Filling Fresh Water Tank

[Dobie dogs]

We just purchased a new three phase water treatment system and the pressure is greatly reduced (as expected). This forced us to fill the FWT using the power fill mode. My question is “why, while filling the tank and the pump is in the on position, does the pump continuously run?” It doesn’t make sense to me because i would think that the pressure would be maintained. Obviously not, but am I on the right track with my analysis?

Thanks

[rohrmann]

It runs because you aren't supposed to have the pump turned on while filling the fresh tank with the power fill. Turn off the pump, fill the tank, then turn the pump back on.

[Dobie dogs]

Thanks I worked that out. No where in the manual does it reference not to have the pump on while filling the tank. The pump should draw water from the tank whether or not it’s being filled. The tank is not under pressure. Hence the question why is the pump running while filling. It can be gravity fed while the pump is on so what does adjusting to the power fill do to cause the pump to run?

Thanks

[rohrmann]

When using the power fill, you are using the same hose that the pump draws water from the tank with. So, when pushing water into the tank with the Tank Fill valve in the tank fill position, you are depressurizing the water pump pressure switch by not having pressure and the pump runs trying to pump water. This is a drawing I made several years ago of the plumbing in our rig, and you can see when the water fill valve is switched from normally feeding water from the city source of the cold water system to the fill position, you are connecting city water directly towards the tank. The blue lines in the valves are normal flow.

[mazboy]

just turn the pump switch off.

[Dobie dogs]

Thanks very much that makes sense