Water Pump Priming Issues

[OldKingKibitzer]

When disconnected from City water- trying to run my pump (My fresh water tank is 1/3 full) my pump will just run and run and run....And eventually work. Once it's primed itself it seems to be running fine.

Is there a way to check to see if it's not priming correctly? Is this a sign it's on its way out? Any maintenance that I should be doing

2013 Fuzion 310

[chuckster57]

Do you have 2 fresh tanks like some toy haulers? If so then you need to know which tank has the primary fill port and which one has the sensors. If you only have 1 fresh tank then disregard.

Try filling to 2/3 and see if it does the same thing. If so then it might be time to rebuild the pump head or replace it. There isn’t any maintenance per se to do on a fresh water pump. One last thing to check is the fittings at the pump, you might be sucking air but I doubt it.

[flybouy]

Do you know how long it runs? Is it 20 seconds, 10 min.? Your description isn't really helpful.

[JRTJH]

RV water pumps need a "demand" before they will prime. If you turn on the pump without opening a faucet, it will "cavitate" and continue to run as it "very slowly builds pressure"...

To avoid that problem, when you turn on the pump, open a faucet or press the foot flush on the toilet. That will create a demand for water and the pump can pull water from the tank more easily, eliminating the "cavitation and prolonged running without priming"....

[GHen]

I agree, the pump is designed to push and pull, but it can’t if air is being held at the pump, opening any valve will allow the pump to push the air out of the pump and pull water from the tank. The tank is also lower than the pump, so the tank could be full and still not be able to “prime” the pump.

It could need a rebuild, depends on how old it it and how much it has been used.

[OldKingKibitzer]

Last time I tried running the pump it took about 10 mins to finally prime and pump water. I leave faucets open when I turn it on to make sure that the air isn't getting into my pump and allow it to push water through.

What about emptying the water tank completely? I make sure that it's empty between uses- Could that be part of the issue?

[JRTJH]

If you've got a faucet open and turn on the pump to find it won't prime, either you've got a leak at a fitting on the pump inlet side (sucking air rather than water), a crimped hose on the inlet side or a defective pump head.

I'd first suspect a leaky or loose fitting. If it's a FloJet pump, you may not have the inlet fitting "locked in place". There is a blue "push plug" that fits in a groove on the fitting. It will appear to be locked in place when really, the fitting is not fully pushed into the pump. That will allow air to flow into the pump, preventing the vacuum needed to draw water up the hose and into the pump head.

Second, if there are no loose/leaky fittings is a crimped or excessively bent hose.

Third, you may have a defective pump diaphragm. Sometimes they just fail. If the pump is less than 2 years old, you can get a replacement from FloJet (2 year warranty). If it's older than 2 years, you can order a replacement pump from Amazon for around $45.