A mechanically simple device, a Bilge Pump Float Switch triggers a bilge pump as the water level in the bilge rises. One part of the switch is buoyant. This part called the 'flapper' will rise with the water and turn on the pump. Float switches are manufactured by almost every major pump manufacturer and have been used in bilge pump systems for decades.

Float switches have a high rate of failure. They stop working for a number of reasons but the design of the switch is typically sound. More often than not, failure of a switch is the result of lack of maintenance or poor installation. Every type of boat, sailboat or powerboat, requires regular maintenance to avoid costly repairs. Electric submersible bilge pumps are no exception. They are not self-cleaning and must be regularly serviced in order to operate properly.

Covered vs Open

The two types of float switches are open and covered. Closed switches are typically enclosed in a plastic casing. The covering protects the 'flapper' and allows it to raise unhindered. Problems like water surge, loose hoses, or other debris, do not typically affect a covered float switch. Unfortunately, it is difficult to test a covered switch to see if it has become clogged with bilge slime. Open switches can suffer from water surge if improperly installed and can be covered with loose items preventing their proper operation. However, they are easy to test and clean. We recommend open float switches.

Installing and Maintaining a Bilge Pump Float Switch

There are 4 main steps to installing and maintaining a hassle free float switch:

1) Bilge is debris free - ensure that your bilge is free of debris and clean. A slime or sludge can be created over time from a mixture of oil, bilge water, and random sea debris. This slime wears down your bilge system components and can prevent them from functioning. There are many products on the market designed to clean a bilge. One of the most simple solutions is using Dawn dish soap, a stiff scrub brush, water (bucket or hose), and a wet/dry vacuum. The downside to this solution is that plenty of elbow grease is required.

2) Switch flapper is able to rise and fall freely - loose items in the bilge like hose or wiring will prevent an open float switch from operating properly. Use zip ties and mounts to secure loose wiring and hoses. Another alternative is to use a covered switch.

3) Proper wiring is essential - improper wiring can destroy your bilge pump system. Be sure to carefully read your wiring diagrams that come with your float switches or pumps. If you do not have access to the correct wiring information, you can pick up a copy of Boatowner's Illustrated Electrical Handbook. This handbook will teach you how to correctly wire your boat's electrical system. There are also forums and other free diagrams out there on the internet.

4) Bilge surge must not affect the switch (open switches) - If the switch is placed directly in the path of water flooding into the bilge, that switch is affected by 'bilge surge.' This surge will improperly trigger the bilge pump(s) which can damage your pump system (pumps don't like to be run dry). This problem can be avoided with correct installation. The switch should be placed within three inches of a bulkhead with the flapper facing aft. If it is oriented to the bow, the switch will almost certainly be damaged.

What is the best brand?

So who makes the best float switch? Consumers tend to be brand loyalists and wont switch brands unless they have a negative experience with a product. When choosing a float switch, look for features like easy-clean removable bases and quality marine block wiring. Warranties are also important so make sure you read them carefully to see what is covered in the event of failure or damage. There are many quality switches on the market but you get what you pay for. In the long run, it will be worth it to spend a little more money.