Priming the water pump

[kfp673]

Hello all- We have a 6 year old travel trailer and over the past few years we have had an annoying issue with the water pump that I am getting really frustrated with now. If the unit sits for a period of time with an empty tank, or if we camp with hookups in between outings where we use the tank, I can't seem to get the pump to prime on its own the next time we try to use it. It will turn on with a quiet hum and never do anything. When this happened in the past I used to be able to put my finger or something else in the outside tank vent hole for a minute and then release and that would work but I have not been able to make it work. The only thing I can do, and have been doing, is to disconnect the inlet hose from the pump, put a funnel directly into the pump and pour water in and reconnect the hose. That seems to cause a prime that then works as long as we keep the tank filled and keep using it.

Any idea why the pump no longer primes on its own the way it should? Thanks!

[LouLawrence]

Most RV's have the tanks under the floor and the pump on the floor. so most rv water pumps are above the tank. Truck campers would be a large exception for the most part though.

Most? I have never seen a class A or class C with that kind of setup. I do now understand that this was the OP's setup, however.

[debrhardt]

after 18 years the old pump gave out. bought a new shurflo 4008 on amazon lat year but mine was only $46. amazon is pretty crafty. if the website determines that you have been looking at things previously, the price goes up. they must figure that we are getting desperate.

[StirCrazy]

LouLawrence wrote:

What I don't understand is how you can disconnect the input line and not have water flowing everywhere. That line should be full of water and supply lots more water to your pump than a funnel could provide. Is the pump above the tank?

Most RV's have the tanks under the floor and the pump on the floor. so most rv water pumps are above the tank. Truck campers would be a large exception for the most part though.

[whjco]

wa8yxm wrote:
I agree with the new pump only that price seems high (But then it's been some years since I replaced one.

One make sure fresh tank is FULL

Two.. open faucets. Kitchen and bath before turning on pump.

3 Insect lines for valves and holes.

I just paid $72.50 for a new SureFlo pump on Amazon. I also bought a new replacement valve assembly for the old pump for $13.13 so now I have a spare pump.

[whjco]

IB853347201 wrote:
For about $70 you can buy a new Shurflo pump on Amazon and be done with your issue,,,just saying,,,

And for an additional $14 you can buy new valves for the old pump and have a spare. (I just did this).

[gtnsmlr]

wa8yxm wrote:
I agree with the new pump only that price seems high (But then it's been some years since I replaced one.

One make sure fresh tank is FULL

Two.. open faucets. Kitchen and bath before turning on pump.

3 Insect lines for valves and holes.

Opening the faucets works everytime

[wnjj]

A few years ago I found the water pump had been left on in storage. Once the tank level had evaporated enough it was running continuously for days/weeks/months. While diaphragm pumps can be run dry for at least a while, it never was the same. It would no longer prime unless the tank (located below it) was almost full. It would lose prime when traveling.

I cheated for a couple years when I found you could put the winterizing valve half way between settings and suck tank water up into the winterizing tube with your mouth. Then I could get the pump to prime if I opened a faucet, ran the pump while on winterizing mode AND while blowing as hard as I could into that tube. Once it started to take I could switch back to tank and it would prime up. Once primed, it would last the whole time we stayed in that spot and didn’t leak down or run unless a faucet was open.

I took the pump apart 2x looking for issues or debris in the diaphragm but it always looked and felt fine. Finally I decided to swap the pump and it all works just fine again. This was with the same inlet pipe and filter so it wasn’t an air leak. Obviously the diaphragm just couldn’t pull enough of a vacuum when dry.

[1320Fastback]

When filling from dry tanks I usually open the pressure release on the water heater. As the tanks fill eventually the water heater fills and water will spit out. Then I close the pressure release and continue filling the tanks. Once they are full I pull the kitchen drawers out and make sure the water filters have water in them. If not I remove them and fill them up, sometimes I change the filter cartridge also. Tighten up the water filters and then open the bathroom faucets and kitchen faucets and turn the pump on. Generally it primes somewhat quickly. Do remember a few times I was wondering if it ever was going to though.

[opnspaces]

The next time it happens I would disconnect both the inlet and outlet and use my fingers to plug the ports with the pump running. If it's a bad diaphragm it should be obvious.

[Veebyes]

Disconnect at the output side of the pump. Hold your thumb over the pump outlet & turn it on. Pressure? Yes? Suction is fine. No? No suction. Trace backwards. Pump itself plus fittings. It does not take much for an air leak on the low pressure side.

[wa8yxm]

I agree with the new pump only that price seems high (But then it's been some years since I replaced one.

One make sure fresh tank is FULL

Two.. open faucets. Kitchen and bath before turning on pump.

3 Insect lines for valves and holes.

[LouLawrence]

kfp673 wrote:
The only thing I can do, and have been doing, is to disconnect the inlet hose from the pump, put a funnel directly into the pump and pour water in and reconnect the hose. That seems to cause a prime that then works as long as we keep the tank filled and keep using it.

Any idea why the pump no longer primes on its own the way it should? Thanks!

What I don't understand is how you can disconnect the input line and not have water flowing everywhere. That line should be full of water and supply lots more water to your pump than a funnel could provide. Is the pump above the tank?

[2112]

I have a similar issue after I drained the lines for winter. I turn on the bathroom cold faucet (closest faucet to the pump) and problem solved.

I turn the faucet off once all the air sputters out.

[kfp673]

Thanks all. I have checked to make sure no fittings are obviously loose or have any obvious issues which I can't find. Everything is snug. Must be an air leak somewhere but maybe I'll just try a new pump. Won't be happy if it behaves the same but if they are in the $70 range it's probably worth a try. Thanks!