Getting Pumped

Emergency bilge pump options, installation and maintenance.

Frank Lanier Photos

Like flares and life jackets, emergency bilge pumps are a safety investment that boat owners hope they’ll never need. Many make light of the topic by quoting that old adage about the best emergency bilge pump being a frightened person with a bucket. But scared folks get tired too—long before whatever’s letting all that water in is fixed. Emergency pumps provide valuable time when taking on water, time that can be spent searching for and repairing a leak, donning life jackets or making a distress call. To keep passengers from having to choose between grabbing their life jackets or joining the bucket brigade, here’s some common sense advice on emergency bilge pump options, installation and maintenance.

Know your type
There are a number of choices when it comes to back-up pumps, from engine driven units to manual pumps. However, electric powered centrifugal pumps are probably the most common and are the focus of this article. They pump a lot of water, are relatively inexpensive and are designed to operate while completely submerged. They also have large internal tolerances and can pass small amounts of debris (a big plus for emergency pumps), but this does make them highly sensitive to vertical or static head—in other words, the higher they have to push water vertically, the less effective they become.
In addition to electrical pumps, you may want to consider having a large capacity manual pump on board. Though useful as back-ups, keep in mind they’re powered by elbow grease and even the fittest crewmember will have a hard time keeping up an effective pace after awhile… assuming you can even spare a crewman to man the pump in the first place.
Engine-driven emergency pumps allow you to harness the tremendous power of the engine in the event of hull breach. They can be powered off the crankshaft pulley (using a manual or electric clutch assembly) or drive train. Some designs, for example, mount directly to the engine shaft and as long as it’s turning, the pump is operating and starts working automatically in the event of an emergency. Pumps of this type can pump up to a whopping 24,000 gph.
Another option is installing a suction takeoff from the engine’s raw water pump. Just remember that running the engine pump when dry will damage the impeller, and that the intake connection should be in front of the sea strainer (so you don’t suck bilge debris into the engine). This is a proven and accepted pumping method, but know what you’re doing before you do it, otherwise you can seriously damage your engine.

Installation tips
Back-up pumps should be securely mounted and configured to automatically turn on when bilge water levels reach a predetermined height above the turn-on point for the primary pump (typically three to four inches, but low enough to prevent water from overflowing the bilge and damaging furnishings or equipment). This lets the smaller primary pump take care of normal seepage (with less battery drain) and leaves the larger pump to kick in only when needed. It also keeps the back-up pump from resting in the normal accumulation of bilge water where it can become clogged with sludge and debris, or seized from disuse.
Discharge thru-hulls should be situated well above the waterline to prevent water from siphoning back into the bilge. Siphon breaks and riser loops are also recommended but ensure they reach at least 18 inches above static waterline where possible. Use marine grade hose for pump discharge runs and double clamp all bilge pump hoses with marine grade stainless where possible.
Make sure all pumps, float switches and strainers are easily accessible, essential for routine maintenance and emergency repairs. Install “manual on” switches for each pump in addition to any automatic float switches that may be installed. That way, should the float switch fail, you can still activate the pump via the manual switch.
Provide appropriate circuit protection for each pump and ensure all electrical connections are located well above normal bilge water levels (to reduce corrosion issues) and properly terminated with marine grade connectors.
Finally, as many hull breaches occur at the dock (due to failed thru-hulls, hoses, and the like) it’s always a good idea to include a visual/audible high water bilge alarm as part of your emergency de-watering strategy. Alarms should be loud enough to be heard over engine noise while under way, and ideally by anyone passing by or marina personnel when docked. Installing a visual “bilge pump on” indicator at the helm for each electric bilge pump is also a good idea, one that can provide even earlier indications that something is amiss. A bilge pump on/off counter for primary bilge pumps is also desirable to indicate how often bilge pumps are cycling (making a leak more noticeable).