The Worry-free Bilge Pump

Out of sight, out of mind, this critical pump needs more respect.


Due the lack of maintenance they receive from the average sailor, I often refer to bilge pumps as the Rodney Dangerfield of boat equipment, meaning they just don’t get no respect. Its a funny, but also troubling statement, particularly as bilge pumps are often the first and only line of defense against sinking.

bilge pump

Photos by Frank Lanier

Bilge Pump vs. Emergency Pump

First off, don’t confuse your bilge pump with an emergency pump, which provides much greater dewatering capacity. That being said, although their primary job is clearing incidental water from the bilges (packing gland drips, rain water, etc.) bilge pumps can provide crucial extra time when taking on water, allowing you to find the source of a leak, don lifejackets, or hopefully keep your boat afloat long enough for help to arrive. Its a mighty tall order for a fairly simple piece of equipment.

General Considerations

No amount of pumping capacity can overcome a bilge choked with trash and debris. The first step on the path to bilge pump nirvana is making sure your boats bilge is clean and free of trash and debris. Routine bilge cleaning is a fact of life for older boats, but even that new boat you’re purchasing can have a bilge littered with pump-clogging bits of construction material (wood shavings, screws, bits of fiberglass, gobs of epoxy, etc).

Oily bilge residue should also be cleaned up and disposed of properly. In addition to the ecological concerns of accidentally pumping it overboard, oil combines with dirt to form a gooey sludge that can clog pumps and prevent float switches from operating properly.

Use marine grade hose for pump discharge runs and secure them at each end with marine grade stainless steel hose clamps. Hoses should be routed as directly as possible to their discharge thru-hull and should also be properly supported (approximately every 18) to prevent chafe and excessive movement.

Speaking of discharge thru-hulls, they should be situated well above the waterline to prevent water from siphoning back into the bilge. Siphon breaks and riser loops are also recommended and should reach at least 18 inches above static waterline. This prevents back-siphoning.

Automatic float switches (if installed) must be securely mounted and installed clear of wires, hoses and other obstructions that can impede operation of the floating-arm or flapper type switch. Enclosed float switches eliminate this worry, but they’re sometimes difficult to inspect and test. Regardless of the type you choose, make sure each pump has a manual switch as well; none of the automatic systems is failsafe.

Maintenance tips

Problems with centrifugal pumps typically involve clogging, defective automatic float switches (if installed) or corroded electrical connections, a common problem with any electrical gear installed in corrosive environment of a vessel’s bilge.

Maintenance is generally limited to clearing the strainer (centrifugal pumps have one built into the base) and water proofing of all connectors. When it comes to repair, with the exception of the larger, rebuildable units, most centrifugal pumps are cheaper to replace than repair. The September 2010 (High Capacity Bilge Pump Test) and October 2010 (Low Capacity Bilge Pump Test)  issues identify our favorites.

Maintenance and repair of diaphragm pumps typically involves opening up the pump body, clearing the pump chamber of debris, and checking the diaphragm and valves for damage or deterioration. Other than clogging, most problems will be caused by torn or damaged check vales. The diaphragms can also fail, however they will typically outlast several valve changes. For long cruises, you’ll want to take spares.

Finally, check all hose runs for kinks, cracks, or splits. If you have a check valve installed (something that is not recommended due to the possibility of clogging and failure) make sure it is clear and operating properly.

Darrell Nicholson
Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 50 years. Supported entirely by subscribers, Practical Sailor accepts no advertising. Its independent tests are carried out by experienced sailors and marine industry professionals dedicated to providing objective evaluation and reporting about boats, gear, and the skills required to cross oceans. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser who has been director of Belvoir Media Group's marine division since 2005. He holds a U.S. Coast Guard 100-ton Master license, has logged tens of thousands of miles in three oceans, and has skippered everything from pilot boats to day charter cats. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida. You can reach him at


  1. this is all god information, however, I am looking to find PS opinion on the better bilge pump CONTROLLERS. ie, the electronic device or just plain switch & pilot lamps that turn on & MONITOR the electric bilge pumps i have in place, . Id like to know what CONTROLLER is better in PS testers opine, eh?