Bilge pumps serve two primary functions: maintaining a dry bilge by pumping gray water (if there’s no separate gray water tank), water from packing glands, small leaks, and other over-flow fluids; and in case of emergency, controls flooding from a major leak until the leak can be stopped.
TYPES
There are two main types of bilge pumps in common use, electric and manual. A third option is the engine driven pump.
Electric bilge pumps are generally thought of as maintenance pumps, but with several high GPH capacity pumps in the bilge, they can also be used for emergencies. Most electric pumps can be wired so that operation is completely manual, or with the addition of a float or water-level switch and three-way control (off-manual-automatic) can be made to turn on automatically.
constitute the majority of electric
pumps in use.
- They’re designed to be located in the lowest part of the bilge and pump water as it rises around them. The motor/ pump assembly is submersible.
- They’re rated for continuous or intermittent duty and are generally not self-priming.
- Centrifugal pumps can operate dry for short periods of time.
Diaphragm pumps offer an option to centrifugal
pumps.
- Diaphragm bilge pumps literally suck the bilge dry like a wet-vac using an intake hose to the low point of the bilge, unlike the centrifugal pumps that leave a low level of water in the bilge.
- These pumps are self-priming but because of their numerous parts, like check valves and diaphragms, require more maintenance than centrifugal pumps.
- They are not submersible.
Manual bilge pumps are generally considered emergency bilge pumps, because of the large amounts of water that can be moved through them. Also, if the electrical system goes down, there’s an alternative to the electric pumps. Manual bilge pumps can be either lever and diaphragm style, or piston style pumps.
- Diaphragm bilge pumps
are self-priming, single or double action diaphragm type pumps, with a single or double diaphragm, a lever, and valves. - Diaphragm pumps can be fixed or portable.
- The larger pumps can move up to 50 gallons per minute.
- Depending on the material used for the diaphragm and valves, oil and other wastes, as well as water, can be discharged through these pumps.
- Piston bilge pumps
are self-priming, single action pumps. - Piston bilge pumps can extract most fluids, even fluids with abrasives (salt water).
- These pumps are extremely portable. They can be used to pump out a boat tender, as well as the bilge of the mother ship.
- The ones constructed from lightweight plastic material won’t mar the boats surfaces if dropped.
- They remove about one gallon of fluids per four strokes.
Engine drive bilge pumps are self-priming, high-volume, belt-driven impeller pumps.
- These pumps run off the engine’s crankshaft pulley and are set into operation by either a manual or electric clutch.
- Do not run these pumps dry.
- Engine driven pumps, depending on the hose size and engine RPM at which the pump is driven, can move up to 3,600 GPH.
- Because of the large volumes of water, these pumps can fight fires or be used for deck wash down if the intake is teed into a water source.
ACCESSORIES
- A high-water bilge alarm wired to the float switch will alert you to unusually high water in the bilge.
- A signal lamp or audible alarm at the helm provides an alert that the bilge pump is running.
- An above-deck remote control to turn the pump on or off.
- A counter for every time the pump runs, or the length of times it runs, can advise of a continual leak or potential problem.
- Strum boxes, or strainers, keep debris out of pump intakes, avoiding clogging and pump damage.
TIPS
- Latest technology includes microchips, magnetic floats, and sensors to determine the difference between petroleum and other fluids prior to discharging, thus avoiding inadvertent discharge of illegal pollutants.
- Centrifugal pump ratings are based on unrestricted discharge flow and the pump motor operating at continuous full voltage. The voltage at the pump motor, head (the discharge height the pump works against), length of hose runs, hose bends, and even the hose interior surface affect bilge pump performance.
- Screens on the intake hose end reduce clogging, but the screens need to be cleaned periodically as part of a maintenance schedule. Centrifugal pumps are usually mounted inside a slotted enclosure to minimize the intake of foreign objects.
- To prevent back siphoning, install a vented loop on the discharge side instead of check valves. The pumps don’t create enough force to overcome the resistance of the check valve. Remember to take the loop into account when determining the GPH size pump required.
INSTALLATION
The average-skilled sailor with basic tools and some electrical skills can install a bilge pump.
Toolbox
Electric bilge pumps require:
- Tin-plated wire,
- Connectors
- Wire cutter/stripper/crimper
- Wire ties or clips
- Multi-meter
- Soldering iron if required
- Additional circuit breaker for electrical system if required
- Hose rated for the use and stainless steel hose clamps
Manual bilge pumps require:
- Drills and bits
- Bolts, nuts, and washers
- Screwdriver
- Hose rated for the use and stainless steel hose clamps
Engine driven bilge pumps require:
- Tin plated wire
- Connectors
- Wire cutter/strippers for electric clutches
- Wire ties or clips
- Hose rated for the use and stainless steel hose clamps
- Drive belt, engine bracket, and spare drive shaft pulley or PTO
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