I have written about the installation of an electric bilge pump in a sea kayak here.
While the install seems nothing out of the ordinary and has been done many times over by keen sea kayakers, the switch to activate the pump remains the sticky point for most installs.
The switch is also the culprit that gives electric bilge pumps the reputation for being unreliable.
I started off with the standard toggle switch that some kayak manufacturers (Mirage for example) use as factory install.
available in Australia at Whitworths
The switch is inexpensive and only a relatively small hole needs to be drilled through the deck of the kayak.
A rubber booth protects the internal moving parts and makes it waterproof.
Unfortunately the booth is prone to get a hole in it and inevitably the switch fails making the pump inoperable.
Often is the UV, the salt water or abrasion that hole the booth.
Replacing the booth frequently only limits the problems but not fully addresses it.
I have seen some installations of bilge pumps using an air switch that is commonly used in kitchen sink garbage disposals.
available at Costco
I have never used one but I hear that occasionally it switches the pump on without activation form the user. Apparently the air that is in the line from the button to the actual switch can expand in hot weather and trigger the pump. If not noticed (like during car top transport) it will flatten the battery.
The air switch is rather expensive (AU$130) and needs a large hole drilled on the deck to install the button. The button protrudes deep below deck.
I have been using a DIY magnetic switch that needs no holes drilled for its operation.
The switch is made of two 3 parts: the magnet, the reed and the relay.
magnet on deck reed switch encased in epoxy
The reed is the actual switch activated by the magnet and the relay is the "booster" that is needed to run the pump. The reed alone is not strong enough to run the bilge pump.
Since the magnet and the reed are totally enclosed in epoxy resin they are very durable and there are no parts to wear out or needing maintenance.
Some kayakers have been discouraged by the complexity of manufacturing a magnetic switch and have rather used the other alternatives or opted for a fully automatic bilge pump.
The commercially available automatic bilge pumps work on the principle of switching-on periodically (commonly every two minutes) and switching itself off if no resistance (water) is detected. Such pumps need to be connected to the battery before every paddle and disconnected afterwords, or the battery will run flat eventually by the intermittent activation of the pump.
Having the pump periodically switchig on for no reason (testing the "waters") while paddling can be annoying.These pumps usually cost 3 times as much as conventional electric bilge pumps and are bulkier making installs behind the seat in some cases not possible (there is not enough room).
There is also the option of automatic activation of the pump using a float switch.
When the water level in the cockpit of the kayak rises high enough to float the switch , the pump gets turned on.
Often these switches need a relatively high water level to turn on and occasionally fail.
A paddler will be sitting in a few inches of water before the pump goes off.
The float switch will also swtich-on if the kayak is turned upside down.
In a few cases the user forgot to switch the pump off while the kayak was inverted ending up with a flat battery.
Just recently I have come across a very neat small automatic switch that activates the pump by "detecting" water (available in Australia at Whitworths).
Witch Switch water sensor switch
The sensor will switch the pump on if it detects water covering it.
The witch switch can be installed in any position and low enough to activate the pump even lower water levels are present in the cockpit.
While I have not tried the switch (I am happy with my magnetic one) this unit sounds promising.
I guess it could be a good alternative for a pump install where the fabrication of the magnetic switch is just too daunting.
The company offers a 7 years warranty on the switch giving the user confidence in their product.
Rule does make a new automatically switched pump that uses the same technology in their switch but the pump will only activate at water level above 2-3/4" (70 mm).
The Rule Mate pump is also rather bulky and only kayaks with plenty of room behind the seat will accommodate its size.
The Witch Switch can be positioned to activate at much lower water level than that leaving a dryer cockpit.
PS:Steve Foreman has alerted me of this great option for an electric bilge pump set up. While I am a bit puzzled at all the electronic components (I am no engineer, obviously) it's good to see that there are options out there.