Fresh tank pump won’t draw water but works from winterizing line

[Moho81]

This is a new one to me and I will try to explain it best I can. This is not my RV but my In-Laws Wildwood FSX 17bhs.

We where camping together last weekend at a State Park with no water hookups only a place to fill the fresh water tank. They camped once this season prior to this trip and had water at the site so they did not use the fresh water tank or the pump and everything worked as it should. On this trip once set up they turned the pump on and it would not shut off and would only run water through the faucets in spurts.

I got called over to check things out and immediately found that they left the RV antifreeze line open so the pump was sucking in air through that. Closed that line off and purge the lines of air and it seemed that everything was good and the pump shut off. The next time the used the water they got a bunch of air again and the pump ran continuously.

I went back in and used the RV antifreeze line and my water jug to prime the pump in hopes to push the air through the pipes. This worked and the pump pressurized the system and we where able to have water run without issue off the water jug and antifreeze line but as soon as we shut the valve for the antifreeze line the pump would not pull water from the tank.

I trouble shot as much as I could with the tools that I had and did not find anything obviously wrong. Fresh water tank was filled, in and out connections on the pump where tight, low drain line caps also tight, all valves for the hot water tank and antifreeze lines where in the proper configuration, no onboard switch to control water from the tank just the switch to turn the pump on and no visible water leakage from any of the water pipes.

Any one have any suggestions as to what to look for next? With the limited cell service we had I had found something about making sure the check valve for the city water connection was properly seated unfortunately the check valve must be more internal past the hose connection and screen and I did not want to take that all apart at the campground just in case I needed something I didn't have to get it all back together again.

 

[Kirk]

I had found something about making sure the check valve for the city water connection was properly seated unfortunately the check valve must be more internal past the hose connection

What that refers to is the city water connection as it has a check valve to prevent the water from the pump from exiting out of the place where the hose would be if you had city water connected. If that was the problem you would see water coming out of the fitting where you connect a hose to supply city water. I am sure someone would have noticed.

Is it safe to assume that you actually observed that they had the freshwater tank full? It doesn't sound like it was. If it worked properly drawing from your water jug, but not from the tank, then the valve selecting the tank or jug connection could cause the problem or an empty tank could. But there isn't much else that is located before the pump.

 

[Mark_K5LXP]

At least on mine, the pump is gravity fed from the fresh tank. It would take just a minute to take the inlet fitting off the pump and verify in an immediate and conclusive way if there was an availability issue from the tank.

Mark B.
Albuquerque, NM

 

[Moho81]

What that refers to is the city water connection as it has a check valve to prevent the water from the pump from exiting out of the place where the hose would be if you had city water connected. If that was the problem you would see water coming out of the fitting where you connect a hose to supply city water. I am sure someone would have noticed.
View attachment 2477709
Is it safe to assume that you actually observed that they had the freshwater tank full? It doesn't sound like it was. If it worked properly drawing from your water jug, but not from the tank, then the valve selecting the tank or jug connection could cause the problem or an empty tank could. But there isn't much else that is located before the pump.
View attachment 2477722

I walked around the RV while the pump was trying to work and did not observe water coming out of the city water connection or leaking from the belly to indicate they had a broken pipe somewhere.

If the check valve was stuck open would the system still pressurize from the water jug? Thinking about it now wouldn't the water jug have the same issue if it was the check valve?

While I did not watch them fill the fresh water tank I did ask them what connection they used to fill and how long they filled the tank for. They correctly filled at the fresh water fill and they said it was probably between 5-10 for the tank to fill. I also took the cap off the fresh water drain to verify water was in the tank and judging by the force the water came out the tank was full enough that it should have been working.

 

[Kirk]

If it had been that check valve, there would have been water from the city connection anytime that the water pump was operating, no matter what the source of water was.

 

[Kirk]

. I also took the cap off the fresh water drain to verify water was in the tank and judging by the force the water came out the tank was full enough that it should have been working.

You are better than me if you can tell how full a tank is by the water coming out. There should be tank level indicators inside that would be better and best is to actually look at the tank as all that I am familiar with are translucent and with reasonable light you can easily see how much water is in the tank. Most tanks have a suction for the pump that is mounted at least 1 1/2 inches above the bottom of the tank and it typically needs to have at least 4 to 6 inches of water in the tank to be sure no air can be drawn by the pump.

they said it was probably between 5-10 for the tank to fill.

I very much doubt that the tank was full or very close to it, but to actually know we need to know the flow rate of the water supply.

 

[Moho81]

At least on mine, the pump is gravity fed from the fresh tank. It would take just a minute to take the inlet fitting off the pump and verify in an immediate and conclusive way if there was an availability issue from the tank.

Mark B.
Albuquerque, NM

I only checked that the connections where tight at the campground. I didn't want to disconnect them completely at the campground but certainly can back at there house.

You are better than me if you can tell how full a tank is by the water coming out. There should be tank level indicators inside that would be better and best is to actually look at the tank as all that I am familiar with are translucent and with reasonable light you can easily see how much water is in the tank. Most tanks have a suction for the pump that is mounted at least 1 1/2 inches above the bottom of the tank and it typically needs to have at least 4 to 6 inches of water in the tank to be sure no air can be drawn by the pump.

I very much doubt that the tank was full or very close to it, but to actually know we need to know the flow rate of the water supply.

True on both accounts while I know that the tank was not empty I know it had water in it still. I guess it's entirely possible that the level of the water inside the tank was below the line for the pump and I was taking there word for it that they filled the tank for 5-10 min and water did come out of the overflow to signal that the tank was full. Sorry I did not have that detail in the origional post.

Hindsight I should have used my water jug to fill the fresh water tank with 6-12 gallons of water to see what would happen.

 

[Gary RV_Wizard]

At least on mine, the pump is gravity fed from the fresh tank. It would take just a minute to take the inlet fitting off the pump and verify in an immediate and conclusive way if there was an availability issue from the tank.

Mark B.
Albuquerque, NM

I think a gravity feed from tank to pump is not a common thing. None of my 5 trailers or motorhomes had one, but some were more-or-less on the same level and so water might flow if the tank was full, but probably not if less than 1/4-1/2.

 

[Brad Buchanan]

This is a new one to me and I will try to explain it best I can. This is not my RV but my In-Laws Wildwood FSX 17bhs.

We where camping together last weekend at a State Park with no water hookups only a place to fill the fresh water tank. They camped once this season prior to this trip and had water at the site so they did not use the fresh water tank or the pump and everything worked as it should. On this trip once set up they turned the pump on and it would not shut off and would only run water through the faucets in spurts.

I got called over to check things out and immediately found that they left the RV antifreeze line open so the pump was sucking in air through that. Closed that line off and purge the lines of air and it seemed that everything was good and the pump shut off. The next time the used the water they got a bunch of air again and the pump ran continuously.

I went back in and used the RV antifreeze line and my water jug to prime the pump in hopes to push the air through the pipes. This worked and the pump pressurized the system and we where able to have water run without issue off the water jug and antifreeze line but as soon as we shut the valve for the antifreeze line the pump would not pull water from the tank.

I trouble shot as much as I could with the tools that I had and did not find anything obviously wrong. Fresh water tank was filled, in and out connections on the pump where tight, low drain line caps also tight, all valves for the hot water tank and antifreeze lines where in the proper configuration, no onboard switch to control water from the tank just the switch to turn the pump on and no visible water leakage from any of the water pipes.

Any one have any suggestions as to what to look for next? With the limited cell service we had I had found something about making sure the check valve for the city water connection was properly seated unfortunately the check valve must be more internal past the hose connection and screen and I did not want to take that all apart at the campground just in case I needed something I didn't have to get it all back together again.

Don't know if it will help but on our bus if you leave the valve in the city water fill position the pump will just move water around in a circle and not to the system.

 

[gwinger]

If the pump draws water from the winterizing hose with no problem, there may be a leak somewhere in the suction hose from the tank.

 

[Kirk]

I think a gravity feed from tank to pump is not a common thing. None of my 5 trailers or motorhomes had one,

So how did your water pumps get a supply? On all RVs that I have ever dealt with the water pump it was mounted to the floor near the water tank with a connection to the tank very near the bottom of the tank such that anytime there was a significant amount of water in the tank, gravity caused water to enter the suction line and if that line was removed from the pump the water would run out. In more recent models there is also a selector valve between the pump and the water tank to select pump suction either from the tank or from a line to put into a container for winterizing. From the decryption by Moho81, it seems his pump can draw water from the winterizing connection so if the tank has enough water to cover the connection to the tank, it should be able to draw from it since there would be little air between the valve and the tank than to draw water from the jug.

 

[gwinger]

So how did your water pumps get a supply? On all RVs that I have ever dealt with the water pump it was mounted to the floor near the water tank with a connection to the tank very near the bottom of the tank such that anytime there was a significant amount of water in the tank, gravity caused water to enter the suction line and if that line was removed from the pump the water would run out. In more recent models there is also a selector valve between the pump and the water tank to select pump suction either from the tank or from a line to put into a container for winterizing. From the decryption by Moho81, it seems his pump can draw water from the winterizing connection so if the tank has enough water to cover the connection to the tank, it should be able to draw from it since there would be little air between the valve and the tank than to draw water from the jug.

The OP has a travel trailer, not a MH.
Most TT's have the tank mounted under the floor and the pump above the floor.
No way gravity can feed the water up hill.
Mine has a suction hose about 5 feet long running uphill to the pump.
Only once did I have a problem. The connection on the inline filter was a little loose and the pump would not prime.

 

[Gary RV_Wizard]

So how did your water pumps get a supply?

Suction. It's what pumps are designed to do. It's how water gets drawn from wells or lakes. Part of a pump's spec is the distance it can lift water via suction.

 

[Kirk]

Most TT's have the tank mounted under the floor and the pump above the floor.
No way gravity can feed the water up hill.

That would be true if the tank is below the floor. None of the travel trailers that we have had were that way. All of ours had the water tank under the bed, but you are right and I really had not thought of that location but probably should have.

 

[gwinger]

That would be true if the tank is below the floor. None of the travel trailers that we have had were that way. All of ours had the water tank under the bed, but you are right and I really had not thought of that location but probably should have.

I said "most" are under the floor. I have owned three and all were under the floor.
Maybe the 5vers, or high end TT's have them inside.

 

[Gary RV_Wizard]

That would be true if the tank is below the floor. None of the travel trailers that we have had were that way. All of ours had the water tank under the bed, but you are right and I really had not thought of that location but probably should have.

Simply put, the RV builder mounts the fresh tank & pump where ever there is some space and is convenient for the assembly line workers to install. Either may be above or below the floor. I've owned or seen just about all the possible combinations of pump & tank locations. All 3 class A's I owned had the tank below floor level, but the pump locations varied. Ditto for one of the 5W, but the other had both tank & pump above the floor (under the dinette seat).

 

[Moho81]

I was hoping to get over to there house this weekend to see if I could figure out the problem but with a busy holiday weekend I never got a chance.

I have a couple of things I want to look at now and I also have a theory as to what caused this issues now that I have had a long time to think of it.

 

[Kirk]

All 3 class A's I owned had the tank below floor level, but the pump locations varied. Ditto for one of the 5W, but the other had both tank & pump above the floor (under the dinette seat).

If the pump is supplying water from a jug but not from the tank, then the problem has to be between the pump and the water tank, no matter where the pump is located.

 

[Moho81]

If the pump is supplying water from a jug but not from the tank, then the problem has to be between the pump and the water tank, no matter where the pump is located.

Agreed

 

[Gary RV_Wizard]

If the pump is supplying water from a jug but not from the tank, then the problem has to be between the pump and the water tank, no matter where the pump is located.

Agree.