Need help diagnosing continually cycling water pump in '96 Roadtrek

[VTPete]

Hi All!

After de-winterizing my RV and taking it on a several day trip, I noticed a new problem has developed.
YouTube Video

The water pump keeps turning on every few seconds for about a second. The video shows it better than I can describe.

I've checked the external shower, toilet, water heater and sink for possible leaks and I don't see any at all. There's no sign of even a drip coming out from the places I can visibly check.

Does anyone have any hints on what might be happening or how I can diagnose it? This is the original pump.

When in actual use, the pump and water pressure are just fine. For now I'm just turning off the pump when I am not using it.

-Pete

 

[goodtogo-ClassB]

Did you clean the filter? Make sure you get all the air out 100% from everywhere. Sometimes the slightest air in one of the hot or cold lines will do this.
Try filling the water tank 100 % + and see if that helps with the pressure.
Good luck

 

[GroupB]

My guess is a leaking check valve. If so, could be dirty or could be worn out.

 

[ks@yvr]

I’d check all taps and valves on system are properly closed. Don’t forget outside shower, hot water bypass and look closely for a small leak . Pump may be supplying water fine but pressure is being lost quickly. Could be something in pump from tank like grain of sand stuck in diaphragm of the pump. You can disassemble and reassemble the pump by removing 3-4 screws to clean/inspect pump rubber diaphragm. Everything reassembles without much difficulty just don’t over tighten the screws on the pump portion.

 

[VTPete]

Thanks, guys. I've opened all valves (including outside shower) to bleed all air, but it's still doing it. Again, I see no signs of water dripping anywhere. I checked the filter down at the fresh water tank and it's clear as a bell (I replaced it two years ago when I did a full fresh water tank drop and cleaning.)

It looks like the water pump disconnects easily enough from the piping by just unscrewing those connectors. I'll take it apart next to see if anything is obviously wrong with it. Once it's disconnected from the RV I'll also be able to easily test it "on the bench".

I don't know how diaphragm water pumps work - including the way they miraculously pump more when the output pressure drops as you call for more water. It will be fun to learn as I believe this will be the last system in the RV I haven't overhauled, repaired or replaced. Wait, the fridge is working fine and is original, so there's that!

If anyone has a link to any information about servicing these pumps, let me know, ok?
-Pete

 

[VTPete]

Ok, problem solved. The pump kept acting like air hadn't been purged... or there was a small leak. Or, perhaps a bad pressure sensor.
So, I took the pump off, opened it up and saw it looked perfect inside. I adjusted the pressure sensor a bit and that increased the amount of time between when it came on, but didn't solve it.
The solution? Um. Ah. There was still air in the lines. Even though I had quadruple checked... I forgot about one little circuit - the fill valve that allows you to fill the tank and get water from your city water feed. I opened it and heard water rush into the box that contains the outside shower. Running the shower, a blurb blurb blurb of air came out and the pump stopped coming on.
So, in the end there was no problem at all. Just me forgetting about that one little water circuit!

 

[leva56]

I had the same thing happen to me. Was told to turn the adjusting screw counter clockwise just alittle, that did it for me. working fine now.

 

[rtbill-ClassB]

Good that you solved the problem. For others who find this thread, something not mentioned that can drip is the pressure relief valve on the water heater.