Monday 16 January 2023

Bilge Pumps Basics

 Electric or Manual they are good to have on board. A discussion including how we almost sunk at the dock due to a dodgy bilge pump installation. We learnt a lesson and then wrote about it so share our feelings. I have also included some figures to give an idea on how bilge pump performance and how some times our vessels don't really have enough volume to clear a small hole. 

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 don’t 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 a little more with a hundred miles left to run before land fall. 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 don’t 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 wasn’t an easy job and required plenty of elbow grease because like a lot of boats, the bilges and under the floor board spaces hadn’t 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 fur balls 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’s 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 floor boards back down and we carried on with our other jobs.

The offending non return valve

Later in the evening after seeing our friends off we headed to bed, however once in bed things just didn’t feel right so we got up to try and find the reason for the boat creaking and groaning. In hind sight 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 and just out of curiosity I lifted the floor boards 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 didn’t 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 wasn’t 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. 

Bilge pump location to enable steering and pumping The handle is long enough to make the job physically easy

 I was quickly tiring due to the effort required to operate the 1 gallon per stroke pump. Its simple physics, the shorter the leaver the higher the work required to move the load and in the case of pumping bilges it’s moving the load, water, uphill. We had checked the manual bilge pump operation dry before taking the boat home but I didn’t 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 steer the boat and pump the bilges, leaving the other(s) to look for and minimize the source of the leak.

New bilge pump handle with the key to open the access port attached by lanyard

Keep the access ports well greased for easy opening

So how were our electric pumps configured? We had two electric bilge pumps a small 360 GPH and larger 2000 GPH and 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 1 US gallon (approx. 4 litres) 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 (1850 US GPH). I am not sure why there was two electric pumps of different sizes, the smaller pump didn’t run on and clear any more water. I can only assume the previous owner installed two just to have another pump.

Basic 3 way bilge pump switch with an off position of the switch. In a lot of cases the LEDs are so dim all the lights need to be off to see what selected. No matter what for safety a boat that stays in the water shouldn't have this type of pump control switch  

Three way bilge pump control switch panels, if your boat doesn’t 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; and I really have to question why a vessel that stays in the water has an off position for the bilge pump. I don’t want to be over critical of the switch panel manufactures. 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. Don’t have a switch that can be knocked or for that matter placed into the off position, its flirting with danger. Another thing about most (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 didn’t 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’s 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 didn’t have any idea the water level was getting higher and higher in the bilge, there was no visual indication or alarm.

Since our trials early on we fitted a panel in the cockpit to keep an eye on the operation of the pump when in the cockpit sailing along. 

A major over sight was that the large electric centrifugal bilge pump didn’t have a vented loop to prevent back siphoning. 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 outlets (skin fitting) are well clear of the water line, hoses need vented loops (siphon breaker) with the vent fitted up high above the water line 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, (I am surprised we didn’t 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 loosing valuable discharge volume.

Vented loop high up under the cockpit combing

On the subject of siphon 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 goose neck) up above the water line. Not having a vented loop is only ok if the outlet is well clear of the water line on any angle of heel, so it’s a worthwhile exercise having a look at your outlets. A new boat may have the out let’s clear of the water line when first launched, but load in a 100 meters 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 water line. If the outlet does go under water you could find that while you’re enjoying the breeze, the boat is slowly sinking when water starts to syphon into the bilge. I have often noticed in some chandlery catalogs 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 over sight, 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 manufactures literature. The fitting instructions clearly state not to use a one way valve in the discharge line but use a vented loop. Their installation drawings go on to explain 300mm minimum clear of the water line without a syphon breaker is acceptable. As usual the drawing is a simple power boat 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 9 kilograms contained in the 38 mm x 8 meters of tube, it’s 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 up hill (no bilges I know of are above the water line). Keep in mind that some chandlery catalogs advertise one way valves in the bilge pump section of their catalogue. For proper operation of your system please read your pump manufactures 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 don’t always work as intended. From an environmental view point some are designed not to pump oil, the reasoning is that no oil can be pumped over the side causing pollution. I don’t 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 clean up 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 familiarize 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 haven’t fallen off inside the pump.

I quickly modified the electric 3 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 10 cm 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 water hose 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’s happening below. We have heard stories of crew members climbing down the companion way stairs into ankle deep water. It’s certainly better to get early warning something is not right.

Bilge pump indication panel with cycle counter to keep an eye on how things are going. 

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 didn’t really sink. But in reality it did sink, but because the tide was out it sat on the mud the dock kept it from falling over, enough water got in 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’s 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 over run 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 a 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’re 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’re 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 wouldn’t 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.

The below table is an example of how much water will flood in from a through hull/seacock failure

50mm hole at 300mm = 078 GPM 4680 GPH 296 LPM 17,715 LPH

50mm hole at 600mm = 113 GPM 6780 GPH 427 LPM 25,665 LPH

50mm hole at 900mm = 136 GPM 8160 GPH 514 LPM 30,888 LPH

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.

Below is an over view 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. 1 US Gallon very roughly equals 3.785412 Litres

Electric bilge pump:

2000GPH 34 GPM 129 LPM

3700GPH 62 GPM 235 LPM

4000GPH 67 GPM 254 LPM

The 4000 GPH 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 50 mm hole just 300 mm 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 lab. 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 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. Don’t plumb two centrifugal pumps in to one through hull, should one of the pumps stop, some (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.

We have had the small bilge pump we use to clear the bilge go bad, so off to the chandlery we went and purchased a different brand but the same volume pump. What an eye opener when installed it was not able to lift the water enough to go through the vacuum breaker. The pump wasn't even operating to specs the lift was half a metre less than listed. So we returned the pump and the replacement was the same, again we went back to the shop and this time paid a little more and got the same brand pump we removed.  I must admit i was a little shocked with this as the pump that didn't work was a brand name pump not a cheap Chinese knock off with undersize motor etc. 

So as far as I can see some of the best things you can do before heading off shore 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 don’t 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.

But a rough guide of through hull sizes,

Through Hull Fitting Hole Size
3/4 “ = 1.041”
1” = 1.3”
1 ¼” = 1.65”
1 ½” = 1.9”
2” =2.35”

Assortment of emergency plugs

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 and dragged into position. The pressure of the water on the tarpaulin makes an almost water tight seal once over the hole, once the in flood of water is under control more substantial methods of patching the hull can be accessed.

Wood emergency plugs fitted to lanyards at the seacock hull penetrations. 

While electric pumps are great, don’t have them as your primary bilge pump, look more to having the electric pumps as supplementary pumps. When things start to go pear shaped usually several things happen in quick succession. After talking with a lot of cruisers it’s usually the batteries that suffer failure very quickly during a flooding. Well think about it, we keep our batteries down as low as we can to aid stability, so this area is the first to flood. Even if you do have sealed batteries they usually fail quickly as the terminals are corroded off the battery. Test your pumps on a reasonably regular basis. Test and clean the float switch(s) this is important to ensure the electric pumps will function when needed. I know the two pump switches I had that failed didn’t have mercury in side but had a steel ball to make contact should the float leaver rise, I guess the manufactures were trying to move away from mercury. Environmentally this is a great idea, but I am not sure if a steel ball was a good idea. This would have worked I think if they were sealed the contact tube better and purged with nitrogen to stop the rust when closed. When buying float switches it could be an idea to try and find out what kind of contact mechanism is inside. As a backup/alarm to my standard primary float switch, I have a bilge pump switch operated by air pressure, as water rises in the bilge, air pressure in the bell and air tube increases, operating a diaphragm switch in the unit and activating the pump. The good thing is that the electrical components are clear of the water and no sensitive electronics are used. The mercury free switch head means there is no environmental hazard should the switch fail. Something worth thinking about is a three way valve off your motor intake so you can select either the normal seawater intake or select water from the bilge, however you will need to make sure you have a good strainer on this pipe. Then clean your bilges on a regular basis so none of the pumps suck up anything to either damage the pump or stop it from working.

Hydro Air bilge pump switch doesn't need to be mounted in the bilge, this is in the electrics panel

If you can disassemble and inspect your pumps periodically looking for worn or damaged components. Pay special attention to neoprene or other soft rubbery parts such as diaphragms, flap/duckbill valves. This is not only good for preventive maintenance, it lets you learn how to disassemble and reassemble the pumps before an emergency occurs. For added safety pack a complete spare pump assembly, whether it’s a manual pump or electric. Being able to hot swap out a defective pump lets you quickly start to remove water again, this will allow you to repair the damaged pump later at your convenience. Stock a couple of bilge pump handles on lanyards so they can be secured and be quickly at your fingertips.

As a side note, most bilges can get small amounts of oil or diesel in the bilge water, and I do know most bilge pump rebuild kits offer two different types neoprene/rubber or nitrite. I go for the nitrite kit every time, they appear to last the same amount of time in use however if there is any oil or diesel or even WD40 for that matter in the bilge water the pump wont fail. I know some will say that should not happen and in most cases it it never will, but we are not talking about most cases, we are talking about disastrous things like a sharp log piercing the hull and damaging the fuel and or for that matter even breaking the sump on the motor.

So in conclusion don’t take your bilge pumps for granted, give them a little respect, and they will keep your bilge dry and maybe even keep your boat afloat long enough for you to figure out where that water's coming from!

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