RV Water Pump Briefly Runs With No Water Use

[bigbAZ]

So this just started and I can't find any leaks when the pump is on or when connected to city. If I leave the pump on with no water usage, after a few minutes it will run very briefly like a 1/4 second. It will also run for a short burst if I switch it on after it has been off for awhile with no water use.

I'm going to attempt another leak check soon but I am wondering if this could be caused by a weak or dirty check valve at the pump causing pressure to drop, or does it mean there is definitely a leak? It has never done this in the past, just started this season. Pump is original from 2011 and I have no accumulator in the system.

 

[8Muddypaws]

Pressurized water is probably leaking back through the pump. There’s supposed to be a check valve to prevent that. There are several different designs as well as some pumps with them integrated into the pump itself.

Another theory is the check valve that keeps pump water from flowing back into the city water inlet

 

[bigbAZ]

Another theory is the check valve that keeps pump water from flowing back into the city water inlet

Is that located right where the city hose screws on? I did notice the other day it was wet there and it had been quite a while since I had disconnected the hose. Tomorrow I'll see if it's dry and if so, I'll switch on the pump and see if it drips.

 

[Rene T]

Is that located right where the city hose screws on? I did notice the other day it was wet there and it had been quite a while since I had disconnected the hose. Tomorrow I'll see if it's dry and if so, I'll switch on the pump and see if it drips.

Remove the screen in that inlet and you’ll see a ball which is a check valve.Using a soft tool like an eraser on the tip of a pencil with No pressure and push in on the ball. Then start the pump and as the pressure increases, continue pushing in the check valve to flush out anything that may be in there. Get ready to get wet

 

[John From Detroit]

IF it's leaking a short term solution is the screw in plug most RV stores sell as well a many "Automotive" department RV aisle (Wal*Mart for example) Or a brass one from the hardware (My choice) as back up for the check valve.. The valve is usually easy to replace (That is you replace the entire inlet assembly, generally 3 screws and one plumbing fitting. also threaded.

 

[Gary RV_Wizard]

There are three places where invisible water pressure leaks can occur.

1. Thru the pump body itself, where the water drizzles back through the pump and into the fresh tank once the pump shuts off. Just about all RV fresh water pumps use the type of design that is susceptible to that sort of failure.
2. If the RV has a pump bypass valve (aka "city fill") that enables filling the fresh tank from a hose attached to the freshwater hose inlet, that valve can have a tiny leak. That will allow water to flow back into the fresh tank whenever the system is pressurized. This i a fairly common type of problem. If the pressure is being maintained by the pump, the pump will cycle occasionally. That merely recirculates fresh tank water back into the tank. If the pressure is maintained by hose on the inlet, then incoming city water leaks through that valve and eventually will cause the tank to overflow.
3. There is a check valve at the city inlet that is prone to leakage from damage or sediment in the city water. If no hose is connected, you will see drips from the inlet, but if a hose is connected, the leakage goes into the hose. However, that can't happen if there is enough water pressure in the hose to counteract the pump pressure.

The easy way to detect #3 is to simply disconnect the hose and watch for drips at the city inlet. If it appears, follow Rene's advice in post #4.
#1 & #2 are difficult to distinguish from each other but unless the pump is quite old, odds favor #2 as the source of the problem. Disconnect the hose from the pressurized side of the city fill valve and cap it off to see if the problem goes away.

 

[Kirk]

Gary has covered it well, but I'll add a little.

Pump is original from 2011

Since the pump is now 15 years old, I suspect that the pressure is leaking back through the pump, as Gary said in #1. That is quite common and if so, it can be easily resolved with a pump rebuild kit that is available for most RV water pumps, or you could also just add a check valve to the inlet side of the pump. Because the pump cycles via a pressure switch on the pump, the check valve must be on the suction side of the pump to prevent back flow through it but maintain the pressure inside of the pump. The other option would be to just replace the pump, which isn't difficult.

IF it's leaking a short term solution is the screw in plug most RV stores sell

The threaded plug is something that I and many others use just as a matter of course as it not only prevents any water leakage back from the RV when city water is not connected, it also keeps the fitting clean. You can usually find those plugs at any home supply or hardware store, RV supply store, Walmart, or Amazon.

 

[DutchmenSport]

I had a Keystone Outback travel trailer that started doing that. Over time the short bursts became more and more frequent. I could not find any leaks either.

Long story short: It turned out to be the water pump itself. 2 of the 4 screws that hold on the actual propeller part and come completely out. I found one on the floor below the pump, never did find the second one. The only solution I had was to purchase a new water pump. I still have the old one, but still only has 3 screws. After I replaced the pump, it never pulsated again.

My current fifth wheel pulsates also for 2 reasons: The ice maker draws water and the electric Bidet in the toilet releases water occasionally to ensure the heating element inside it always have water so the element won't burn out. Each one causes a pulsating.

You might check your toilet. You can have a leak there, water going in the bowl and you'd never know it. It only takes about 3 ounces of water, difference in water pressure, to turn the water pump on and off. That's a tiny bit of water because there are no pressure tanks equipped in our campers, unless one is put there after-market.

 

[Rene T]

Just to add one thing to my post #4. If you remove the screen, take a good look at it. If it is dirty, just replace it. You can gat them at any hardware store. Do not run water into the rv ever without a screen there.

 

[bigbAZ]

Well here's what I did:

I had a brass 45 screwed into the inlet so my hose would have a gentle bend when connected as the inlet is inside of a compartment and the hose goes through a little door in the floor of the compartment. I removed the brass 45 and it was very tight.

There was no screen, the one way valve was plainly visible. It was bone dry. I then switched on the pump and left it on for 15 min, the valve remained dry and the pump did not cycle like it has been for the last 9 days of my recent trip. I then kept checking all morning, each time I'd switch the pump back on it would not run, the pressure was still holding and the inlet was still bone dry.

After 4 hours it was still holding pressure. Next I screwed the brass 45 back on using a dab of faucet grease on the threads, and I got it tight but not overly tight. I switched on the pump, it was still holding pressure. I waited 4 more hours. No drips, still holding pressure.

So it is "fixed" for now. All I can figure is that I may have had the brass 45 tight enough to deform the inlet enough to make it leak. I am not worried about the screen, I don't know if it ever had one. I never hook up water without a Camco Taste Pure filter which won't let any debris reach the inlet, or my pump.

 

[Rene T]

Did you have a rubber gasket just before the 45. Maybe the 45 was compressing the gasket to a point where it pushed up against the check valve.
Read my post #9 entirely. You need a screen there. It will catch any dirt from the incoming water supply. If you don’t, Eventually that dirt will find its way to all your faucets and plug them up. That would be a bummer especially the shower head where it has very small holes

 

[bigbAZ]

Did you have a rubber gasket just before the 45. Maybe the 45 was compressing the gasket to a point where it pushed up against the check valve.
Read my post #9 entirely. You need a screen there. It will catch any dirt from the incoming water supply. If you don’t, Eventually that dirt will find its way to all your faucets and plug them up. That would be a bummer especially the shower head where it has very small holes

I see on the internet they all have screens. Mine must have been removed by a previous owner. I'll have to pick one up. I'd like to replace the entire valve but the backside is not easy to access, involves reaching through a trap door under the bed with one long arm, can't fit 2 arms in there. Can't see once one arm is in there. I replaced the outside shower valve a few years ago and that was about 8" closer than the inlet and a real stretch (literally) not sure if I can even reach the inlet.

I'm wondering how anything can get past my filter though, unless I let dirt get into my potable hose.

 

[Jimdamedic]

So here is an addition to the never ending list of mistakes I have made since owning a 5th wheel. Dewinterizing this spring and i was sanitizing the lines. The pump ran and ran and did not shut off. No leaks visible anywhere. Very low pressure with almost no flow. Everything was fine when hooked up to city water. I searched and searched found no peaks and thought the pump must be bad. I purchased one and just before i installed the new one, did one last check of everything. I realized that i hadn't turned off the winterize bypass. It was trying to pull through that. Sigh. I am now the proud owner of a spare water pump.

 

[bigbAZ]

So here is an addition to the never ending list of mistakes I have made since owning a 5th wheel. Dewinterizing this spring and i was sanitizing the lines. The pump ran and ran and did not shut off. No leaks visible anywhere. Very low pressure with almost no flow. Everything was fine when hooked up to city water. I searched and searched found no peaks and thought the pump must be bad. I purchased one and just before i installed the new one, did one last check of everything. I realized that i hadn't turned off the winterize bypass. It was trying to pull through that. Sigh. I am now the proud owner of a spare water pump.

I bought a spare as well figuring someday I'll need it. I wrapped it in bubble wrap and stashed it under the bed where the pump is mounted.

 

[John From Detroit]

So here is an addition to the never ending list of mistakes I have made

......
Now when you are out boondocking it's 6pm on a Friday and all the RV stores for 100 miles are closed for the 3 day holiday weekend and you pump fails... All set you are.

NOT a mistake.

Had a camper who's AC was making all sorts of noise..> Found out the squirl cage blower was cracked. Seee time of day / week above.. Well I used to have that same make and model and when it failed I kept the good parts.. Just a minute and I came back up the ladder holding a spare I did not need.

Same Idea figured it was going to be needed.

 

[Rene T]

So here is an addition to the never ending list of mistakes I have made since owning a 5th wheel. Dewinterizing this spring and i was sanitizing the lines. The pump ran and ran and did not shut off. No leaks visible anywhere. Very low pressure with almost no flow. Everything was fine when hooked up to city water. I searched and searched found no peaks and thought the pump must be bad. I purchased one and just before i installed the new one, did one last check of everything. I realized that i hadn't turned off the winterize bypass. It was trying to pull through that. Sigh. I am now the proud owner of a spare water pump.

Return it

 

[RayIN]

I see on the internet they all have screens. Mine must have been removed by a previous owner. I'll have to pick one up. I'd like to replace the entire valve but the backside is not easy to access, involves reaching through a trap door under the bed with one long arm, can't fit 2 arms in there. Can't see once one arm is in there. I replaced the outside shower valve a few years ago and that was about 8" closer than the inlet and a real stretch (literally) not sure if I can even reach the inlet.

I'm wondering how anything can get past my filter though, unless I let dirt get into my potable hose.

We bought a new 5er and I sanitized the plumbing. After I ran the bleach solution through the lines, the pump flow went down to a trickle.
The pump screen appeared clean, so moved to other areas, which were all clean.
Finally I decided to remove the pump screen; it was filled with clear plastic cuttings from construction/assembly of the fresh water tank, but could only be seen when I emptied the filter screen into my hand.
We've all been there or will. hang in there.