Confirming Bad Water Pump

[PatAndMarkRoadT]

I think I have a bad water pump but wanted a second (or third) opinion before I start the job.

Here are the symptons I encountered while dewinterizing and working to flush the lines:
1. Freshwater tank full.
2. Pump motor running (by sound and vibration)
3. No pressure building up.
4. Checked lines for leaks or missing caps using external water pressure. System is sound and sealed (best news of the day).
5. Shifted my pump inlet valve to Winterizing and drew no suction on a pan of water.
6. Based on number 5 above, I am convinced I do not have a priming problem or obstructed line to the full freshwater tank.
7. Conclusion: I have a bad pump and need to extract the motor/pump and replace the pump.

Would love to hear other proposed troubleshooting steps or alternate repairs before I open up the system this weekend.

Thank you in advance.

[Almot]

All these symptoms may be caused by another problem:
You have an air leak and need to seal it.

Plastic parts forming the head have developed a tiny crack on the seam. Take the head apart and tighten it back again. Worked for ScottG, worked for me, might work for you. If tightening doesn't help, put some sealant on.

Plastic warps, cracks appear. You buy a new pump and it may develop same problem. It just happens with time, even without use, while in storage.

[Gjac]

What make and model water pump do you have? After a trip to Az. in the winter when temps got into the teens my Sureflow 4088 pump did the same thing. After taking it apart, cleaning and reassembling it several times I finally realized the problem was not the diaphragm it is pretty thick durable rubber, it turned out to be a small air leak along the parting plane and no amount of tightening the screws would stop the leakage. After adding some silicone sealant along the parting plane the pump worked fine.

[A_Good_Cigar]

I had/have this problem on my Suncruiser occasionally. If the pump loses it's prime I have no on board water supply. In that case I completely top off the fresh water tank and take if for a short drive with a faucet open & the pump on. Sometimes the jostling from the drive will prime the pump. Last month that didn't work for a boondocking trip, and I discovered a faster way. On my RV, the pump is fully exposed & accessible. After removing & cleaning the pump head (no change) I removed the pump discharge hose from the junction and gave it a small suck, and almost immediately I was getting a bath! As long as my water pressure is good from the faucets & shower, I see no need to replace the pump just yet, it's a two minute job to prime the pump at the hose. Good luck:)

[bguy]

Turn the valve to winterize and fill the hose with water while elevating the end to get the water down to the pump. That's how I got my friend's pump to prime year before last. I've never had to open faucets ut I'm sure it can't hurt.

[ScottG]

When ever a pump has failed to prime for me, I take the head apart and rinse off all the parts and it works fine after that.

[garyemunson]

I've had issues with the black plastic valves inside the pump chamber sticking. In my case, just taking it apart, working the valves with my finger under running water dislodged whatever tiny piece of trash that was causing it to stick and it washed away unseen. Worked fine after that. Worth a try if nothing else works.

[wa8yxm]

I had to replace mine for other reasons. Easy to do

Check the INLET strainer on the pump.. (it is on the inlet side)

I like other suggestions too

Drained my water heater back on Ohio when the weather was getting too cold and I did not wish to risk the tank to a freeze.. WHen I re-charged it.. TOOK "Forever" or so it seemed to expell all the air and give me hot water.

[wnjj]

Mine's been doing exactly what the OP describes for the past couple of years. To re-prime it I have to turn the winterizing valve half way. I can then suck on the winterizing hose and fill it from the tank. Then I switch the pump to full winterizing mode and have to blow pretty hard into the tube of water (with a faucet open and pump running) before it will catch and start pumping. Immediately after the hose runs dry I switch to the tank and it will continue priming.

I've taken the diaphragm apart a couple of times and there's nothing obvious wrong. A new pump is cheap enough that I'll eventually do that if I can't find anything else wrong.

[Halmfamily]

Old-Biscuit wrote:
Turn pump on........open a faucet and let it run (air is system has to be expelled before pump will move water)

X2. Had the same issue as you are having. I opened kitchen faucet and let pump run and after ten minutes or so I had water.

[Lwiddis]

Age of RV? Age of pump?

[Old-Biscuit]

Turn pump on........open a faucet and let it run (air is system has to be expelled before pump will move water)

[DutchmenSport]

If yours has the plastic little bowl with the screen filter on it, right at the inlet of the pump, it's possible that little plastic bowl is cracked. If you have one, and it did not get emptied out, its possible water in it over the winter could have cracked the plastic and therefore, it's sucking air.

[Ski_Pro_3]

It might just be a priming issue. Try this; turn on pump, open faucet at the kitchen sink, put your mouth over the faucet outlet and give it a good suck. If you are drawing air, not good and most likely the diaphragm in the pump is shot. If you can suck water but still won't pump, most likely the motor needs servicing.
Mine did like yours and I could restart it by priming the lines with a good suction when the faucet was open and the pump on. It would loose prime if left without operation after a day or so and I'd have to do again. Turned out my winterizing valve had cracked threaded fixtures. All three of them! I removed the winterizing valve and used a faucet hose from Home Depot to 'hard wire' it. In winter, I unscrew and hard wire it the other way.

[SoundGuy]

Disconnect the intake and output water lines from the trailer and see if it acts the same. Chances are it's fine, in which case you have a leak somewhere in the trailer that's preventing the pump from building pressure.