Bilge Pump Float Switch

*IMPORTANT* – Make sure you match the float switch exactly to your boat’s electrical system. This will prevent premature pump burnout, shorts, and other electrical errors.

Relatively cheap, a Bilge Pump Float Switch is a simple device that activates the bilge pump as the water in the bilge rises. The ‘flapper’ of the switch is buoyant and will trigger the bilge pump as it floats with the rising water level. Nearly every major bilge pump manufacturer produces some type of float switch. Float switches have been used for decades to control bilge pumps.

With a high rate of failure, float switches can easily become a major headache. They can fail for many reasons but poor design is typically not the culprit. Failure is typically the result of poor installation and a lack of maintenance. Boats require a significant amount of maintenance in order to avoid problems that can cost hundreds of dollars or leave you stranded in the middle of nowhere in dire straits. The engine/sails and hull are not the only components of a boat that needs regular maintenance. The bilge, the bilge pumps, and the float switches that activate them must be regularly cleaned in order to function properly. Float switches are not self-cleaning and must be maintained in order to preserve the life of your bilge system.

Open vs Covered Switches

There are two basic types of float switches: open and covered. A float switch that is enclosed is protected from problems like loose wiring and hoses that prevent the flapper from pivoting properly. Covered switches also prevent problems related to water surge. However, you can’t easily test the covered switch to see if it’s working. Even though it’s covered it will still become clogged with bilge slime. Both types of switches will require cleaning. Open float switches are recommended. They are easier to clean and test. Avoid problems with bilge surge by following the principles below.

Installing and Maintaining a Float Switch

There are four main steps to installing and maintaining a reliable float switch:

1) No debris in the bilge – make sure that your bilge is clean and debris free. This sounds like an easy proposition but oil in the bilge water can make a sludge over time and that sludge can accumulate dirt and other debris. There are dozens of cleaning products on the market that can help keep your bilge clean. One of the easiest solutions is Dawn dish washing soap, a scrub brush, water, a wet/dry shop vac, and plenty of elbow grease.

2) There should be nothing that interferes with the rise and fall of the switch. Depending on how the switch is designed, a loose wire or hose can prevent the switch from working properly. Secure your hoses and wiring using zip ties and mounts. If anything ends up on top of the flapper, the pump is unable to operate and the bilge will not be pumped dry.

3) The float switch must be wired properly. Wiring is crucial as it can affect the longevity of your bilge pumps. A float switch that is not properly wired can run the pump when not needed or prevent the pump from running when the bilge is filling with water. Be sure to carefully read the float switch instructions. If your instructions are incomprehensible or just plain lost, you can pick up a copy of the Mcgraw Hill Boatowner’s Mechanical And Electrical Manual; Third Edition. This excellent guide will visually teach you how to properly wire a boat’s electrical system including the float switch. There are also many free diagrams and forums out there on the internet.

4) The switch must be protected from the flood of water entering the bilge. The float switch should not be placed directly in the path of water entering the bilge as it will trigger the pump(s) unnecessarily. The orientation of the flapper on the float switch is crucial here. Place the switch within 3 inches of a bulkhead with the flapper facing aft. If the flapper is oriented towards the bow of the vessel, the rushing water can and will severely damage the float switch.

Which Brand is the Best?

There is a strong debate over the topic of what brand makes the best float switch. Rule produces many fine float switches with warrantees ranging from 2-5 years. Most people are brand loyalists and use the brand they have experience with. They have no reason to change brands unless they have a negative consumer experience. Float switches fail at a notoriously high rate unless properly installed and maintained. That being said, there are some features like removable bases for easy cleaning and quality wiring that can make all the difference. Every brand has both positive and negative reviews. Typically, the negative voices are louder and more forceful than the positive. There are plenty of quality switches out there and you will typically get what you paid for. Spending a little more money is worth it in the long run. Buy a quality switch with excellent reviews that fits your needs and you can avoid the stress of float switch failure.