Choosing a Bilge Pump

What are Bilge Pumps?

Bilge pumps are devices used in boats to remove unwanted water from the bilge compartment of a boat. (The bilge is the lowest compartment of the inside hull of a ship.) Whether you have a sailboat or powerboat, they are as important as lifejackets in an emergency. If there happened to be a collision that caused a leak, having a bilge pump actively removing water from the boat’s compartments could buy you precious time. However, as many experience boaters know, you cannot rely on a pump to keep your boat afloat indefinitely.

Main Types of Bilge Pumps

Non Automatic:

Non Automatic pumps are controlled by means of a float switch and/or a manual panel switch. The panel switch allows you to control the pump remotely. Using the float switch is beneficial because the pump only runs when the water reaches a certain level. After the water is pumped out and the level goes back down, the pump can shut off. The most common type of non-automatic pump is the Electrical Submersible Bilge Pump. They are easy to install, very effective, and have low amp draw. Also, the motor cartridge can be easily removed to clean out debris and other obstructions.

Automatic:

Automatic Bilge Pumps function without the use of a float switch. It uses the principle of impeller resistance to sense if any water is present. Depending on the brand, the pump will automatically turn on every 2.5 minutes to check for water. If water is present, the pump will know about it from the slight pressure on the impeller as it spins. It will continue to run until all the water has been pumped out. The voltage needed for both automatic and non-automatic pumps will vary from 12V – 32V, depending on the size and capacity of each pump.

Manual:

If the boat’s electrical system goes out, a manual bilge pump would be invaluable. They are able to move lots of water effectively, but can be tiring to use. Water is heavy, and that weight is compounded when moving it some distance. When installing these sorts of pumps, take into consideration the ease of access, and imagine how it will be used. Putting a manual pump in a tight, cramped space may hinder your use of it when it is needed.

Which Pump is best for your boat?

The first thing to consider is the size of your boat. Smaller boats will need a good size pump because the bilge compartment is smaller and will fill up with water quicker than larger boats. Some boats have separate bilge compartments. If that is the case, it would be a good idea to have a pump for each section.

Most electric pumps are rated for the number of gallons that they can pump in an hour. (G.P.H.) It is recommended to select a pump the largest model that is still practical for your boat.  Also consider the size of your existing output hose and the capacity of your boat’s wiring and battery. Don’t hesitate to ask an expert when making these decisions. You can talk to a pump manufacturer and get their informed opinion.

Suggested Pump Capacity:

Boat Size

Number of Pumps

Pump Output in GPH

16’ – 20’

2

2500

21’ – 26’

2

3000 – 3500

27’ – 35’

3

3500 – 4500

36’ – 42’

3

6000

43’ – 49’

3

8000

50’ – 59’

4

9000 – 10,000

Where to place Your Bilge Pump(s)?

It is always a good idea to have more than one bilge pump onboard. Many boaters have a backup pump installed in the same bilge compartment. The first pump may be smaller and positioned where the majority of water will pool inside. The secondary pump may be a bit higher inside the hull. This pump should be bigger than the first, because if the boat has collected that much water the main goal is to get it out as fast as possible.

When deciding where to place your pumps, observe where the water accumulates in the hull when the boat is at rest as well as in motion. For powerboats the water tends to flow toward the aft when the boat is moving. Sailboats tend to accumulate bilge water in the middle.

Bilge Pump Installation Reminders:

  • Follow the manufacturer’s specifications – especially on wires sizes
  • Use a vented loop – if the thru-hull discharge can be submerged, a siphoning effect can fill your hull instead of empty it.
  • Keep discharge hoses short – long hoses make the pump work harder than it has to.
  • Use waterproof connectors – any connections in the bilge area should be protected.
  • Use smooth bore hoses – corrugated hoses are cheaper but not effective for pumps.

Bilge Pumps Available from the Bottom Paint Store

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