Backup Bilge Pumps

One cruisers successful setup for a backup pump.

high loop and check valve

If I ever discover seawater sloshing around my cabin floor, I cannot be sidetracked by the need to operate a manual bilge pump; I need to be free to search for the leak and correct it. A reliable, high-capacity, electric bilge pump, reserved just for emergencies, is a necessity.

On board our boat, Brick House, a Valiant 40, we mounted the backup pump in the extreme forward bilge area, which never gets wet in normal conditions but would certainly be flooded about the time the floorboards started to float. In fact, a manual bilge pump was once located there.

In this small, dry area, we installed the largest, most powerful electric submersible pump that would fit into the space. We were not willing to give up valuable storage space in a locker, so we did not install a remotely mounted diaphragm pump. For other sailors, however, this could be a good option because the pickup hose and float switch could be set anywhere in the bilge. We installed the pump with its own dedicated, oversized electrical wire direct to the house battery, with a float switch and an in-line fuse. In the same circuit, we added a loud chirping alarm that sounds like a frightened canary.

When the pump is operating, this alarm will alert the crew to flooding. To prevent this alarm from adding to the excitement and difficulty of communicating in a bad situation, the alarm can be manually silenced with a switch at the nav station.

The discharge hose for this pump is routed with a high loop and discharges just below the sidedeck and well forward on the boat. Unless the pump is operating to blow seawater back out, heeling over and slamming into high waves could still force seawater back into the bilge. To avoid this, we installed a check valve near the discharge through-hull.

The problem with mounting this pump and its float switch was the lack of space. The pump and float switch could not be screwed to the floor, as is tradition. Instead, the pump had to be secured from the top. We cut a ring from a 4-inch PVC pipe to fit over the top of the pump, and then glued and screwed a plank of PVC to the ring. The ends of the plank were cut to fit between the forward and aft hull frames and were then secured. The float switch was mounted on a PVC shelf 4 inches higher than the base of the pump. This shelf was secured to the forward-most frame.

Electric bilge pumps

Even a set of electric pumps may not keep our feet dry, however. If we need additional pumping or the batteries fail, then we rely on our very high-capacity, manually operated Edson pump.

Mounted just inside the hanging locker at the bottom of the companionway, the Edson is as strong and powerful as it looks. It moves slightly less than one gallon of water per stroke through the 1-inch hose, which is the largest diameter hose we could thread through our boat. Connect a 2-inch hose, and the capacity is one gallon per stroke. The Edson is such a powerful sucker, it can throw all but the largest stick through its system. Still, it is best to fasten a large mesh screen or insert a bolt across the hose at the pick-up end.

The hose for this pump was originally installed so that it discharged directly out the starboard side of the boat in such a manner that when the boat was heeled, seawater could naturally drain back into the boat. A high loop and check valve were added to the discharge hose. Knowledgeable sailors may disagree with installing a check valve in a bilge pump line, as it could clog, but the check valve we used could not be a better one. It is an Edson check valve with a sight glass, so it is obvious if any debris is building up in the valve.

To make sure all limber holes and pumps run freely as we modify our boat, we always have a vacuum cleaner close by. Everything-all sawdust and dropped screws-is cleaned up. Before any passage, we degrease and scrub the scum and dirt from the main bilge pump sump and clean obvious dirt from the rest of the bilge. You would not want to drink from our bilge, but it at least is clear of any troublesome debris.

Patrick Childress
The late Patrick Childress, a longtime contributor to Practical Sailor, is a circumnavigator whose blog and YouTube channel is maintained by his widow, sailing writer and offshore sailor Rebecca Childress. You can follow Patrick and Rebecca's adventures aboard their Valiant 40 Brick House at


  1. This sounds good – I recently had to transit a new (to me) boat from Boston to the Chesapeake. All 9 seacocks were frozen open and the shaft seal was past its recommended replacement date. In addition to acquiring all the wood and foam plugs necessary to plug every thru hull I bought a 120 VAC trash pump, sized to fit into the bilge, and a gas generator with enough fuel to run full tilt for 24 hours. I calcualted the rate of incoming sea water for each through hull based on its diameter, depth, and an estimated discharge coef., and the annular space of the shaft where it passes through the stern tube. I selected a trash pump capacity to keep the boat afloat with any two through hull failures, using the pump performance curves to account for pressure head to lift water from the bilge, over the coaming, and friction losses. We made the transit without incident. After we arrived, I had the boat hauled and repared all seacocks and replaced the shaft seal. I had originally intended to return the trash pump – but I thought again and kept it. My subsequent analysis shows that just about every 12 volt DC bilge pump is woefully inadequate to really keep up with even one failed through hull fitting when one fully considers head losses in piping, fittings, check valves, and vertical lift.

  2. I have been unable to find the check valve you mentioned on the Edson website. I had never heard of one that fits your description. Can you supply more information on it so that I can source one?

    BTW, we used to own V40 #179, Coyote Moon, and presently own V42 #164, Blue Manx. Great boats!

  3. Ever since holing my Krogen 42, I too travel with a high capacity trash pump. Mine is driven by a small Honda engine. It is inconvenient to store the 2″ intake hose. Once you have seen your lower deck covered with water, you will figure out where to store it.