Fresh water tank filling on city water

[MrEnto]

Originally Posted by bobbecky

If the internal check valve is leaking and the pump otherwise works fine, adding an inline check valve on the pressure side of the pump will solve the problem. I did this years ago and it worked perfectly. I had to replace the pump some years later but the check valve is still in place and does not restrict water flow. It is the brass fitting near the lower center of the photo and is a Sharkbite type fitting.

I would think you should put it on the in-line not pressure side. I’m going through this same issue and my pump cycles periodically and I surmise it’s from the check valve leaking pressure back into the fresh tank. I have the valve and plan to put on the inlet side to solve both the issue of leak down and the city water filling my tank.

[JRTJH]

Originally Posted by MrEnto

I would think you should put it on the in-line not pressure side. I’m going through this same issue and my pump cycles periodically and I surmise it’s from the check valve leaking pressure back into the fresh tank. I have the valve and plan to put on the inlet side to solve both the issue of leak down and the city water filling my tank.

Depending on the actual installation of the pump, water tank and the routing of the input hose, installing any valve in that hose introduces a risk of creating an air leak that prevents the pump from priming. Additionally, depending on the individual components and how they are located, the pump head may not be able to overcome the restrictions in the input line to prime the pump. In other words, the pump may not have enough suction to draw water up to the pump head with the valve between the tank and the pump inlet fitting.

Theoretically, yes it'll work, in actual practice, why take the chance of cutting the supply hose, finding out it won't work and then having to risk the air leaks from what you cut?????

[rlh1957]

One common problem is back-flow valve on pump gets stuck.
If you connected city water and the water pump was on the back flow valve gets stuck open and water will back flow to the FW tank.

Turn pump off.
Turn off the city water, then open sink valves to depressurize the system.
Turn pump back on.
When it pressurizes system and shuts off, open a sink valve on cold and hot. Pump should cycle and water flows.

Then turn pump off and reconnect city water and turn on.
Back-flow valve should have been reseated and water isn’t filling FW tank anymore.

There are some RV’s with diverter valves that allow filling FW tank from the city water connection.
Make sure your diverter and by-pass valves are set correctly.

Rule of thumb is never have FW pump on when connected to city water.

[Jason.rhodes86]

I’ve never had the pump on while hooked to city wayer. I will try de pressurizing just to see if that helps. We are going on a trip next week so when I get back I plan on pulling the pump and looking to see if there is plastic shavings in it. That could make the pump cycle and also might have the check valve open. If that doesn’t work I’ll replace the pump and go from there.

[bobbecky]

Originally Posted by MrEnto

I would think you should put it on the in-line not pressure side. I’m going through this same issue and my pump cycles periodically and I surmise it’s from the check valve leaking pressure back into the fresh tank. I have the valve and plan to put on the inlet side to solve both the issue of leak down and the city water filling my tank.

The problem with putting the check valve on the suction side of the pump is the water connection from the tank is not capable of pressure and will leak. This is from experience. In the photo, notice in the background behind the brass check valve is a white coupling connector where the check valve was originally installed. This caused the fitting on the suction side of the pump to leak, and reading the instructions for the screen device attached to the suction side of the pump, it says this device is not supposed to be installed where water pressure is present. I would not install the check valve on the suction side, but if you do, you will know why it starts leaking when it does.

[Jason.rhodes86]

Took pump out and cleaned the pump head assembly. Unfortunately that didn’t solve the issue. Water still fills into fresh water tank and then when using tank the pump cycles on and off nonstop. So looks like I’ll try a new pump next see if that fixes it

[Dean260]

Hey all, thanks for the helpful thread. I am experiencing the same problem with retro flow into the FW tank. I'll try the recommended fixes and see if that solves it.

[Jason.rhodes86]

Got new pump as it was under warranty still. Waiting on camper to ge back from dealer getting soemtning else fixed. I’ll replace and hopefully that fixes the problem. I think In the future even on full hookups I’ll just use water tank and pump and refill as needed to avoid any issues going back and forth

[bobbecky]

On our Shurflo pump, the check valve is externally mounted and can be replaced independent of the pump diaphragm assembly. I'm not sure of other brands, only the Shurflo brand. https://www.ebay.com/p/659266671

[Jason.rhodes86]

Originally Posted by bobbecky

On our Shurflo pump, the check valve is externally mounted and can be replaced independent of the pump diaphragm assembly. I'm not sure of other brands, only the Shurflo brand. https://www.ebay.com/p/659266671

Mine is a flojet by xylem. There is no external check valve, at least that I saw.

[flybouy]

Originally Posted by Jason.rhodes86

Mine is a flojet by xylem. There is no external check valve, at least that I saw.

They have it built in. They are easy to disassemble and easy to remove the water lines. I would turn the city water off, open a faucet to relieve pressure, the remove the intake hose. Turn on the city water and have something handy to catch the water should it emerge. If water exits the intake side of the pump you found your problem, if no water comes out then put the hose back on ( recommend adding a strainer) and move on to the diverter valve.