The Blue View - Bilge Pumps

bilge pump Nine of Cups has four bilge pumps in place – one electric pump with a 3700 GPH (gallon per hour) capacity, one electric with a 500 GPH capacity and two hand operated 3600 GPH pumps. And if all else fails, we have several buckets aboard. Discounting the buckets, if both electric pumps were running and Marcie and I were giving it our all at the pumps, we should, in theory, be able to pump more than 11,000 GPH, or almost 200 gallons per minute! That should handle just about anything, right?

If you've followed our blogs over the years, you may remember a few that talked about bailing water from Nine of Cups. I can recall three occasions when we were at sea and taking on water – a most distressing situation. The leaks turned out to be relatively small and easily repaired, but what was more distressing was that the combined output from three of the four bilge pumps would barely keep up with even those small leaks (Marcie was hand pumping while I tracked down the source of the leak). Had we suffered some serious hull damage, all four of the pumps would not have even come close to handling the water ingress. The best we could have hoped for was that our pumps would buy us enough time to fix the problem, get help, run Cups aground on a beach somewhere – or, sigh, get the life raft deployed and loaded.

On the other hand, our bilge pumps are adequate for routine water ingress, minor emergencies and pumping out all the collected water once the emergency has been handled. Here are my thoughts on a reasonable bilge pump system.

bilge pumps

  • Small Automatic Pump. We have a small pump (500 GPH) with an automatic switch located in the lowest part of the bilge. This pump takes care of routine water ingress. We almost always take on some water during rainstorms or from waves over the bow or into the cockpit during rough weather. A small capacity pump is desirable for this application. When a bilge pump runs, it has to pump water out of the bottom of the bilge to a height above the waterline of the boat. When the pump shuts off, all the water in the hose will eventually run back down through the pump and back into the bilge; the bigger the pump, the bigger the hose, and the more water that will make its way back into the bilge. Thus, a smaller pump with 3/4” diameter hose is preferable. It is controlled via a switch on the breaker panel and an automatic switch – see below for a discussion on automated switches.
  • Large Capacity Electric Pump. We have a large capacity (3700 GPH) electric pump located next to the small pump. It is not automatic, and is turned on via a switch on our breaker panel. This pump is used in emergencies or when more than the usual amount of water has made its way into the bilge. For example, when it's time to clean the bilge, we first use oil absorbent pads to collect any fuel or oil, then turn off both pumps and pour several gallons of fresh water mixed with an acceptable bilge cleaner into the bilge and let it set a day or so, allowing it to slosh around. Next we turn on both pumps, quickly pumping the cleaner out and cleaning the hoses at the same time.
  • Hand Operated Pump #1. This hand operated pump is permanently mounted below the cabin sole and while primarily intended for emergencies, is used more frequently than you might think. On passages, we usually turn off the automatic pump and use the hand operated pump once or twice a day to determine whether we are taking on more than the usual amount of water. By counting and tracking the number of pumps required each morning to empty the bilge, the early signs of a pending problem, like a leaking fitting, can be identified before it becomes an emergency.
  • Hand Operated Pump #2. This pump is attached to the underside of one of the cabin sole hatches, along with 15' (4.5m) of hose. In an emergency, the hose can be fed down into the bilge and the pump taken up into to cockpit and operated there.
  • Automatic Switch. I have tried a multitude of automatic bilge switches, most of which didn't work reliably. The mechanical float switches would sometimes stick, or would run the pump dry while on a heel. The automatic bilge pumps have a tendency to cycle on and off frequently as the water is pumped out of the bilge, then drains back down into the bilge from the hose. (See the further discussion below regarding non-return check valves in the discharge hose).I do like a few of the electronic sensors that detect water level by measuring the capacitance between two sensor pads. The capacitance will be different depending on whether there is air, water or fuel between the sensors, and since it can detect the difference between oil/fuel and water, the switch has been programmed to turn the pump on only when water is present. Since oil and fuel float on water, the switch will then turn the pump on only until all or most of the water is pumped out, and turn the pump off before any oil or fuel gets pumped overboard. The switch I use is the Water Witch Model 101*. One of its features is that it keeps the pump switched on for several seconds after the level of the water drops below the sensor. If the switch is mounted above the bilge pump, the pump will continue running until the water level drops well below the sensor height, so when the water left in the hose drains back into the bilge, the water level will still be well below the sensor, preventing it from cycling on and off.

water witch

  • Check Valves. A non-return check valve will prevent the water in the hose from draining back into the bilge. The ABYC allows the use of a check valve in the discharge hose of an automated bilge pump for just this purpose - to prevent the pump from cycling on and off. I'm not a big fan of check valves in bilge discharge lines. Since the bilge water often has debris in it, the check valve often becomes fouled, causing it to leak and rendering it useless.
  • Operational Feedback. Having some sort of feedback to let me know the automatic bilge pump is running is important. We have an indicator light on the alarm panel that illuminates when the pump is running. On my wish list is the addition of a cycle counter – a device that keeps track of how many times and for how long the bilge pump has turned on. An increase in the amount of time the automatic bilge pump has come on may well be an indicator of a problem that is simple to fix now, but which could be catastrophic if allowed to get worse.

alarm panel

  • High Water Alarm. We have a water activated switch located well above the normal level of water in the bilge. If the water ever rises to the level of the switch, it sets off audible and visual alarms both below deck and in the cockpit. I use a different model Water Witch switch for this application – the Model 10, which is identical to the Model 101 but without the shut-off delay. We installed it after our passage from Easter Island to Ecuador when we began taking on water and were blissfully unaware of the problem until the floorboards were almost awash with water.

So that, in a nutshell, is our bilge pump system.

BTW, I want to thank our JALF blog reader, Tony in California, for suggesting this blog. I thought I had covered the topic long ago, but neither Tony nor I could find an older Blue View on the subject. So, thanks Tony.

This is a link to the Water Witch bilge switch on Amazon. If you buy anything from Amazon using this link, it costs you no more, but we make a tiny percentage on your purchases.