Electrical Bilge Pump for kayaks

Author: Holger

Category: Safety & navigation

Created on Wednesday, 24 February 2010 21:47

Written by Holger

If you ask a sea kayak instructor for the three most important things to take on a kayak trip he would probably answer:' a life vest, water and a bilge pump'. Interesting, a bilge pump.  Now you could argue that an Adventure Island is a 'sit on top', not a 'sit in' kayak, the cockpit is self draining, the hull is sealed, and it can't sink or take on water, therefore you don't need a bilge pump. In theory, you'd be right.

I thought so myself for a while. Unfortunately in real life that's not always the case. Things can, and do, go wrong. A while back I was on a trip with some friends, when one of us took on water - lot's of water. It was pure luck that this occurred on the way back to the beach and we reached the shore just before he went down. Had it happened 10 km off shore this situation would have been a disaster! The reason for the leak was a compromised seal at the rear hatch.

It became apparent to me, that I had to address this safety gap. Seeing as I already carry a 12V battery for my sounder the solution was obvious: I would install a 12V electrical bilge pump.

The pump: I settled on a Rule 500 which pumps 500 gallons ( = 1890 L ) per hour. Rule are renowned for their reliable and fully submersible bilge pumps at an affordable price. This pump is readily available, and probably the most common bilge pump used in kayaks. I also use the optional strainer to make sure the pump doesn't suck in small debris, which could potentially block it. The pump should be mounted on the lowest point inside the hull.  Because that is just behind the centre hatch, and a pump would be in the way there, I mounted mine a bit further back, just behind the seat. Be warned though, the mounting there is done blindly, and is a bit fiddly. The bottom part    ( blue ) is removable, which makes mounting a bit easier. After I ensured the pump was in the right position, I glued the blue bottom part down ( using a well known marine grade sealant ). Then, after an adequate drying period, I simply clipped the pump, with the pre installed hose, in.

The battery: I use a 12V, 9 AH battery fitted into an original Hobie gear bucket. The gear bucket fits the battery like a glove, the sealed lid keeps it all dry. Packed in the rear hatch, the battery is out of my way, and helps me to transfer some weight to the back of the kayak.

The switch: The switch is the part in the electrical system which is most likely to fail. Therefore, it is worth having a look into the different options available to switch & activate the pump. A very good summary of the different sorts of switches can be found here. I opted for a regular waterproof toggle switch, because it is cheap, readily available, and is a perfect fit in the hatch lid. One day I might upgrade to the magnetic system, but that means using a relay, more connectors, and more things that can corrode or go wrong if they are not well installed. I installed the switch inside the centre hatch. It fits perfectly into one of the 'squares' there, and requires no holes to be drilled. I figured that if the kayak feels like it's taking on water, I would open the hatch to have a look anyway, and then the switch is right there in case I need to switch the pump on.

The wiring should be done with great care to ensure it is 100% waterproof. I soldered every connection, generously applied sealant, and then put heatshrink tubing over it, making sure the sealant got squeezed out of both ends. The wiring path I used was: plus pole of the battery, sealed 2.5A fuse, switch, pump, out of the pump, directly to the minus pole of the battery.

The water outlet: I opted for a skin fitting with a plug. That is the only 100% waterproof solution I could find. Don't trust the non return valves. Rule advises against using one too, because of eventual airlocks. Non return valves rely on the weight of a water column pressing onto a membrane or ball to achieve a proper seal. I tried 3 different valves and all of them leaked when exposed to splashing. To find the right mounting point for the skin fitting took me a couple of days. A swamped kayak can become very unstable, so the outlet had to be within arms reach, to enable me to remove the plug. To get out of the seat or do anything else that would change the weight distribution was not an option. I wanted it to be easily accessible, above the waterline, facing up or away from me, and delivering the water overboard ( not into the cockpit or the well ).I didn't want it cluttering my cockpit, and it had to have enough room behind it to accommodate the fitting with the attached hose. This proved to be more difficult than I had first thought. I finally found the perfect spot: the centre handle. Placed here, it is protected from being knocked around, but easy to reach.

In the final test we swamped the kayak until it filled up, and I started to sink. After about 2 minutes of pumping I had regained a good amount of flotation and full control of my kayak, and after 4-5minutes the kayak was completely bailed out. A point to mention: After regaining enough flotation to open the centre hatch safely, it is best not to keep the hatch totally closed, but just slightly pushed down to allow some air to enter the hull, and avoid creating a vacuum against which the pump would have to work.

Parts needed:
Rule 500 bilge pump
Optional strainer for the bilge pump
Battery 12V
2.5 A sealed fuse
1m Hose 3/4”
2 hose clamps 3/4”
Skin fitting 3/4” with a plug
Sealed toggle switch
4m cable
Heatshrink tubing
Marine grade sealant