Bilge Pumps


All boats are required to have a means of bailing water out of the boat. In a row boat or kayak a simple bailing scoop or a portable manual pump might suffice. As the vessel size increases a bailing scoop becomes impracticable so it is common to see larger manual built in pumps or if power is available an electric bilge pump. Electric bilge pumps are available for different voltages in AC or DC current. The popular electric bilge pumps are the impeller submersible type. This means they do not use valves unless an inline check valve is installed and are constantly sitting in a pool of water. Rule Industries®, Attwood® and Johnson Pump® all produce bilge pumps for a variety of bilge designs. Over time this can cause a bilge pump to malfunction therefore periodic inspection is strongly advised. There are also engine driven bilge pumps that attach to the engine such as the ‘Jabsco®’, self-prime magnetic clutch impeller pump.


Types of Boat Bilge Pumps


Not all marine bilge pumps are the same. Aside from size and capacity, there are also different types. The four most common types are:
  • Centrifugal Bilge Pumps move water by turning rotational energy into kinetic energy. Inside the pump, a spinning impeller pushes water into the discharge. This creates low pressure in the pump, which sucks more water in.

  • Diaphragm or Reciprocating Bilge Pumps work by using a diaphragm or piston and check valves. The diaphragm or piston pulls up, creating a vacuum in the pump that sucks water (or air) through the inlet check valve. When the diaphragm is pressed down, this forces the water out through the outlet check valve.

  • Flexible impeller Bilge pumps use a rubber impeller and a cam to function. As the spinning impeller meets the cam, it bends, squeezing its trapped water out the discharge. When the impeller leaves the cam, negative pressure creates a suction that pulls in more water.

  • Manual Bilge Pumps are vital for most recreational boats. If water gets to your electrical components, your bilge pump will shut off. The only way to save your boat or buy time then is by using a manual bilge pump.


Bilge Pump Size and Number of Bilge Pumps Requried by Law


Passengers:Vessel Length:Bilge Pumps Required:Minimum Capacity Required:
Less than 4926-65 ft. (7.9-19.8 m)1 power pump & 1 portable hand pump or…10 GPM
… 1 fixed hand pump and…10 GPM
…1 portable hand pump5 GPM
< 26 ft. (7.9 m)1 portable hand pump5 GPM
Over 49 + Ferry Vessels< 65 ft (19.8 m)1 power pump and…25 GPM
…1 portable hand pump10 GPM
Any Number> 65 ft (19.8 m)2 power pumps or more (depending on design)50 GPM


Bilge Pump Panels


With electric bilge pumps there is the option of an automated system that will turn on the boat bilge pump automatically. Automated boat bilge pumps are commonly installed with an bilge pump panel such as the 3-Way Illuminated Rocker Panel Bilge Pump Switch manufactured by ‘Rule Industries®’ or the Contura Water Resistant Bilge Pump Control Panel, manufactured by ‘Blue Sea Systems®’. These type of switch panels offer the option of either a manual mode of operation where the operator will turn the electric bilge pump on or off, or the automatic mode where the pump is activated by a sensor. There are a number of sensors for automatic bilge pumps for boats such as float switches, electronic sensors, pressure sensors to name a few. Alarms are also available as an option with some providing an audible sound when the sensor is activated or merely a light.



Bilge Pump Sensors


Float Switches such as the ‘Rule-A-Matic®’ line of bilge pump float switches from ‘Rule Industries®’ or the other manufacturers such as ‘SeaChoice®’, ‘Attwood®’ and ‘Johnson Pump®’ are the most common sensors for automatic boat bilge pumps. Electronic units are gaining popularity. One of the challenges of switching a bilge pump is the sudden rush of current and in a DC system it is not long before the contacts are arced away requiring a replacement sensor. Therefor is important to periodically test any bilge sensor for performance.


Bilge Pump Parts


There are parts available for most bilge pumps, be it a new motor, a new strainer or an impeller. Even manual bilge pumps are well serviced with replacement parts such as new bellows, valves and bracketry. There is tremendous innovation with bilge pumps and new products continually coming into the market and fortunately there is still a fair amount of support for legacy products with spare parts readily available.


Bilge Pump Plumbing


A bilge pump system would not be worth much if it was not for the plumbing. A foot valve, a length of bilge hose, stainless steel hose clamps, an inline check valve and a through hull fitting all make up on portion of the bilge pumping system. Although these items require less maintenance, they are not immune to failure and should be part of the bilge pump inspection.