Bilge pump basics for the novice to the expert

Bilge pumps, we all have them or should have them; they have saved many a vessel and it would be crazy to go to sea without one.

The thing about a bilge pump is that you do not give them much thought until you need them, it can be something as simple as clearing the bilges automatically every ten minutes because the stern gland has started to leak with a hundred miles left to run before landfall. While it would be possible to do this with a bucket however, the truth of the matter is the electric or fitted manual pump is convenient and just so much easier to use.

On that same note the electric pump can take control and clear the bilges without you needing to get a look in. But with this automation you need to be sure it has been done right and have some form of back up or alarm if things do not go as they should.

Not long after taking possession of our boat we almost sunk while tied alongside due to a series of events and the bilge pump system was right there in the middle of it. I would even go as far as saying it was the cause of it.

With the usual excitement of having a new boat, while not entirely new, it was new to us. I was cleaning under the floors and in the bilges with a garden hose.

This was not an easy job and required plenty of elbow grease because, like a lot of boats, the bilges and under the floorboard spaces had not seen the light of day or a clean for some time.

While I was washing and scrubbing, I collected and removed an assortment of debris but furballs were top of the list, followed closely by small amounts of sawdust and the odd cable tie off cut. During the job I kept an eye on the operation of our electric bilge pumps. I like to check the float switches are operational whenever I get a chance and this was a good time for a simulation of water ingress.

Electric bilge pump switches are one of those pieces of gear that can die silently and no one knows it has gone until needed. After checking the float switch was floating freely and working correctly electrically, I gave the guard screen around the switch a clean to remove the build of slimy goop that had started to grow around it. I am not sure where this sticky stuff comes from but it slowly builds up over time and can cause the float switch to become troublesome.

I left the hose dribbling into the bilge while I was cleaning the float switch that had been unclipped from its mount. The water level was rising so I had Deb manually run the electric pumps from the bilge pump control panel on the dash.

I washed the last of the suds into the pump before turning off the hose and had Deb stop the electric pumps. Everything looked good and the bilge was clear so I clipped the float switch back into position on its bracket before putting the floorboards back down and we carried on with our other jobs.

Later in the evening after seeing our friends off we headed to bed, however once in bed things just did not feel right so we got up to try and find the reason for the boat creaking and groaning.

In hindsight I think it was due to the bilge full of water having the boat settle onto the bottom as the tide went out. Not having heard these noises before we were looking around. Just out of curiosity I lifted the floorboards to have a look and was alarmed to find water lapping just under the sole.

We immediately set the electric pumps on manual run to clear the bilge, there was no time then to investigate why the float switch did not activate the pumps automatically. While we hear stories of time slowing down when in stressful situations, now the pumps seemed to be taking forever to make any headway.

While the electric pumps ran we spent several minutes looking for a leak, all the seacocks looked OK and the water level started to drop so we knew there was not a lot of water coming in.

Things were under control so we went looking for the large manual bilge pump handle so I could help the electric pumps. As it turned out the entire collection of manual bilge pump handles we had inherited with the boat were too short for efficient long time use of the pump.

While some handles did fit the mechanism and we were able to move the diaphragm, the problem experienced was the amount of work required to operate the pump. I was quickly tiring due to the effort required to operate the one gallon per stroke pump.

It is simple physics, the shorter the lever the higher the work required to move the load and, in the case of pumping bilges, it is moving the load, i.e. water, uphill. We had checked the manual bilge pump operation dry before taking the boat home but I did not unscrew the strainer and drop it into a bucket of water and pump water as I should have.

So my tip is to have a look at the leverage and handle pumping position of the manual bilge pump you have on board your boat with the outcome of the exercise to see how long you or one of the crew can physically pump the handle moving water before wearing out.

A very experienced sailor said to me that we should also check how easy it is to steer the boat and manually pump the bilges at the same time. Can one person do it or is it a two person job? After having a long handle made for our manual pump one person can now steer the boat and pump the bilges, leaving the other(s) to look for and minimise the source of the leak.

So how were our electric pumps configured? We had two electric bilge pumps: a small 360 gallon per hour (gph) and larger 2000gph. Both were run from a float switch that was connected to a three-way bilge pump control panel, configured: auto – off – manual.

We also had and still have a large volume manual pump. The manual pump moves approximately four litres (one US gallon) per stroke and, after checking the volume that can be moved, we found thirty strokes per minute is easily sustainable and should move approx. 7200 litres per hour (1850gph).

I am not sure why there was two electric pumps of different sizes, the smaller pump did not run on and clear any more water. I can only assume the previous owner installed two just to have another pump.

Three-way bilge pump control switch panels

If your boat does not come out on a trailer at the end of the day, my opinion for what it is worth would be to modify
it or get rid of it.

The electric bilge pump control we had was one of those panels with three-way switch position that has an off position;
I really have to question why a vessel that stays in the water has an off position for a bilge pump.

I do not want to be over-critical of the switch panel manufacturers. The pretty brochures advertising the switch panel are telling us what a wonderful idea it is to have the central off position for doing maintenance on the bilge pumps or float switch.

But come on guys, really, if we think about this when you need to service the pump and want the power off, simply remove the fuse that is right there on the panel. Do not have a switch that can be knocked or, for that matter, placed into the off position, it is flirting with danger. Another thing about most, admittedly not all, of these panels is there is no visual indication the pump circuit has power, the fuse could be blown and will go undetected.

During the evening in question and, as I have said the boat was relatively new to us, Deb was unaccustomed to the panel and did not know that leaving the switch in the central position disabled the float switch.

Having not paid any attention to the type of panel, I said after checking the pumps had cleared the bilge “that’s all good you can stop now” and that is exactly what happened, the switch was left in the off position.

What we think happened was that over the next couple of hours water trickled past a small piece of debris caught in the large bilge pumps non-return valve. With the pump control switch in the off position we did not have any idea the water level was getting higher and higher in the bilge, there was no visual indication or alarm.

A major oversight was that the large, electric centrifugal bilge pump did not have a vented loop to prevent back syphoning. The previous owner had installed a non-return valve to stop water flowing back in to the bilge, a definite no-no for this type of pump.

The rule is: unless the outlet skin fittings are well clear of the waterline, hoses need vented loops, a syphon breaker, with the vent fitted up high above the waterline no matter what angle of heel. So we had two faults, a lack of a syphon breaker and a non-return valve fitted in the outlet hose of the bilge pump.

A word of warning and I am surprised we did not have this problem: the next rule is that you should never plumb two bilge pumps into one outlet. If you have centrifugal pumps and one pump fails the water pressure from the good pump will force water back through the other pump losing valuable discharge volume.

On the subject of siyhon breaking, vented loops, recently I was talking with several people and it appears that there
is a general consensus of opinion that only toilets need vented loops and other hoses only need a loop, sometimes called
a gooseneck, up above the waterline.

Not having a vented loop is only OK if the outlet is well clear of the waterline on any angle of heel, so it is a worthwhile exercise having a look at your outlets. A new boat may have the outlet’s clear of the waterline when first launched, but load in a 100 metres of anchor chain, a large anchor, fill the water tanks add some spare parts, fuel and the family. Put the sails up on a windy day and, when heeled, check where the outlets are in relation to the waterline.

If the outlet does go under water you could find that while you are enjoying the breeze, the boat is slowly sinking when water starts to syphon into the bilge.

I have often noticed in some chandlery catalogues the vented loops are nowhere near the bilge pump or through hulls section but are bundled in the marine toilet section and appear to be called toilet vented loops. An oversight, but perhaps they should be in plumbing in their own section near the through hulls and skin fittings and called vented loops because they are not just for toilets.

Following up with our near miss I went and read the bilge pump manufacturers literature. The fitting instructions clearly state not to use a one-way valve in the discharge line but use a vented loop.

The installation drawings go on to explain a 300 millimetre minimum clear of the waterline without a syphon breaker is acceptable. As usual the drawing is a simple powerboat through-section and does not address the heeling characteristics of a sailing vessel.

Removing the one-way valve makes sense to me because I did do some experimenting and found the flap valve would not always open immediately when the pump started. On more than one occasion I had to cycle the pump to open the valve.

Considering the weight of water is almost nine kilograms contained in the 38mm x 8m of tube, it is a lot of force the pump has to exert on start up and, in all bilge pump applications, that weight of water has to be moved uphill as no bilges
I know of are above the waterline.

Keep in mind that some chandlery catalogues advertise one-way valves in the bilge pump section of the book. For proper operation of your system please read your pump manufacturers installation instructions carefully, there are some pumps that will benefit and others that will not work as intended with a valve installed.

Float switches

When we first took possession of our boat both float switches had failed; we found this during the checks prior to taking her to her new home. I guess I am now a little paranoid with bilge pumps and control circuits.

Check your float switches often and, if you have electronic sensor type switches, throw a bucket of water in the bilge to make sure they are working. Recently over sundowners I heard complaints from a couple of cruisers that if the sensors get oily they do not always work as intended.

From an environmental viewpoint some are designed not to pump oil, the reasoning is that no oil can be pumped over the side causing pollution. I do not have the full facts on the oil content in the bilges of the guys who made these comments to me about their switches not working. But, on the other hand, I have had people tell me they have never had a problem, no oil in the bilges? Perhaps.

Whatever type of bilge pump float/water level detection switch you have fitted to your boat they only work properly if kept clean. So check their condition visually from time to time and lift them, wet them, or submerge them to cycle the pump.
I give mine a cleanup with warm soapy water and going over with soft scrubbing brush to get off whatever it is that builds up on them so they work trouble free.

As soon as you can, after taking possession of your new boat, familiarise yourself with the safety gear including the bilge pump handles and operation. I thought I had the right pump handles. We had several manual bilge pump handles and
as it turned out none were exactly correct.

Also, if you need to open an inspection hatch to get to the manual bilge pump to operate it, get a couple of keys and tie one on a long lanyard in case you lose one and make sure the other is with the bilge pump handle.

Visually check your manual bilge pump, look for perished diaphragm(s) and then test the operation regularly by putting the end strainer in a bucket of water or throwing a bucket of water in the bilge and pumping it out over the side for no other reason than to check the bilge pump diaphragm is not perished, nothing is clogging the hoses and the valves have
not fallen off inside the pump.

I quickly modified the electric three-way bilge pump control switch so the float switch is never out of the circuit; if we needed to disarm the circuit we removed the fuse.

We have now made a new control panel with visual indication of pump and bilge conditions. We also have a secondary float switch circuit independent of the primary float switch circuit that will alarm visually and turn on a 100 decibel alarm if the bilge water depth level increases ten centimetres more than the primary float switch.

This secondary circuit will also switch on a relay to run the bilge pumps should the primary float switch fail. I have also installed a counter to keep track of pump run cycles; this works well because we found we had a very minor fresh waterhose leak that we were able to quickly track down before the tank completely emptied into the bilge.

I have installed a timer I brought from Jaycar electronics on the smaller pump circuit and it will run for a minute or more longer after the large pump switches off to clear the water that runs back out the hose of the larger pump when it shuts down. The extra run time of the smaller pump clears the last of the water from the bilge and without getting in there with a sponge and bucket there is usually only a tiny amount of water left in the bottom of the bilge.

Another safety feature we installed was a bilge pump power/bilge level/bilge pump run monitor in the cockpit; this gives us indication the power to the pump circuits is OK. It alerts us if the pump runs, as well as warning of bilge high water condition. A great safety feature when we are all out in the cockpit sailing along oblivious to what is happening below. We have heard stories from crewmembers climbing down companionway stairs into ankle deep water. It is certainly better to get early warning something is not right.

While we were coming to terms with our close call, a boat at our marina sunk, some of the locals were splitting hairs saying it did not really sink. But, in reality, it did sink. But because the tide was out, it sat on the mud and the dock kept it from falling over; enough water got in, however, to make a serious mess.

The discussion that evening at the yacht club was all about when a boat sinks when tied up at the marina. There was a lot of questions asked and opinions given but, through it all, the question most of us asked was “didn’t they have a bilge pump?”

So after thinking about it some more we all decided that while this is a good question, it is not completely the right question. Brain storming as you do when propping up the yacht club bar, we came to the conclusion that we need to look at this at a different angle. Perhaps the question should be how did enough water get into the boat quick enough for it to sink?

Water entering a boat makes it sink

There are lots of things that can quickly overrun a bilge pump, but common problems are putting a hole in the boat by colliding with something in the water and water ingress from a failed through hull is certainly another.

Connecting up a garden hose to the vessel as a way of having pressure water while tied up at the marina is another and has shown to be disastrous on a number of occasions. If a hose bursts and you are not there, it will be touch and go whether your boat sinks.

City water pressure and hose diameter plays a part and being at sea level the city water supply is usually at its best. Experiment next time you are tied alongside: while continuously supervising the water intake, place the dock side water hose in the bilge, turn it on and exercise your bilge pump system, then try and estimate how long your pump system will keep your boat afloat.

Because of the variables, this is something you will need to investigate and come to a conclusion with but, if it was me, I would not plumb in city water just for the convenience of not needing to fill the water tanks periodically.

The up side is, for that little bit of extra work you know the water in the tanks is fresh when you head out on the bay.

Once a boat starts to sink it is a compounding problem, with every extra millimetre of extra depth the hole is under water the quicker the flow of water will be: the more it sinks the quicker it sinks.

Check out the electric bilge pump capacities break out box with an overview of the larger electric bilge pumps on the market. I have listed the pump capacities as US gallons per hour because this is how they are marketed. One US gallon roughly equals 3.7854 litres.

The 4000gph unit draws 15.5 amps and is supposed to move 4000gph with no head when the batteries are fully charged. But, as with all electric pumps, when the batteries start to discharge the current draw increases due to the reduced voltage; the volume output of the pump also starts to decline due to the motor running slightly slower.

As you can see the largest DC electric pump, requiring the biggest battery capacity will not keep up with a 50mm hole just 300mm under the water, it would need to be supplemented with extra pumps, either a manual pump or motor driven pump or both.

What we know about bilge pumps is that the number printed on the outside of the pump is the volume of water the pump was able to move during test conditions in the laboratory. If we add pipe friction into the mix we reduce the theoretical water flow, the actual amount will vary due to pipe type and length. We will also need to factor in the head pressure and this can be substantial depending on how high the water needs to be lifted before it is pumped over the side.

The pump will require its own through hull fitting. Centrifugal pumps should not be fitted with valves on the discharge side as these will also slow the discharge volume. Do not plumb two centrifugal pumps in to one through hull, should one of the pumps stop, some (meaning: a lot) of water will circulate back through the failed pump. The other problem is the output will certainly be lower than what could be achieved with two through hull outlets.

So, as far as I can see, some of the best things you can do before heading offshore is to be prepared. Make sure all your seacocks and through hull fittings have emergency plugs attached by a short lanyard for immediate use, should the through hull fail.

When sizing the plugs do not just take the size measurement off the side of the seacock/ball valve and purchase a wood plug corresponding to that size, or you may well find the wood plug is too small when you need to use it. To get the right plug size head over to the seacock/through hull fitting section at the chandler with a plug and size them up. Check out the through hull size rough guide breakout box.

Also on the market are emergency flexible plugs that can be used on ragged sized holes. Become familiar with the different methods for stemming the flow of the incoming water. One of many I know of is simply a tarpaulin that can be deployed over the side, dragged into position and held there with ropes.

The pressure of the water on the tarpaulin makes an almost watertight se

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