Water Pump

[johntk]

2015 Fleetwood 34A

Whenever I begin a trip I turn-on the on-board water pump. It always takes 3-5 minutes to prime itself. Once primed it works flawlessly. This happens regardless of the fresh water tank level.
Does anyone else have a similar situation or know of a fix.
I find it very disconcerting to listen to the pump ratcheting that long before finally stopping once it is primed. I'm afraid it may be damaging itself.

Thanks,
John

 

[Rene T]

Are you by chance filling your water heater at the same time?

 

[NY_Dutch]

First of all to put your mind at ease, the diaphragm pumps used in RV's can run dry for hours with no damage, so don't be concerned about that. As Rene asked, could the pump be filling the water heater tank when you first turn it on? Also, is your pump located above or below your water tank...

 

[johntk]

Thanks for the replies.
1. Hot water tank should always be full. I do not do anything to it before turning on the pump (i.e. I do not empty it ever).
2. I believe the pump is at the same level as the tank. The lines go straight back into the nether regions of the interior.
3. Thanks for the info about the longevity of pumps. At least that makes me more confident I'm not ruining it.

 

[NY_Dutch]

Just to tell you a bit about RV pump longevity, I got a panic call a few years ago from a fellow that had accidentally turned on his water pump with a dry tank while the RV was in storage with no shore power connection, but a fully charged battery. He didn't realize it had happened until he came back a few days later and found the battery was dead and hooked a charger up to it. The pump came on and he quickly shut it off, expecting it was ruined. He had called me to ask about a replacement. I suggested he add a few gallons of water to the tank and try the pump before giving up on it. The next call I got was from a very happy camper, and as far as I know that pump is still working just fine today.

 

[johntk]

Just to tell you a bit about RV pump longevity, I got a panic call a few years ago from a fellow that had accidentally turned on his water pump with a dry tank while the RV was in storage with no shore power connection, but a fully charged battery. He didn't realize it had happened until he came back a few days later and found the battery was dead and hooked a charger up to it. The pump came on and he quickly shut it off, expecting it was ruined. He had called me to ask about a replacement. I suggested he add a few gallons of water to the tank and try the pump before giving up on it. The next call I got was from a very happy camper, and as far as I know that pump is still working just fine today.

Great to hear this story. So many times I would run the pump for 20-30 seconds then let it 'cool down' for about the same length of time, then run it again. Kept doing this repeatedly until it finally primed and quit running. So glad I won't be doing that again!

 

[Rene T]

So in your original post you said it would take 3 to 5 minutes. Does that include every 30 seconds for the cool down. The next time, just let it run and see how long it takes. Please let us know the outcome.

 

[John From Detroit]

Just to tell you a bit about RV pump longevity, I got a panic call a few years ago from a fellow that had accidentally turned on his water pump with a dry tank while the RV was in storage with no shore power connection, but a fully charged battery.

Well the only difference between that story and mine
1: I have no idea how long the pump ran dry as I was on shore power and living in the RV...
2: I did not make the panic call.. Just filled the fresh tank

 

[Gary RV_Wizard]

Whatever it's doing, it's not "priming". It only takes maybe an ounce to fill the self-prime reservoir inside the pump. What you term "priming" is probably the pump filling the fresh water piping (Including the heater tank) and bringing the system up to operating pressure, usually about 45 psi. Typically the water lines hold about a gallon or so, so maybe 30-60 seconds of pumping unless the pump is having trouble sucking water from the tank.

Once the pump builds pressure and shuts off, does it ever cycle again without anybody opening a faucet? If so, there is a leak somewhere in the system, possible even within the pump itself.

 

[johntk]

Whatever it's doing, it's not "priming". It only takes maybe an ounce to fill the self-prime reservoir inside the pump. What you term "priming" is probably the pump filling the fresh water piping (Including the heater tank) and bringing the system up to operating pressure, usually about 45 psi. Typically the water lines hold about a gallon or so, so maybe 30-60 seconds of pumping unless the pump is having trouble sucking water from the tank.

Once the pump builds pressure and shuts off, does it ever cycle again without anybody opening a faucet? If so, there is a leak somewhere in the system, possible even within the pump itself.

The water lines are full. This happens when I turn off the shore water and turn on the pump. This is when it rachets for 5 minutes. It is not pumping water anywhere. Also once it primes it works great - does not run unless I open a faucet or flush. No leaks in the system.
I assume there is a problem sucking water from the tank even when it is full. Just not sure of the cause since it works so well once it is primed.

 

[johntk]

So in your original post you said it would take 3 to 5 minutes. Does that include every 30 seconds for the cool down. The next time, just let it run and see how long it takes. Please let us know the outcome.

Rene,
I answered your Post right after you sent it but looks like it didn't send back.
The 3-5 minutes is priming time only - not total time.
I will be away from the MH for a while but will let you know how it worked to just let it keep running.

Thanks,
John

 

[Gary RV_Wizard]

This is when it rachets for 5 minutes. It is not pumping water anywhere. Also once it primes it works great - does not run unless I open a faucet or flush. No leaks in the system.

Well, it's pumping something. It pumps as long as the water line pressure at the pump outlet is less than the pressure switch hreshold in the pump, roughly 45 psi. If there is a lot of air in the lines the pump may push water in until the air compresses and pressure builds.

 

[Ex-Calif]

Here's an experiment. Hook up city water first before the next trip. Turn on the faucets one at a time - hot and cold. If you see spitting it's a sign there is air in that supply.

Even if no air close the faucets and turn on the pump. If it doesn't run for 3 minutes. You know pretty much that the pump is just doing it's job and there is space in the system somewhere and the pump is just filling it up.

My kid ran the water tank dry and left the pump on. I was on shore power. That pump could have been running dry for days. Having red only a few posts here I expected doom and gloom. Pump has been working fine 5 months on.

I am wondering if there are any backflow check valves in the system. Intuitively I would think that the water would not reverse through the pump but all the supply lines except the toilet are higher than the tank so if back flow is possible it can happen. If a faucet drips under pressure, air can certainly go in under vacuum.

BTW - My pump always runs at least 30 seconds when I switch off city water. I just always thought it was normal. Minutes sounds like filling a water heater to me. Is the water heater drain dripping?