Bilge Pump Switch for all your boating needs. Check out the technical explanation on this fun subject from our Marine Engineer. Brand new designed, fail-safe switch with no moving parts NOW available in prototype!

Bilge Pump Switch H2O Marine
Don't sink your boat due to a float switch!

DON’T sink your boat!

Our Marine Engineer: Bazza Cooper Bazza has spent his entire life around boats. Anything from small fishing boats to large commercial and domestic craft. For a couple of decades, his only addresses were floating ones! In that time, he has lost count of the number of small and up to multi-million dollar “In- survey” craft sink due to a failed bilge pump or bilge pump switch. I cannot think of any other life-saving piece of equipment that is so routinely poorly installed and maintained to the point where they are life-threatening!

Bazza Cooper Marine Engineer. H2O Marine Products and Services
Bazza Cooper

Why is Bilge Pump Systems poorly maintained?

Bilge Pump Systems fall into the same category as items like liferafts. They cost money; they sit there doing nothing most of the time. Then you need to do some maintenance on them occasionally. Other than that, we tend to forget about them. UNTIL…. You are at sea, and your boat springs a leak. Then you hope and pray that your pumps work to every bit of their 100% rated capacity. Kind of like your liferaft if your boat starts sinking. By the nature of what they are and what they do, they tend to fall into neglect. We are all guilty of it. I don’t know how many times I have thought to myself, “I don’t think I have checked the bilge system operation in awhile.” And you know what, I STILL did not find time to get it done! They are always in the lowest, dirtiest, and most awkward place to get at. So, if possible, we tend to avoid that work. I once worked on a multi-million dollar yacht. Our yacht had electric bilge pumps plus a complicated manifold system. That allowed the use of four separate pumps as bilge pumps. When I first joined the boat, I checked out all the bilge pump systems. Not one was working. This is typical! Visit the grotty pictures of replacing a bilge pump float switch “old style” You would be used to seeing Float Switches look like this:

Float Switch
Float Switch

How did Bazza develop our Bilge Pump Switch?

As a Marine Engineer and Inventor, my vessels have always had “Bazza’s little extras” located deep in the depths of the bilge. A way of “for certain” knowing what was going on. Or, more importantly, not going on without having to look. And before it becomes a problem. Excellent for our vessels, but they have always been one-off designs that work perfectly, but way too complicated for most situations. For many years, I have thought that I should put together a bilge pump system that is modular, simple to install, and understand. But, most importantly, it should be as fail-safe as possible. By fail-safe, I mean that if ANYTHING fails, it should fail in a way that is least likely to do any harm. In a vessel bilge system:

  1. Any failure should alert the operator before it turns into a major, and perhaps, life-threatening problem.
  2. It must also contain a second independent sensor to monitor for high-level water alarm.
  3. No matter what, there can always be a situation where the bilge pump is indeed working, but not keeping up with the inflow. Not keeping up with the inflow could be because of pump blockages or just too much water ingress into the boat!

You should know not only if your pump is working but also how well it is working.

H2O Marine Workshop
Baz Cooper Workshop

History of Bilge Pump Systems and Switches

For many, many years in the past, bilge pump switches contained mercury, a metal that is liquid at room temperature. A simple hinged float with a small amount of mercury located within would float up when immersed in liquid. Floats would cause the mercury the pool within the float where a pair of electrical terminals are. The liquid metal would short the two terminals together, creating a closed switch. These worked great as switches, and the electrical connection between the terminals was always perfect, and they could switch large currents effortlessly and at any voltage. The electrical side of the switch was very reliable. Of course, they still suffered from sticking when dirty and sometimes would leak, fill with water, and sink. Mercury, as we all know, however, obtained a bad reputation and has been removed from many applications.

Bilge Water Pump Problems

Any experienced boat owner or Captain will be familiar with the last bilge water that the pump is unable to remove. When you are sailing, it is sloshing around and triggers the bilge pump each time you hit a wave. Sailing makes the water slosh to the float switch momentarily, turning on the pump. Only to be turned off moments later when the water sloshes away from the switch. Sloshing water against bilge pump switches creates several problems.

  • If you are relying on a ball bearing to keep you afloat, it will add another burn mark every time the pump switches on and then another when it turns back off.
  • Bilge pumps use electric motors. Motors use much more current during start-up than during use. More current is an inductance thing and means that during start, they create much more heat than when running. By always short cycling, it causes pumps to overheat.
  • Bilge pumps have a seal that keeps the bilge water from entering the pump motor. Let’s talk about how this can be a problem in your bilge pump system.

Good quality pumps that pass ABYC standards must pass seven hours of dry running without any seal damage. Seven hours is not very long if you have a pump that is continuously short-cycling. Only one night with a float switch stuck will meet seven hours. This seal lubricates by the presence of the bilge water. If a bilge pump continues to constantly short-cycle from dry without having sufficient water lubrication the pump shaft seal, then it will tend to burn the shaft seal out. More extended can happen reasonably rapidly and allows water to enter the pump ending in internal damage in the open-circuited pump.

Progression of Bilge Pump Switches

The answer to the mercury problem was to replace it with round steel ball bearings. The balls roll back and forth, making or breaking the electrical connection just like mercury! Perfect! Well, no, not exactly. Although most float switches now operate like so, unfortunately, pump motors are what is called an inductive load. These inductive loads have a nasty habit of creating a significant power demand as they start and another huge voltage spike within themselves as they DE-energize. This power surge when the system begins causes an arc at the electrical connection point. We have all seen a wire spark as it is connected. Even worse, is the disconnection point. The massive voltage spike as the contact opens creates a small arc on the ball as it starts to roll away from the connection. And, the larger the pump is, the larger and more prolonged the arc is. Eventually, the ball may roll down to the contacts one time when the float rises, and one of the tiny little burns on the ball “may” line up with the connection. Then the switch will fail to turn on. Burns, of course, never happened with the mercury acting as the switching mechanism! That is why we ( the more mature folks among us) remember the old float switches as being not only the only real choice, but they were, for the most part, reliable. Not so much anymore. Without any backup systems, this can easily lead to a sunk boat 🙁

Bilge Pump Switches H2O Marine
Don't let your boat get like this due to a broken bilge pump switch

Non-Moving Electronic Switches

Non-moving electronic switches have been around for some time. Some are good, some are bad. Getting rid of the moving part is always going to be far more reliable than relying on a small float with little buoyancy always to be able to float up when constrained by its hinge. Many vessels have met their demise because the end of an old zip-tie jammed the float or a bilge sock moving over a float switch. The first of the electronic-based switches used metallic probes. These metallic probes require a minimum current to flow from one probe to the other through the sensed liquid. These switches have proved reliable; just ask the US Coast Guard. They all use this type of electronic switches on their boats. One disadvantage of having these probes down in the salty bilge is that one of them must, by design, be at a higher potential than ALL of your grounded and wire items sitting in your salty bilge. Therefore this may present an issue with stray currents and electrolysis.

Capacitive Sensing Bilge Pump Switches

Technology moves on, and now the top bilge pump manufacturers are using capacitive sensing in their automatic pumps. Capacitive sensing is the same technology that your smartphone uses to know that your finger is on its screen. It is a well-developed technology and what we use as it is the smartest choice. It always works, there are no moving parts and no stray current to worry you.

H2O Bilge Pump Switches- Moving Forward

I have considered all the above points, creating a switch that solves the pain points. Not only to function correctly as a liquid level switch, but also to monitor the pump, the switch, and associated vessels wiring and alert the operator of faults before they become an issue. Features – H2O Bilge Pump Switches

  • Solid-State with no contacts to fail.
  • No moving parts, nothing to jam from debris in the bilge.
  • No loose parts to stick or sink.
  • A three-second turn-on delay to prevent false triggering from any sloshing of water.
  • An Eight-second turn-off delay to clear the pump piping, which prevents short-cycling.
  • Massively oversized switching components.
  • Super Small, lightweight, low profile sensors that can be mounted almost anywhere to remove that last drop.
  • 18-inch sensor leads from switch to the sensors to keep all connections well high and dry.
  • All electronics potted for waterproof integrity.
  • Sturdy ABS drip-proof box with a clear lid for waterproof connections.
  • Indicator LED’s to indicate: 1) Power to Switch 2) Pump Active 3) Alarm active.
  • The LED’s are mounted under a clear box cover for protection.
  • Screw terminal connections to form simple, strong, electrically stable connections.
Bilge Pump Switch H2O Marine
Bilge Pump Switch H2O Marine

Failure Point of Electronic Switches

The number one failure point of electronic switches is the switching transistor. We use two transistors for redundancy, each one capable of switching ninety amps. Our switches test to twenty amps in a sixty degree Celcius environment. We also use two snubber diodes to remove the spikes caused by inductance. We rate them at seventeen amps and set the alarm thresholds to trigger at a current draw below one amp and above 17.5 amps. Our switches have a high safety margin built-in.

Bilge Pump Manual Switch at the Helm

Our Bilge Pump System Switch monitors the manual switch at the helm. When it detects that the pump activates from the manual bypass switch at the helm, then the switch turns itself on for eight seconds. It will direct full power to the pump reducing the voltage drop associated with the longer wiring between the helm and the pump. Most governing bodies specify a 2% or 3% maximum voltage drop allowed in bilge circuits. But, many vessels fall way short of this. Typically closer to 10% and sometimes even more. Even at a 3% drop, the pump will have 3% more power and pump more water with the switch activated. After 8 seconds, it will recheck the helm switch.

H2O Marine Workshop, Victoria BC
One of our H2O Marine Workshops in Victoria BC

Additional Features of our Bilge Pump Switch

H2O Bilge Pump System Switch also monitors the pump’s current draw. It will detect if the pump is operating within the tolerance levels, and it will trigger an alarm if not. An alarm situation does NOT affect the operation of the bilge pump switch, but it alerts the operator to a fault. Our system will immediately alert you to a corroded through the bilge pump wire connection, which is the #1 reason that boats sink. A burnt out or short-circuited bilge pump will trigger an alarm, along with many other faults. Our H2O Bilge Pump System Switch has a high water bilge alarm that uses a separate sensor that does not require the bilge switch circuit to be operational to trigger. The alarm system is  FAILSAFE! Under normal conditions, the alarm output has 12 volts present. The twelve amps hold the alarm relay closed at the helm. During a high-water alarm or an alarm caused by the switch’s current detection function, then: if the alarm terminal loses its 12-volt signal, unlatching the relay at the helm will cause an alarm to sound. This alarm will also occur if the power to the bilge switch is lost. Or, wiring between the bilge switch and the helm alarm breaks. Our alarm alerts the operator before a critical situation arises.   Check out our Marine Services and Products Page for more information and links to purchase.

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Bilge Pump Switch H2O Marine
Our small, compact, H2O Bilge Pump Switch

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