The consensus in this forum seems to be that a second bilge pump should have its own discharge hole; one not shared with the pump already installed. There is somewhat less consensus as to the viability of a second pump depending on what you wish, or expect, it to do, e.g., keep the boat from sinking or do something less demanding. The question of a "high water" alarm has come up, but again--to what function other than to alert you that the lower bilge pump is not keeping up with the ingress of water. My bilge alarm is set very near the level of my centrifugal (impeller) pump, and there is no other electric bilge pump. There is a manual (diaphragm) one operated from the cockpit that also drains the bilge. It's also been noted that the rated discharge capacities of the centrifugal pumps are very misleading in that they do not consider the height that water must be raised for discharge, which affects the actual discharge rate, significantly so. A pump(s) that cannot actually move 3000 gal/hr out of the boat (50 gal/min) probably cannot save it if there is significant ingress. For example, a 1.5-inch-diameter hole one ft below your water line will admit about 44 gal/min of seawater. So, if your two pumps together cannot match that through separate discharge ports, then you may end up hearing your alarm, but also finding little that you can do about it, in the worst cases, except to get the raft ready to deploy!!
Well I didn't mention that above; but of course finding and stopping or slowing the leak, if possible to do so, should be one's first priority if there is time. To that end, I have aboard the wooden plug set, some spongy nerf-type balls that can be stuffed into various sized holes or cracks, a tube of that "mighty putty" that sets up and seals when wet, and a tarp of sunbrella which could be wrapped over a hole or crack in the hull from the outside of the boat, etc. I also have aboard a few bailing buckets and two shower sump pumps. The bow of the Bavaria is reinforced with Kevlar.
The consensus in this forum seems to be that a second bilge pump should have its own discharge hole; one not shared with the pump already installed. There is somewhat less consensus as to the viability of a second pump depending on what you wish, or expect, it to do, e.g., keep the boat from sinking or do something less demanding. The question of a "high water" alarm has come up, but again--to what function other than to alert you that the lower bilge pump is not keeping up with the ingress of water. My bilge alarm is set very near the level of my centrifugal (impeller) pump, and there is no other electric bilge pump. There is a manual (diaphragm) one operated from the cockpit that also drains the bilge. It's also been noted that the rated discharge capacities of the centrifugal pumps are very misleading in that they do not consider the height that water must be raised for discharge, which affects the actual discharge rate, significantly so. A pump(s) that cannot actually move 3000 gal/hr out of the boat (50 gal/min) probably cannot save it if there is significant ingress. For example, a 1.5-inch-diameter hole one ft below your water line will admit about 44 gal/min of seawater. So, if your two pumps together cannot match that through separate discharge ports, then you may end up hearing your alarm, but also finding little that you can do about it, in the worst cases, except to get the raft ready to deploy!!
