Electric Bilge Pump With Magnetic Reed Switch

FYI, @Eric_in_Santa_Clara. I finished install of the electric bilge pump with a magnetic Reed Switch. As mentioned in the “Hand Held Pump” thread, I had an almost completed electric pump kit for a couple years - which includes, pump, hose, battery, waterproof case and waterproof plug in wiring/cable. Unfortunately, the on/off switch was right on the battery box. This is less than optimal since I think the switch should be on a reachable place on the external part of the hull.

I tried to find a rugged waterproof on/off switch. Surprisingly hard to find. The one I ordered from marine store turned out to be a “momentary” on/off switch (need constant pressure on the switch for the “on”). Looked for water proof magnetic switch but couldn’t find one.

Decided to try a glass reed switch wired with water proof connectors and shrink tubing. The reed switches I ordered from Amazon turned out to be rated for .5 amp. The pump was rated for up to almost 5 amp. That means I would have to some additional weird wiring with an additional relay transistor. That was the “complicated” wiring diagram you (or someone else) referenced from Gnarlydog’s site:

Given that I already had another switch on the battery box and then adding on a reed switch, the additional relay on Gnarlydog’s diagram was too much for my non-technical brain. I searched around and found a large Reed Switch rated for 6 amp at Ebay. I bought 3 of them (for other potential future project). This 6 amp Reed switch dwarfed the little .5 amp Reed switch I bought from Amazon.

Anyway, wiring the Reed switch in proved pretty straightforward, following along with the color coded wiring that was already done with the initial battery box switch. All to say, it’s pretty simple. I have wired several fishfinders/GPS with waterproof battery box, fuse, etc. It’s pretty similar to this except with the addition of the Reed switch integrated into power wire circuit. The water test yesterday in surf was successful.

Reed switch setup (to be glued underneath the deck where the bungee is) :

Battery box and pump:

Good luck if you decide to try. EBay for the 6 amp Reed switch.



PS. The bilge pump added on about 4 lbs to the kayak. Probably could cut off a one lb or slightly more if I switch out the lead battery with a smaller lithium. But, I won’t spend the money or time just yet.

I can feel the weight though. Normally, I can still lug the kayak without stopping the hundred yards plus from water’s edge to the car. Yesterday, I fell short my about 30 yards and put the boat down. The weight and the wind on the kayak were too much. (Someday, maybe soon, I am going to have to go with a kayak cart.)


I take it you didn’t want to drill a hole for one of these: https://www.amazon.com/DaierTek-Waterproof-Rocker-Switch-Lighted/dp/B07SGWXB3P
The only magnetic reed switch I’ve used was on a model rail car. Swipe the magnet on one side and it is closed, on the other side and it is open. Would be interested to know about the magnet you will use… tape it to the paddle shaft? And do you turn it off again by swiping in the other direction?

Saw that switch, but it said “weatherproof” and not waterproof. I am upside down in my kayak quite a bit in the surf zone and didn’t want to risk failure…

So, just as with the Reed switch, I found a 1.5" steel washer that I embedded into a piece of minicell foam. This too is cemented under the hull on the side, near the bungee deck fitting. The magnet is pretty strong and stays in place over the steel washer. I also encased the magnet inside a big bottle cap with epoxy. A small loop is also sticking of the epoxy with the magnet. The bungee runs through that loop in the epoxy. So, I slide the magnet from the resting area over the Reed switch, just in front of the mid section of the coaming, to engage the pump. I return the magnet back to the “holding place” when the pumping is done.

PS. The Reed switch I got is set to “normally open”. When the magnet is close by, in pulls the two metal tabs together to close the circuit. There are Reed switches that are “normally closed”. So, a nearby magnet would push the two metal tabs apart and opens up the the circuit (to stop electrical flow).


Didn’t realize it wasn’t a latching switch. Do you have to hold the magnet there to run it? Also did you coat the connections with sealant before using the heat shrink?

6a Reed Switch:

Waterproof electrical connectors:


Waterproof/silicon infused shrink tube:



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I see amazon has a few IP67 and IP68 rated submersible on/off switches.
Search on “IP67 IP68 submersible on off switch”, you might like “Hmknana IP67 Waterproof Inline Cord Switch 12V DC 20A”.
I also see some interesting IP67 options with unsealed terminals on the backside (?) … since you’re handy with epoxy, if you prefer one of those styles you could wire one up and pot out the backside to seal the connections.

Looks like the good stuff. I suspect you will need a way to hold the magnet over the switch until the cockpit is emptied. Might be just velcro.

Hi Sing, thanks for the project report, and the info on the reed switch operation and sourcing.

You mentioned using minicell foam ziptied to the reed switch assembly?

What adhesive are you planning to use for the underdeck mounting?

What is the function of the 1.5" washer? To shape/redistribute the magnetic field of the above deck bungee sliding magnet?


Here is the setup. Pump and battery box behind the seat. Through the hull hose fitting behind the seat (not in picture).

The white cap/magnet has a loop that slides back and forth along the bungee cord. The Reed switch glued halfway inder the bungee cord area. Slide the magnet along bungee to turn on Reed switch.

There is a steel washer embedded in minicell and glued under the deck next the deck fitting.

As you can see with black magnet, the washer serves as magnet docking station. You have to pull the magnet to release it from the dock. (BTW, the kayak is resting on its side on the hullavator. The untethered black magnet isn’t going anywhere.)


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One of these days I am going to put one in my canoe. I don’t do a lot of long continuous rapids where I need it, but when I do there is nothing worse than trying to run it with a boat full of water.

Sing, thanks for posting about the 6 amp reed switch. That’s a significant simplification from having to install a relay.

Like you, on the kayak I outfitted with reed switches, I embedded a magnet in a bottle top. I then drilled a hole through the magnet top so I could install it on the deck bungee. I think I got the idea from gnarlydog’s site, and you can see photos of the magnet on the bungee line there… Looks like you did something similar, only you installed a parking spot. I never had problems with accidentally triggering the pump on, so not sure how necessary, but it can’t hurt having the parking spot. Looks like a nice install. Where’d you put the hose outlet? Did you put a check valve? I imagine in surf you could have water going into the out-hole. Probably not a significant amount, eh?

I installed the magnet park because I don’t want to hear the magnet banging around in rough water conditions.

The hose outlet is behind the coaming, near one of the deck fittings. I didn’t install a check valve because of possible failure (freezing shut) in winter play (arguably when I may need backup of the electric bilge most!). Instead, I am just using a scupper plug to close the opening. It’s proven waterproof in the recent surf test. When I need to use the bilge, I need to twist around and pull the plug which has a retaining cord tied off to the deckline.


Encase the glass tube magnetic reed switch in epoxy but first of course solder the wires to it. I have used a electric bilge pump for about a decade now . I use a lipo battery that weigh 9 ounces and is 2.5 amps. Link to my setup here Kayak Bilge Pump Photo Gallery by Dan C. . at pbase.com
Both of the kayaks shown are long gone but have a pump setup in my newer kayaks a Valley Avocet and tiderace pace tour 17.


NIce. 9 ounces is about 1/3 the weight of my battery. Will go with that on the next pump.


HI, I just came across your post. A guy here in Australia sells “Magnetx” reed switch for mounting on the inside of the hull . The unit comes complete with the magnet,
, shock cord and mounts for the cord. I’ve now installed 2 and they work fine. I initially used a small sla battery but have since swapoed to using 8 rechargeable nii mih 1.2 volt batteries. Tests have emptied my 14-foot sit in three 3times and with power left.

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Sounds good! Post a link, please. I am sure some folks will rather pay a shipping premium rather than locate the components to build the circuit.


Sorry have been off air for a while, East coast Kayaking, in Sandringham, Victoria Australia, sell them. The contact ph no is 001161410 329 090, its a mobile number ( cell) their website is eastcoastkayaking.com.au. cheers Peter