may not prime. Recently I installed two new 6volt batteries just prior to going on a trip. The electrolyte was just over the plates so I added more water which lowered the voltage somewhat. When boondocking
the pump never saw a good 12 volts which it needed and made a pumping sound but would not prime. Once back home and charged up the pump worked like a champ. This may not be your reason for it not priming but when I read up on the problem this was what was mentioned and the reason for mine not working.

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