On my last boat, I had exactly the scenario you suggest happen: a hose let go while I was away from the boat, the entire water supply was pumped into the bilge, and the pump's diaphragm failed.

I recently had to replace the pressure switch on our SM's AMFA water pump, which is a standard Square D switch.  Rather than exact replacement, I used the FSG2J24M4BP, which has a low-pressure cut off.  If a hose lets go, the pressure drops to such an extent that the pump will turn off and not turn on again until you manually flip the switch.  This should prevent the worst of this type of problem, but it won't protect against slow leaks.

Thanks,

Ryan and Kelly

SM 233 Iteration

Boston, MA, USA

On Mon, May 11, 2020 at 8:04 AM Arlo <svplanb@...> wrote:

On my last vessel  51 footer I used wall mounted timer from.McMaster carr that you could turn the dial from 15 to 120 minutes and then it would open the contacts electrically thereby turning off the water pump electric. It was placed by the galley sink. It worked flawlessly with daily use for 10 years. The reason we installed it was to ensure when we left the vessel that the water was turned off. On my Mango my SOP is simply turn off the water when I leave the boat. We have a bilge alarm when the water gets high for when we are onboard.