The way my boat came to me it had a single large pump in the bottom of the bilge. It had about 20 feet of 1 1/2" hose routed to the transom. The hose held enough water that when the pump stopped running the water would flow back to the bilge, lift the float switch, and restart the pump. It would actually pump that same couple gallons of water back and forth all day. Can't believe the PO left it that way. I fixed it by adding the smallest pump I could find (360gpm I think) with it's own switch, and routing it's 3/4" hose out the side of the boat with as short a length as possible. Doesn't hold enough water to restart the pump. While I was at it, I made a pedestal to raise the switch for the big pump about 3" from the bottom. The little pump handles any nusance water and the big pump hasn't run since. Didn't think of adding an alarm to it but it is a good idea.