I also added a sensor (Water Witch) and Manual/Auto switch to the main bilge pump. Our boat is a very dry boat, but we do get water down the mast channel when we have a lot of rain. The existing Jabsco Diaphragm pump only runs on demand off a breaker in the main panel.
So I added a second switch at the pump that allows you to operate it manually, holding the switch over, or in Auto mode.
To the Auto side of the switch I connected a Water Witch electrical sensor. I tested the whole arrangement in a bucket to see that the pump comes on and shuts off after the water is pumped out. I left the switch in auto mode over night (during the rains from 'Bill') to see how much it would reduce the batteries. I have 4 house batteries with a total of 410 amp-hours when fully charged. Over a period of about 20 hours this setup used about 11 amp-hours. So I suspect I could leave this run for a week if needed. Of course, the pump draws a lot more when it runs, but it only takes about 30 seconds to pump out the 3" of water found by the sensor. The pump only draws about 6 amps when running so 6 amps for a minute or less does not produce much draw down.
So it was a busy week, but as I said I feel better prepared. And I got some sailing in also.