Fresh water tank fills unexpectedly

[zim390]

I own a 2004 Zeppelin 281-lwt and recently noticed that the fresh water tank is filling when connected to external water source. I am not aware of any valve being left open that might control this. Any ideas on what could be causing this? I did inadvertently hit the water pump button on while connected to water supply, could there be some kind of "check valve" stuck open in the water pump? Any insight would be appreciated.

[chuckster57]

There is a check valve in the water pump. The city water hooks up just past the water pump and that valve is meant to prevent any “back flow”. Your water pump may be failing and depending on brand you may be able to take it apart and fix it.

[zim390]

Thanks for the quick response. Do you know if the check valve opens when connected to external water and the pump is activated? Reason I'm asking is that I know that when I first connected to external water, the water pump switch was on and probably ran for several minutes before I noticed and shut it off. Could the fresh water tank had filled during this time that the pump was on and connected to external water?

[flybouy]

Thanks for the quick response. Do you know if the check valve opens when connected to external water and the pump is activated? Reason I'm asking is that I know that when I first connected to external water, the water pump switch was on and probably ran for several minutes before I noticed and shut it off. Could the fresh water tank had filled during this time that the pump was on and connected to external water?

Do you have a water regulator installed on the hose? If the water supply pressure is excessively high then I can see it overwhelming the pump's ability to keep the water from back flowing. Other thought, if it's the original pump then it's 16 years old so...

[zim390]

Yes.....I do have a water regulator on the water line coming into the trailer. It's currently set to 40 psi. I do believe its the original water pump

[JRTJH]

The "check valve" in Flojet pumps is a "rubber flap" that works in conjunction with the roller diaphragm to prevent the backflow of water through the pump to the tank. Typically, it fails when trash or bits of construction debris get into the pump head and prevent the rubber flap from laying flat against the roller diaphragm. That happens in "relatively new pumps with pliable rubber components. As rubber ages, it becomes brittle, the surface becomes cracked and rough. Your trailer is a 2004 model, so if this is the original water pump, it may simply have "worn out". If it's a newer pump, you might want to take it apart, clean the rubber diaphragms, coat them with a "food grade silicone pump lubricant" and reassemble the pump. If it works, great, if not, then you'll either need to install an "upstream check valve" or replace the pump head.

If it were me, if the pump is the "2004 original", I'd just spend the $60 and replace the entire pump.

[zim390]

Thanks for the info. You're right, I should probably bite the bullet and install a new pump. I still have the following question: If the trailer is connected to external water source and the water pump is turned on, will it automatically begin to fill the fresh water tank? Could not find answer in the owners manual.

[bobbecky]

No, if the check valve is working properly, the water will not backflow through the check valve. We were at a park years ago when our check valve failed and water was overflowing from the tank vent. We were no where near an RV dealer to be able to purchase a new pump, so I went into a small hardware store and bought a check valve that would fit the PEX plumbing, and cut it into the pressure side line to the pump and this solved the problem. I had to replace the pump several years later for a different issue, but just left the check valve in place and still have no problems. The check valve is the brass device in the photo. If you do not have a strainer on the tank side of the pump, whether you replace the pump or not, this would be an excellent time to install one. Also, do not install a check valve on the tank side of the pump as the fittings of the strainer can not handle the pressure and will leak.

[skids]

Try this, because it worked for me. Do not hook up city water and do have water in the fresh tank. Pump off. Turn on all valves. Turn on pump. With valves open it allows the maximum flow through the pump because of minimum resistance. This can wash out debris from the check valve. It worked for me and was effortless.

[Newk]

I had the same problem on a previous trailer. It also didn’t have a winterizing valve. I put one of those in and it solves the problem, while adding a new convenience!