A Guide to the Different Types of Bilge Pump

There are several different types of bilge pump available on the market, each with their own operating features and benefits.

Here is a brief summary of the main types you can choose from.
1. Submersible Electric Bilge Pumps

With reasonable flow rates and low battery drain, DC submersible electric bilge pumps transfer water quietly and efficiently against relatively low heads (vertical heights). This type of pump sits in the bilge and the water is sucked up through the plastic strainer at the bottom of the pump and exits through the discharge hose.
This is a good choice for light, intermittent duties handling relatively clean bilge water.
• Larger submersible models can move water at an impressive rate. Be aware that the flow rate falls rapidly as the discharge head (vertical height) rises.
• Use the recommended hose size – under-sized hose won't harm the pump but you will get significantly less flow.
• Submersible bilge pumps are NOT designed for continuous bilge pumping duties and can burn out if left pumping for prolonged periods.
• These pumps are totally sealed units and it is not possible to service them or replace any of the working parts.
• The submersible electric bilge pump is usually controlled by a simple on-off switch. This can be a dedicated bilge pump switch panel with a built-in fuse, or a toggle or rocker switch built into the boat’s steering console or main switch panel.

2. Automatic Submersible Electric Bilge Pumps with Float Switches

Many submersible electric bilge pumps can have an integral float switch for automatic operation.
As the water level rises, the pump starts. It continues to run until it has reduced the water level to its minimum, and then it switches off.
• These are relatively cheap pumps that offer protection and peace of mind when you are away from the boat in a simple and compact package.
• They usually have three wires so you can connect the pump to a control switch to give ‘off-auto-manual’ activation options.

3. Computer-Controlled Automatic Submersible Electric Bilge Pumps

These pumps operate automatically without the need for a float switch, turning on every 2½ minutes for approximately 1 second.
If the bilge contains water, the pump will sense resistance and will continue to run until no water is present. The computer will then reset itself and the cycle will start again.
• The power used while the pump is in checking mode is minimal.
• These pumps are generally much more compact than those with a built-in float switch.
• They also feature three wires so that you can connect them to a control switch to give off-auto-manual activation options.

4. Remote-mounted Flexible Impeller Pumps (DC)

Remote-mounted flexible impeller pumps self-prime rapidly from dry, can handle moderate amounts of suspended solid matter in the bilge water, and will maintain their flow rate against discharge heads of several metres.
• While they are not as quiet as submersibles, taking more current for less flow at a lower head, they are robust, fully serviceable, and, unlike submersibles, are able to pump the bilge dry almost to the last drop.
• The pump is usually mounted higher up away from the bilge area with a suction hose that can be either fixed in one place or moved around.
• Although flexible impeller pumps can operate for short periods free of water, it is not recommended that they are left dry-running for prolonged periods.

5. Remote-Mounted Diaphragm Pumps (DC)

Remote mounted self-priming diaphragm pumps are compact, quiet and durable.
Self-priming is rapid, the bilge can be pumped virtually dry, and the pump is not harmed by dry-running.
• Discharge heads do not normally exceed 3-4m for any of these pumps.
• They are often supplied with an inlet strainer to keep out solids big enough to interfere with the pump's valves which can’t handle debris like an impeller pump.
• They are robust, and fully serviceable.
• Diaphragm pumps are usually mounted higher up away from the bilge area with a suction hose that can be either fixed in one place or moved around.

6. Engine-driven Pumps
Very few leisure boat owners take advantage of the power of their main engine when it comes to bilge pumping.  Diesel engines need no electrical supply to keep going (ideal in a flood situation) and usually have ample power to propel the boat while driving a substantial bilge pump.
• Engine-driven clutch operated bilge pumps are tough, fully serviceable belt-driven units able to self-prime rapidly and to operate continuously over a wide speed range.
• Installed in innumerable fishing boats and workboats, clutch pumps are becoming very popular in larger leisure vessels, and should be given serious consideration by more leisure boat owners with smaller vessels.

7. Manually-operated Bilge Pumps
A cockpit-mounted manually-operated bilge pump has been a standard installation in most production boats for at least the last 20 years.
These pumps typically feature a plastic housing with a large neoprene rubber diaphragm with inlet and outlet valves.
• A pump handle can either be fix-mounted to the diaphragm clamping plates, or a removable handle can be slotted into a socket in the actuator fork assembly.
• Manually-operated bilge pumps can either be directly bulkhead mounted, or more often under-deck or behind bulkhead mounted to keep them out of the way. With this second type of installation a deck plate lid conceals the socket into which the bilge pump handle is inserted.
• Fully serviceable with spare parts readily available, smaller manual bilge pumps offer reasonable flow rates suitable for clearing bilges of accumulated rainwater, waves or deck wash.
• The larger capacity manual bilge pumps can give better flow rates, however should still not be relied upon as a primary bilge pump for clearing larger flood waters.

8. Bilge Strainers
Most bilges collect more than just water. Small solid objects and assorted debris find their way into the bilge too. 
Floating material will tend to accumulate around the inlet to the bilge pump or bilge pump suction hose. A strainer will keep out anything large enough to damage or stop the pump.
There are two good reasons to fit a strainer to the inlet hose of your bilge pump:
1. The cleaner the water that enters the bilge pump, the more efficiently the pump will work, the less attention it will need and the longer it will last.
2. Floating and suspended solid matter is drawn towards the inlet pipe when the pump is working.  A strainer increases the inlet area and helps prevent choking.
Whether your pump is manual, electric or engine-driven, fit a strainer of ample size, inspect it regularly and clean it when necessary.
To see the range bilge pumps available for leisure and commercial vessels, click here or for further technical advice, contact the Safety Marine technical team on advice@safety-marine.co.uk or call +44 (0)2380 226300.


The Beacon Logo

For the latest marine safety news each month, regulation changes and invaluable practical safety advice, simply submit your email address.