Water pump won't shut off

[rayjones]

Hi. I have a 2015 33 with a jabsco par max 2.9 that will not turn off.
I have searched for any leaks and cannot find any, and I've checked as
the transom shower and no evidence of leaks at all. I've tried a new pressure
switch and a new pump and the problem persists
When the taps are off and the pump is on at the panel the pump pulses
suggesting that water is escaping somewhere.
I have resorted to turning off at the panel after every use
Does anyone have any suggestion.
Thanks in advance

[sy_Anniina]

Do you have at least semi-transparent expansion tank connected to the system on the pressurized side?

If so, I would suggest observing the water level in expansion tank to confirm if you have a leak on the pressurized side of the system.

My water pump has sometimes trouble priming and keeps cycling because of air entering the system from the pump-input side connections -> pump can not rise pressure until all air is bled out.

BR,

Tommi

[IslandAlchemy]

I would say that the most likely reason is that you have air in the system.

[tiger79]

If there are no leaks, the problem is the valves in the pump, which are allowing a slight seepage of pressurised water back into the pipe from the tank.  As this happens, the pressure in the system gradually drops and the pump operates for a second or two.

The solution is to replace the valves, you can buy a valve kit as a spare part.

[rayjones]

Thank you to you all.
With the exception of an expansion tank (not fitted on my boat) all good advice . Thanks

[Salty]

When you say you have no expansion tank, do you mean that you have no pressure accumulator fitted? If not is there some reason why?
My B36(2002) has a pressure accumulator fitted between the pump and the taps, and this stops the pump from continuously cycling. Unless there is some significant reason why you don't need a pressure accumulator, I would get one fitted sooner rather than later.

[tiger79]

When you say you have no expansion tank, do you mean that you have no pressure accumulator fitted? If not is there some reason why?
My B36(2002) has a pressure accumulator fitted between the pump and the taps, and this stops the pump from continuously cycling. Unless there is some significant reason why you don't need a pressure accumulator, I would get one fitted sooner rather than later.

An accumulator tank only dampens the pump operation.  Modern pumps don't need them.  The pump cycling the OP described is a consequence of valve leakage, and an accumulator tank wouldn't make any difference.

[Anthony]

they behave like this when the tank is empty; therefore top up both tanks or flick the control lever to the other tank and open a tap to clear any air