I installed a Water Witch level switch on Impetuous. It is located in the valley just aft of the shower sump. Then I installed a check valve because the backflow from the through hull to the bilge was enough to restart the bilge pump. AND THEN, I had to drill a vent hole in the bilge pump outlet. Why?
Because the Water Witch comes on and stays on for 14 seconds. Which is about 5 seconds longer than the bilge pump needs to completely empty the bilge and pump air into the discharge hose. And the pump would vapor lock and not pump out the bilge the next time. The little hole in the discharge lets the air out so that the pump comes back on suction.
I also have a bilge pump light that is visible from the helm. Whenever I see it on, I start counting. As long as it goes off before I get to 15, everything is good. The last time it stayed on, a hose on the freshwater system came off it's fitting and we were pumping the water tanks into the bilge and then overboard. Root cause was owner error tightening the hose clamp.