Dumb Question

[mjlaupp]

Bill,

If there is water in the fresh tank, the city water is hooked up, the check valve is closed and you turn the pump on then one of two things will happen:
1) If the city water pressure is lower than the pump pressure then the pump will force water past the check valve. When the system is pressurized to the pump pressure setting the pump will shut off
2) If the city water pressure is higher than the pump pressure then the pump will shut off as soon as it has pressurized the pipe. In either case there should be no damage.

The damage would occur if the water pump is run when there is no water in the fresh tank. It would never sense high pressure and shut off and would most probably die due to overheating of the pump.

Mike

[Bill]

You're right, Mike. The pressure switch should turn it off before the cycle has gone very far. In my mind, question remains as to whether it will turn it off before the first cycle, and whether the first cycle busts the diaphragm. I don't know the answer.

As for pump overheat, I'm not sure that the pump is cooled by the water flow. And Shur-Flo says that the pump is protected by an overheat switch, so either way it seems unlikely. So at the end of the day (as the politicos say), I don't know for sure why it would fail.

Bill

[ShrimpBurrito]

I can tell you from experience that when you apply 75 psi of water pressure to the city water connection, the pump will run, and will run for at least a minute.

I seem to recall reading somewhere that, under normal operating conditions, the Shurflo pump turns off around 35-40 psi.

Dave

You can't check the pump by putting a little water in the tank. There is about an inch from the bottom of the tank and the outlet filter/outlet. Make sure you have several inches before you turn on the pump or it will not shut off as it can not build pressure.