Water pump not priming

[Asheville]

I have a 2012 Interstate 3500. I used the water pump one or two times before for a short while and it worked fine. The last trip I took it would not work. The pump is running but no water comes through. Airstream support diagnosed it as the pump is not priming itself. They said since it is still under warranty I can just take it in and get it fixed or replaced at no charge. Problem is the nearest dealer is over 2 hours away. They suggested taking the pump apart to see if something is clogging the pump. Also suggested taking the screen out to see if it is plugged up.

Before I start taking things apart, has anyone else had this same problem? If so, what was the solution?

Thanks

[Protagonist]

Originally Posted by Asheville

I have a 2012 Interstate 3500. I used the water pump one or two times before for a short while and it worked fine. The last trip I took it would not work. The pump is running but no water comes through. Airstream support diagnosed it as the pump is not priming itself. They said since it is still under warranty I can just take it in and get it fixed or replaced at no charge. Problem is the nearest dealer is over 2 hours away. They suggested taking the pump apart to see if something is clogging the pump. Also suggested taking the screen out to see if it is plugged up.

Before I start taking things apart, has anyone else had this same problem? If so, what was the solution?

Thanks

Had that problem with mine. The nice folks at Airstream of Mississippi, AKA Foley RV Center, were able to prime it for me in just a couple of minutes without taking anything apart except to remove the bottom drawer so they could reach the pump. Not sure exactly what they did, though. Guess I should have set up a webcam or something so I could watch. There's no other way for two people (the mechanic and me) to see inside the drawer opening at the same time.

[Lily&Me]

Is it everything that won't run----shower and sink?

We have had reduced flow when sediment has clogged the filter, I would sure check and clean out that screen.

Also check and clean the little screen in your sink spigot.

If you had bad water, those screens can clog up quickly. Not a terribly big deal to remove and clean them. We have done it and are not terribly handy.


Maggie

[DaveFL]

New vehicle shouldn't have trash in line, try loosening closest fitting on the pressure side of the pump. it shows arrow or reads output. If I run out of water on the boat, the pump sucks air and then won't pump water, have also managed to open valve closest to the pump and with a full tank it will self prime. Make sure your tank is full or at least has a level above pump input.

[Asheville]

Will try that but I have no flow at all so that may not be the problem. Thanks

[Asheville]

Airstream suggested I fill tank to over flowing which i did and it still would not pump water ( although pump was running). I will try loosening valve. When you say pressure side do you mean the incoming or outgoing side? Thanks

[Protagonist]

Originally Posted by Asheville

Airstream suggested I fill tank to over flowing which i did and it still would not pump water ( although pump was running). I will try loosening valve. When you say pressure side do you mean the incoming or outgoing side? Thanks

Pressure side is the outgoing side. Suction side is the tank side.

A sudden thought… The pump is supposed to be self-priming, but it won't pump against air pressure, and that may be what's preventing it from priming. Open ALL the faucets, about midway between hot and cold, THEN turn on the pump. With an outlet for air to escape, the pump may prime itself.

If that doesn't work, THEN try disconnecting the pressure side.

[Lothlorian]

I had this problem and had a RV tech check it out. He had a theory before he looked at it and went to the problem immediately. There was a very small amount of air entering in water tank side and he put plumber tape on the fitting and reattached it. I never have a problem since.

Brian

[ventport]

Like was said above, make sure the faucets are open when trying to prime the pump, so the pump is not pushing against an air cushion.

[mjayjensen]

A pluged discharge line. A failed pump. Most likely sucking air through the inlet line.
Jay

[73shark]

After refilling the tank last spring, I had to use compressed air to get it to prime. Stuck the air line in the fill port and wrapped a rag around it and press and released the air nozzle several times. The faucet were open. This was what my dealer recommended and it worked.

[Asheville]

Airstream suggested this also. I will try this before taking anything apart. Thanks

[wayneskid]

I had the same problem. Jim P. at Airstream CS suggested SLIGHTLY pressurizing the tank with an air compressor. This got it going right away!

[jquayle]

Same problem.

Dealer told me I needed the water level completely full, but that didn't help. They got it primed and advised they had found a lot of plastic shaving in the line.

Drained all the water during a ski trip to Tahoe to prevent water freezing in the lines. After I filled it back up it wouldn't prime.

Dealer walked me through checking the filter screen (most plastic shavings, but removing them didn't help)

I was able to get it primed by messing with the drain valves open and closed until it eventually primed. Overall I'm not thrilled with the performance of this units ability to 'self prime'.

Pressuring the tank as recommended in other posts may work great, but that's not really 'self priming' either.

[Protagonist]

Originally Posted by jquayle

Same problem.

Dealer told me I needed the water level completely full, but that didn't help. They got it primed and advised they had found a lot of plastic shaving in the line.

Drained all the water during a ski trip to Tahoe to prevent water freezing in the lines. After I filled it back up it wouldn't prime.

Dealer walked me through checking the filter screen (most plastic shavings, but removing them didn't help)

I was able to get it primed by messing with the drain valves open and closed until it eventually primed. Overall I'm not thrilled with the performance of this units ability to 'self prime'.

Pressuring the tank as recommended in other posts may work great, but that's not really 'self priming' either.

Before giving up on self-priming, next time, try this…
Fill the fresh tank brim full. If it's full, the pump doesn't have to lift the water as far.
Open every faucet, about halfway between hot and cold, to let any trapped air between pump and faucets bleed out of the lines.
The pump will not prime if it's pumping against back-pressure created by trapped air.
Then turn on the pump. If water isn't running in about 30 seconds, shut off the pump to avoid damaging it.
If that doesn't work, then add air pressure to the freshwater tank and try again.

[jquayle]

Good tip.

So just the 2 sinks, correct? You don't have to mess with the dump valves?

[Protagonist]

Originally Posted by jquayle

Good tip.

So just the 2 sinks, correct? You don't have to mess with the dump valves?

Two sinks and the toilet. One foot on the toilet foot lever, partway, like you're filling the bowl.

I think you mean the low-point drains. But no, if the faucets are open, the low point drains shouldn't need to be open as well. Opening the low point drains does the same thing as opening the faucets, but the faucets are just easier; with the bathroom door open you can reach everything from right there near the pump switch.

[dlb435]

The most common cause of the pump failing to prime is a loose filter bowl. Look at the pump and you will see a clear bowl with a metal strainer inside. The bowl unscrews to dump any trash inside and lets you clean the filter. Do this.
Check the rubber seal to be sure it is not cut or deformed. Put the bowl back on and see if it will prime. (try leaving on faucet open until water flows) Be sure that you do not have city water on. Be sure you have water in the fresh water tank.
As the pump runs, you should see water flowing in the filter bowl. If you get a mix or water and air then the filter bowl is not on correctly or the water inlet is either broken or not positioned at the bottom of the tank.

[TG Twinkie]

How far from the tank is the pump?
I frequently have to prime the pump in our coach. The water line including the inline strainer is only about 18" long.
Even when I open the faucets it won't prime. I use to disconnect the discharge hose at the pump, then run the pump until a little water comes out. Then it would be fine for days.
It seems to get an air bubble in the pump, especially after traveling with less than 3/4 tank.
I installed a 2 way valve (which is in a tee) in the discharge line of the pump. If you can picture the letter tee (upper case). The pump line is connected to one end of the top of the tee, the other end of the top of the tee is to the water supply line to the coach. The leg of the tee goes to a drain line.
When it won't prime, I just turn the handle on the tee until water goes out the drain line and the pump sounds like it is working. Then turn the handle back to the original position and everything is fine.
The pump is the original (39 years) so it may be on it's last days. But has been working fine once primed for over 3 years.
The biggest problem I have is the location of the pump. It's under the dinette seat. A minor inconvenience.

[Protagonist]

Originally Posted by TG Twinkie

How far from the tank is the pump?
I frequently have to prime the pump in our coach. The water line including the inline strainer is only about 18" long.

In the Interstates we're discussing, the pump is directly above the fresh tank, at floor level under the galley.