Water pump draws air at half full tank

[bottieri]

When my fresh water tank is half full (actually, not by gauge) the pump sucks air. I cannot draw water beyond a half full tank - then have to refill the tank. So, the usable fresh water supply is only half a tank rather than the whole storage capacity. Has anyone experienced this condition and if so what sis they find?

I assumed the pump pickup was at the bottom of the tank in the same line as the drain. Before i dive into the problem, any experience would be helpful.

[George Z]

The pump seal might be going bad. It pumps as long as the level of water is above the pump , but as soon as the water level is below the pump, and it must produce a vacuum to draw water, it sucks air through the seal or possibly a cracked line, or loose fitting.

George

[RV Wizard]

Look for signs of water stains. This might show you where your air leak is too! When the tank has enough pressure the loose fitting may weep and when pressure by volume decreases the pump now can suck air at a loose fitting. If you have a means to fill the tank from the city water connection, verify that you have the valve to do so closed when using the pump and that it too is not leaking by. Let us know what you find.

[TXiceman]

I'd look for a slight leak on the pump inlet. Tighten all of the connections to be sure.

Ken

[bottieri]

None of the symptoms listed above seem to be the problem, but I tightened the finger twist connectors on both sides of the pump. This is a brand new RV and the first time we took a trip with it, this condition showed up.

Also, the level guage reads 2/3 full all the time and I think the wires may be attached wrong.

Can someone tell me the color and positions of the four wires attached to the tank?

Thanks for all the help and suggestions!

[Flagelpater]

How do you know it draws air, what are the symptoms? The pump is outside the tank. Any leak in the supply line to the pump would show up even when the pump is not running. If the symptom is other than air bubbling out of the faucet I would check for a clogged pump inlet screen. Do you have good flow when it is working?

[bottieri]

This is a new RV! Air spurts come out of the faucets when the tank gets to about half full (or a little less).

However, upon closer inspection, I find that the pickup is at the same level as when it starts sucking air. So, my problem isn't a leak, but a poorly place pickup pipe. I guess splicing into the drain pipe would be the answer to being able to use more of the tank volume.

[cowboy2]

Quote:

Originally Posted by bottieri When my fresh water tank is half full (actually, not by gauge) the pump sucks air. I cannot draw water beyond a half full tank - then have to refill the tank. So, the usable fresh water supply is only half a tank rather than the whole storage capacity. Has anyone experienced this condition and if so what sis they find? I assumed the pump pickup was at the bottom of the tank in the same line as the drain. Before i dive into the problem, any experience would be helpful.

if u can get your hands on pump ,on the intake side of the pump there is conection that has a small inline filter ,this filter sometimes gets pluged or the fitting that conects to pump will come loose ,try this out first ,use air to kleen filter

[bottieri]

This problem is now resolved. Here's what I did to correct it:

The pump pickup pipe being almost half way up the tank was the cause. I cut that pipe and plugged it with a half inch OD brass nipple and capped the end. It is necessary to heat the blue plastic factory installed water pipe a little to soften it, to get the standard fittings to go into it. That was necessary at every connection. I of course, used clamps too.

I cut and spliced a tee in the drain line (which is at the bottom of the tank). It was necessary to install a ball valve between the tee and the drain cock as for some reason the cheap plastic drain cock allows air to be sucked in even when turned off. Regular clear plastic flexible pipe (hose) was used from the tee to the pump fitting. It is possible that this type of pipe could collapse under the pump suction if warm enough, but probably will be o.k. for such a short distance.

The pump intake is now teed off the drain pipe at the bottom of the tank and works perfectly.

[Flagelpater]

Glad to hear you got it fixed. Sounds like a major mistake during production. If you are in a situation where you need to winterize make sure your new plumbing setup does not have undrainable low spots, unless you use antifreeze. Thank you for reporting the fix.