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Old 05-20-1999
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Bilge Pumps:First and Last Lines of Defense

Maintaining hull and deck integrity is always a boat keeper's primary objective. Keeping the water on the outside involves constant vigilance of the hull structure and its associated fittings.

Regardless of the skill and effort brought to maintaining a watertight hull and deck, however, accidents and mechanical failures occur that allow water to pour in. Sailors must be able to rely on their bilge pumps as the first line of defense.

Manual pumps
Piston Pump Every boat should have at least one manual bilge pump on board. Very small daysailers may have nothing more than a bailer or a bucket and well-muscled crew. Larger daysailers and pocket cruisers might get by with a piston-type pump, often called a lift pump or Navy pump, that is permanently installed.

Boats more than 20 feet overall should have, as a fundamental item of safety gear, a manual diaphragm bilge pump that is permanently installed. These pumps are available as 5-gallons-per-minute workhorses, on up over-40-gallons-per-minute gushers. Smaller-sized housings are made of plastic, while large units have aluminum or even bronze housings. Here are some considerations on manual pumps.

  • Every pump intake should have a strainer, sometimes called a strum box, so those bits of bilge debris cannot plug the intake hose. If the bilge is deep, a light line tied to the strainer makes pulling it for easy removal and cleaning.

  • If the pump handle cannot be left in the pump, it should be tied on or mounted in an obvious place nearby so it can be reached in an emergency.Diaphragm Pumps

  • While diaphragm pumps are extremely reliable, a set of spare valves and a spare diaphragm should be on board. Take the pumps apart to ensure that in a panic situation you'll know how to install replacement parts.

  • The pump should be located so that it can be used from the cockpit without having to open a locker or hatch that might let more water in. This usually requires an under-deck mounting kit with a bellows or gasket preventing water intrusion at the handle.

  • If two manual bilge pumps are mounted, the second one should be below decks.

Fitted with two suction hoses and a Y-valve, a single manual pump can empty two sumps. Alternatively, two pumps can empty to one through-hull if T-ed together; although if used at the same time, they will not be 100 percent effective.

Electric pumps
Larger sailboats generally have one or more electric bilge pumps on board. The most common are immersion pumps; however, motor-driven diaphragm pumps and rotary-impeller pumps are also available for this purpose. When wired to a double-throw switch and then a float switch, the operator has a choice of "off/manual/automatic." Here are some thoughts:

  • Electric bilge pumps should be wired through a dedicated fuse directly to the battery. If the pump is run through the battery switch and circuit breaker panel, there is a high probability that it will be turned off while the boat is unattended. If two pumps are fitted, wire them to two separate batteries.

    Sump Pumps

  • Ensure that all pumps have a high loop in the discharge hose to avoid back siphoning. It is best if the discharge through-hull is well above the normal waterline-while you may get an occasional black streak down the topsides, it is better than flooding the boat through its own bilge pumps.

  • A boat having more than one sump requires multiple electric pumps. With one sump, a small pump might be mounted at the bottom to handle daily drips, while a much larger pump can be mounted higher for a flooding emergency.

  • Non-submersible pumps must have a strainer at the end of the intake hose just like a manual pump.

  • An inexpensive alarm bell wired into the electric circuit will warn you every time the pump runs. The sound should be loud enough to wake you up and be heard over the noise of the engine. Alarm systems separate from the pump wiring can also be purchased to warn of flooding.

Newer-style float switches have no floats. As such, they are more reliable and the dielectric models can differentiate between water and oil, perhaps averting stiff fines and environmental problems.

Engine-driven pumps
One quick way to add bilge-water-removal capacity is to install a Y-valve, suction hose and strainer to the engine's main saltwater intake. The raw water pump on even small diesels can move a surprising amount of water out the exhaust. Here are a few other thoughts:

  • Belt-driven pumps can be belted directly to the auxiliary's drive belt or a separate power take-off. These pumps have a manual clutch to start pumping, but may be fitted with a remotely operated electric clutch. They are available with very high capacities that can double as fire-fighting equipment when their intake hose is T-ed to a water supply.

  • Stand-alone gasoline- and diesel- powered pumps are available for very large craft.

As with all safety gear, test pumps frequently to make sure they are operational. Scrub the bilge and hose it clean, using each pump to empty the water. The boat will smell fresh and you will know that your equipment is ready for your crew to man the pumps.

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