SHOP: electric bilge pump in a kayak

It is interesting how some technology seems to be more popular in one country than others.
Sails and electric bilge pumps are way more popular in Australia than anywhere else; skegged kayaks are more popular in Great Britain than Downunder or the Americas.
But let’s look at the bilge pump.
Like probably most kayakers, I equipped myself with the safety of a trusty hand bilge pump.
I really thought that with that piece of equipment I was ready to take on the rough seas.
I soon realized that even during practice the little pump was kind of, ahem..., a joke, if I was going to rely on it to empty my boat in case of a flooded cockpit in a serious emergency.
While the hand pump has still got its place in a sea kayak (empty a flooded hatch that by accident was left open?...) I don’t regard the little pump sufficient as main safety device.

How was I going to steady myself in my swamped cockpit and balance the kayak using both hands to operate the pump while waves were tossing me around?
It just does not work; not for me.

I am aware of two options for a hands free device that will empty water from the cockpit: a foot pump

commercialy available version


custom fabricated one with carbon

or an electric bilge pump.

I had a kayak with a foot pump and did not work for me. Maybe coz my big feet rub against the deck, maybe because I could not really steady myself while trying to balance the boat and pump with one foot or just because I found the foot pump so painfully slow.
I decided that an electric bilge pump will be my choice.
While certainly not totally foolproof it has a higher percentage of success rate than other devices.
To date I have installed 15 sea kayaks with the Rule 500 bilge pump.

If you are keen to install such pump in a kayak and are a bit handy with tinkering read on.

The pump is brilliant but the switch and installation pose some challenges.
Kayaks that have some room between the seat and the rear bulkhead are best suited to this install.

Components that you will need:

1) bilge pump (my preferred one is Rule 500)
2) Switch (including a small relay; will detail later)
3) Quality electrical wire (figure of eight)
4) Waterproof battery box
5) Small SLA battery
6) Outlet hose
7) Outlet spigot

For tools and supplies:

1) power drill
2) various drill bits (some small and a large one 10mm)
3) round file (or Dremel with attachments)
4) marine sealant (polyurethane, like Sikaflex)
5) soldering iron
6) heatshrink
7) epoxy resin (optional)

Before you start drilling try to suspend your kayak with slings. Working at waist height is easier and later on working inside the cockpit you can turn the kayak belly up and avoid a bad back.
Plan your install carefully considering thoughtfully the location of your outlet spigot, switch and hose route.
Think twice drill once.

The spigot outlet should be in a spot where it is not going to spray water on yourself or back into the cockpit. While it seems that I am stating the obvious I have seen some installs that made it happen. The outlet should also be above waterline, well above it.
The deck seems to be the obvious location.
Enlarge the hole with a file (or Dremel) just big enough for the spigot to fit snugly. No need to be sloppy.

The switch for the pump must be waterproof. I mean it. Electric bilge pumps fail most times because of lousy switches. I used to install pumps using the typical toggle switch with the rubber boot.

Good when new but the boot is prone to be torn or deteriorates in the elements.
I have seen air switches used but they cost a bomb and a large hole has to be drilled to install them.
To date the best solution seems to be a magnetic switch.

Ready made fully sealed burglar alarm switches are available from electronic parts stores but I have trouble envisioning the proper operation on the deck of a kayak.
I fabricate my own ones that require no holes drilled into the deck and so far have been very reliable. See appendix on how to make one.
More info on options available here.

The wiring has to be secured to the underdeck of the kayak. Loose wires will get ripped off while entering/exiting the kayak. It’s only a matter of time. I use polyurethane to secure the wires to the fiberglass inside the kayak.

The battery that powers the electric bilge pump is a 12V. Sealed Lead Acid (SLA) 1.3 Ah.
It almost fits perfectly inside the Pelican #1010. Since the battery is just a smidgen too wide a small section of the lining inside the box MUST be cut out to ensure a good seal when closed.
If you forego this step your box will not keep the water out.


The box needs a hole drilled where the wires will run to the battery.
Once the wires are in place I seal the hole with epoxy or high quality sealant (but never with silicone! It’s a product that has no place in a sea kayak, in my opinion).

Drill a small hole into the rear bulkhead behind the seat close to the deck. Run the wires to the switch and pump then seal with polyurethane.
The battery box is secured to the hull in the day hatch away from frequent dunkings.
Pelican boxes located in the cockpit have proven to leak.

I secure the bilge pump to the floor of the kayak with little saddles (custom made) and bungee cord. I heard some people gluing the pump directly to the hull.

Measure the outlet hose with a loop close to the deck and attached to the outlet spigot. While the loop will prevent water running back in, a quality non return valve can be used instead.
For kayaks with bulkhead too close to the seat to fit the pump, a recess for the pump can be created. Details here

Appendix:

THE SWITCH:
The switch is made of two parts: the magnet and the reed.
The reed is a little ampoule that contains a metal "leaf" that is "bent" by a magnet.
When you place a magnet over the reed it closes the circuit and makes the contact to activate the pump. Reeds are available from electronics parts stores.
The reed is soldered to the wire and then placed in a little section of PVC tube cut in half.
I use epoxy resin to encapsulate the reed and exposed soldering and make it waterproof.

Once the resin has cured I remove the switch from the mold and stick it with polyurethane (Sikaflex) to the underdeck (see previous image)

The magnet is made up of a small rare earth magnet (from electronic store) and a small piece of steel to channel the magnetism towards the reed switch.
(PS: further research revealed that the piece of steel is not really necessary. The magnetism of the rare earth magnet is not really shielded by such a small piece of steel. Future magnetic sliders willbe made without the steel bit)
I position the rare earth magnet in a suitable plastic cap (or mold) .
I place a spacer of thin paper under the magnet. It will allow for clearance of the hole where the bungee cord goes.
Make sure that the resin covers all the components or salt water will corrode them in no time.

visible are rare earth magnet on top of section of steel (PS steel not really necessary)
The little reed switch is not strong enough to operate the bilge pump.
It needs a booster: a relay.
The relay must be strong enough to switch the pump (minimum 3 A). Below relay available from Jaycar.

A typical diagram for the wiring will look like this. This wiring will only work with this relay. Other relays will need a specific wiring depending on the design of the part.

The above diagram does not show a fuse (strongly recommended)
The relay (and fuse) are positioned in line with the positive (+) and are all contained inside the Pelican box inside the day hatch of the kayak.

The local kayak outfitter charges $395 for fitting an electric bilge pump in your kayak.
If tinkering does not scare you probably you can save yourself about $250+...

PS MAR'10
Douglas Wilcox from Seakayakphoto has installed a Rule 500 fully automatic pump for jetskis (25S-6WC).
He does not use any switches, fuses or relays. The pump turns on automatically every 20 sec and it continues to pumps only if encounters resistance (water).
According to his findings he used the pump on a 10 day trip having it connected every day and emptied a flooded cockpit at least 10 times.
There was plenty of power left in a 1.3 Ah SLA battery.
He does not use a waterproof case either (battery in day hatch) but simply connects to the battery terminals with spade style connectors.
After a few years of use he is confident that his set up is very reliable.