30 April 2009

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)
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
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


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+...

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.


  1. I like your magnetic switch idea. I use a Water Witch electronic bilge switch that also works well, but is dependent on the water level inside the boat.
    Mark Sanders

  2. I wonder how hard it would be to find a waterproof switch that can handle the pump amperage, so you could remove the relay?

    1. Hi
      After a lot of searching I found a source of higher current magnetic reed switches which don't need a relay. They are made by HSI Sensing and I use model HSR-194W and it (or similar rated switches) are available via Koloona Industries (www.koloona.com.au) for about $8 and they will send them anywhere by normal mail. I have made several pumps using gnarlydogs basic design except withouthe relay. I soldered the ends of the reed switch on the positive wire and waterproofed it with sealant inside a length of heat-shrink which covered the whole switch tube and solder junctions. After attachment under the deck in a suitable position they work very well using a suitably placed magnet on the deck. The system is very simple and bomb-proof. The only problem has come from the magnets rusting, so make sure they are well sealed with epoxy or similar. Cheers... Roger

    2. Roger, thank you for sharing with other kayakers your findings. Fabricating the magnet and switch including the relay has been a sticky point for some folks wanting to have a reliable switch for the pump. Your suggestion will make things easier.
      Thank you.

  3. Telkwa, I did find some waterproof switches (rated IP67) but I had to buy a minimum of 10 switches.
    The swithces were from France.
    So far that was the only supplier that had anything that was durable, low profile and possibly reliable.
    While I cold have used eventually 10 switches (myself and friends) the single switch would end up costing almost $100.
    The alternative to an electrical waterproof switch would be an air switch used for kitchen sink garbage disposal.
    The switch is even more expensive (locally $130) and requires a rather big hole drilled in the deck to install.
    I also heard reports that in the heat of summer the air that is in the line expands and occasionally switches the pump on without the user knowing that. It can occur while transorting the kayak...
    A solution would be to disconnect the battery while car topping and reconnect before paddling, but that would be yet one more thing to remember to set up before launching.

    I would love to hear from anybody that knows of a better solution than the magnetic switch/relay set up.

  4. On my NDK Explorer LV I built a system which uses a standard wire skeg slider control to bring the magnet close to the reed. The skeg slider is to port, and the bilge pump slider is to starboard. The reed is fixed and encapsulated in epoxy in the recessed holder, and the magnet is in a hole drilled in the moveable knob on the slider. It works well. The rest of the system is the same as yours. Nick Crowhurst, Cornwall, UK.

  5. Nick, thank you for your idea.
    If you could send me a picture at gnarlydognews@gmail.com I will add it to the blog.

  6. Great article. I would love to see a pic of Nick's if he sent it to you. I am getting ready to do my NDK as well.

  7. Great article. What do you think of the Freedom 500 pump?

  8. Silbs, I believe Sea Kayaker Magazine has recently reviewed the Freedom 500 pump.
    Since the Freedom 500 is a direct copy of my findings (yes, the owner of the company copied to the letter my blog posting and then tried to patent it: http://gnarlydognews.blogspot.com/2010/09/bilge-pump-system-for-sea-kayakspatent.html) I think the set up should work.
    I have never seen one, only pictures.
    As long as the components are quality built (the reed switch has to be well sealed) and the wirings are soldered and sealed I can't see any difference than mine.
    It is however imperative that the battery box is 100% waterproof (Pelican cases are not) or it must be positioned in the day hatch, away from flooding.
    To date my system has given me, and others, trouble free performance. I hear that other installations were not so successful probably because of sloppy workmanship.
    There is a new option out now that does not need any switch, just pump and battery.
    I will install it probably in my new kayak, coming soon.

  9. Your articles are all extremely helpful. I am completing a wood strip kayak this spring and am planning to use an electric pump. I was getting ready to order the parts, but saw that you mentioned a new option without a switch. Do you have any particulars on it. I saw the freedom 500 and thought you had started production of your design, sorry to hear they stole it from you.

  10. Bill, I decided against the fully auto pump and went for the magnetic switch activated one again as described above. It has worked faultlessly so far in many kayaks, so, if it ain't broken don't fix it...
    For an auto pump look maybe at the Whale Supersub Smart 650. I find the ITT (Rule) auto pumps too big to be placed behind the seat.

  11. Why are we still putting these things together from a hodge podge of parts. Can't some company make an electric pump specifically for kayaks?

    These articles are all over the net. I have to admit I'm not clever enough to try any of them.

    I have no idea what a magnetic switch or a relay switch is. Moreover I don't care to know.

    For gawd sake, why doesn't some company just make a kit for this, it's 2011 not 1975.

  12. Anonymous, there is such company that sells the pump as a kit but it costs three times as much as getting the bits yourself. See this article:
    The problem with the kit is that it does not fit universally all kayaks the same way and some customization is necessary anyway.
    If one uses the new style of automated bilge pumps with integrated switches it gets pretty simple..

  13. I have just fitted out a new Point 65N XP18 with an arrangement similar to yours. Thanks for the useful tips. After looking at all the options I think your magnet switch is still the best one out there. I have also set mine up to allow charging a gps or mobile from the battery and to be able to recharge the battery with a small waterproof 4.5W solar panel.

    1. I have an xp18, and behind the seat, port side is a small flat area. Is that where you installed the outlet? Have you a picture or good description?

    2. I am not sure if Duncang will get your message but in the meantime I can suggest a solution to mount the pump anywhere you want it even if there is little room behind the seat. If you are inclined to do a bit of fibreglassing then you can check out this DIY: http://gnarlydognews.blogspot.com.au/2009/10/shop-recess-in-bulkhead.html

    3. I had thought of that intrusion into the bulkhead, to install the pump. I appreciate the link. In fact, the xp18 has enough clearance for the pump. My concern is simply the water outlet. If I follow the tradition of venting just aft of the cockpit, it's close enough for "splashback" into the cockpit. I assume, however, that I'll have the skirt on and be in the boat, so that's not really an issue. Because of the close tolerances behind the cockpit, port side, being very close to the rim, For this reason, I chose a fairly small outlet, which reduces the pump's 3/4" outlet to 1/2" at the deck outlet. I have considered punching through the bulkhead and installing the outlet via the deck over the day hatch zone. Has another xp18 owner mounted an outlet there?

  14. Just finished fitting an electric bilge pump into a Wilderness Systems Tsunami 165 using the magnetic reed switch config. The battery compartment I built from 90mm pvc stormwater pipe, a blank cap on one end and a screw cap on the other with a substantial rubber seal, its all waterproof and includes a 2 pin charging socket which saves me removing the battery. I am now putting another one in a Challenge Sequel.

  15. The PVC pipe is a good idea (and cheap).
    Thanx for sharing.

  16. Last year I installed an electric pump using your magnetic switch idea- works great. For my second kayak I tried to simplify the system by using an electronic switch. Bad idea the waterwitch switch I used drains the battery on standby. Without using the pump I get maybe one week out of my battery-I would advise against using electronic switches.

    1. Bummer about the Waterwitch draining the battery. Thanks for letting me know.

  17. My first attempt had a floating switch (reed, floating magnet). It worked but Because I forgot a main switch the pump started running when turned over i.e. on the roof of the car. The second one was with a electronic water sensor. The problem was that the sensor activated by salt water would not stop for the rest of the day, it kept activated on damp air.

    Waterproof hatches for fuse an recharging I used the top of a milkbottle. The mainswitch I covered with the top of a sodabottle. When you dont have to operate it on the water it is a very waterproof and cheap solution.

    My blog (in dutch) http://bjorri.nl/20080600/pomp.html

    Changed boat and stopt the project. Has any one tryed the http://www.aquachargepump.com/aboutaquachargemarine.html

  18. Can I ask why you believe silicone doesn't have it's place on a kayak?
    Thank you!

  19. My experience with silicone used as sealant or adhesive in sea kauakas is not positive. The silicone had poor adhesion. I now use polyurethane exclusively with excellent results.

  20. Hi,
    I have just descovered your site and have got to say that you have some great ideas. I plan to follow your instructions on installing a pump however do not have the technical knowledge to create the switch. Would it be possible for you to create said switch if people paid you for it.

    1. Nathan,
      Gnarlydog News only publishes my findings and opinions and is a commercial free entity.
      I do not sell or fabricate anything that you see on this blog for money. Occasionally I will make a sample for a friend, for free or cost.

  21. Firstly a sincere thank you for your original blog on installing an electric pump. I couldn't locate a suitable magnetic switch but found out thar Rule now sell an automatic version of the 500. I installed the automatic pump in a North Shore Atlantic which doesn't have enough room behind the seat. I installed the pump close to the front bulkhead and the battery and switches in the forward hold. I put the battery in a waterproof container with a standard bilge pump switch plate attached (continuous, off and manual settings). The pump cycles every 2 minutes when switched on continuous - only if it finds water will it continue to pump. I've never tested the maximum duration on a full charge but it definitely lasts for a long days paddle and can then empty the cockpit at the end of the day.

  22. Going to try install the Rule 500 25D pump with the setup described above in my NDK Greenlander Pro. I dont have much room as I removed my backband and installed a foam backrest that is glued to rear bulkhead. So no room directly behind seat. Have to put it to side in behind seat. It should get most of the water out and if I lean kayak too side to get all of the water. Now iam trying to decide on were to put the through hull connection. If I run it up front then I have to figure out how to get it by me without being in the way. If I exit it out behind me it would be easier.My question is you mention how you looped the hose to keep water from coming back into kayak. I cant really see that in the pictures and you also mention a check valve could be used. Has anyone tried a check valve and if so what kind and were did you get it. Iam in the USA so hoping to find one here.I have been looking online for a check valve but havent yet found one I think would work. Plus do they cause much flow restriction? If looping hose works ok maybe that will do ok. If I put through hull outlet in behind seat to side not much room to loop the hose.

    1. I have installed pumps INSIDE the foam backrest (http://gnarlydognews.blogspot.com.au/2010/01/shop-replacing-valley-seat.html).
      I carved a cavity large enough for the pump and then positioned the foam over the pump; works very well.
      About the loop: I found that it was causing cavitations sometimes and preventing the pump from picking up water and start pumping. The same was happening with the check valve. These days my pumps run a straight hose, no valve.
      To prevent water coming back in I have a simple cork in the outlet that I remove when I need to pump. My outlets are behind me high on the deck: shorter hose.

    2. Looking my NDK Greenlander Pro over more I don't think I can put the through the hull port at back as the deck is very flat the only spot I have were it would fit. I think it would both shower me with water and actually dump water back into the main compartment if I had it on while getting back into kayak. Plus I like to cowboy scramble which would put my leg right over the port while getting back in. Not that I plan to fail to roll. So I will put it up front which means putting a cork into port wont really work as I wont be able to reach it. I have found this check valve http://www.usplastic.com/catalog/item.aspx?itemid=23970&catid=489 that Iam going to test it out before I do anything to see if it will work. I have seen a few other videos on youtube were the exit port is up front and they don't seem to use anything to stop water from coming back up through port. Maybe the Rule pump wont allow water to come back up though it? Going to email Rule to see what they say, then test pump to see if water will back up though it. Thanks for the help.

    3. in my Rule 500 pumps there is nothing that prevents the water to flow back in if the pump is not turned on. I don't know how much pressure is (your link) "compact design with a 1/3 psi cracking pressure" in reality but if the pump is pushing only air at the start (before it picks up water) then maybe it can be too much to get it going. It's OK Once the water is flowing, it's getting it started with the impeller just drawing air that has caused occasional air locks in my set ups with check valve.

  23. This is a great idea! Thanks for spending the time to document it! I just made rudder pedals that feel/look more like surfski pedals so I couldn't figure out how to fit a foot operated pump and still keep good cockpit ergonomics.

    I saw a video on youtube of someone installing this and they just plugged the hole when not in use. I'd be curious how much water actually gets in while playing in the surf.

    Have you had any problems with sand causing clogging the pump?

    1. A little water does come in from the outlet if not plugged, but that all depends on how high above water is the outlet mounted and what are the size of the waves washing overboard.
      Sand has not caused me any trouble after years of pumping (just about all of my paddling is along sandy shores) but a small pebble has caused a jam once. I removed the pump's strainer and dislodged the pebble to get the pump going again.

  24. Hello, all. In 2011 I installed a Tsunami T-500 pump behind the back band in my Azul kayak. It was wired to a Big Foot trolling motor switch that I mounted on the forward bulkhead. The battery was behind the rear bulkhead in the day hatch. I used an SLA1056 battery I got from batteriesasap.com. The reason I used the Big Foot switch is because I didn't want to have to use a relay, just battery, motor and switch. And a fuse. It worked just fine until recently.

    Turns out the battery is shot. I'm not sure why. I was charging it with an automotive battery charger, which I understand is not ideal, but seemed to work. I'll have to order a new battery and will order the trickle charger when I do. I don't think my charge maintenance practices were ideal. Also, my day hatch used to take on water, so possibly the battery shorted itself to death.

    Regardless of what killed the battery, I tore my system up while trouble shooting. I suspected that switch failed, even though it was supposed to be submersible. But, bench testing showed it was still good. So, presently the switch is on the bench, and I hate working up there on the forward bulkhead. I'm ready to switch to the magnetic switch, but I'm having trouble finding the magnetic reed switch. I'd appreciate if somebody can provide a source. I find lots of alarm system switches, but they operate kind of backwards, completing the circuit when the magnet is removed.

    An aside: I've installed a system in my whitewater canoe. I think I succeeded in waterproofing my circuits and toggle switch, but am not using anything to keep water off the components. When the canoe is full, battery and everything else is submerged. This doesn't seem to affect the system, it continues to work well. But that boat has never tasted salt water, and I think that makes a huge difference. Just thought I'd throw that out there for anybody who doesn't take their boat in salt water--I think you can get away without the otter box, at least if you are not using a relay.


    1. Chip,
      my SLA batteries usually last about 2 years when I buy the cheap ones and a bit longer when I spring for a quality one.
      I understand that SLAs should not be drained totally before recharging but rather recharged regularly (for me that’s every couple of months).
      I had very bad luck with batteries that were not housed inside a waterproof box therefore ALL of my batteries are now in a Pelican box, and while not totally waterproof (submersion under pressure) they do the trick for occasional flooding (not in the cockpit but in the day hatch).
      My suggestion is that you revise your battery recharging habits and its waterproof location.

  25. I recently went out with uncaulked bulkheads--they were perfectly fitted and tighter than...the best laid plans of mice and men. My hatches flooded and there was no way I could reenter and use a Guzzler footpump. Downside: This pump only works in one configuration. Had my compartments not flooded..... but hulls do get breached don't they.
    Electric pumps have proved their reliability. Couple of questions: 1. would a NiMH battery be a better option than lead acid? What are your thoughts? Also would an 800 gph pump be even better? I do the math and all pumps (on paper) seem kinda slow. In practice they get the job done. (for the battery I'm going to look into portable drill batteries, easy to charge, the chargers are smart and I have a couple, I can cycle the batteries in the shop between paddles).
    The switch problem is tough. My experience with relays is that they can go bad, (pop! and they die) a switch would be best, but it would have to take the amps or it's going to fail a lot quicker than any relay.

    1. 1) I don't see why as Lead Acid ones are cheap, hold a charge well and relatively easy to charge. NiMH a bit lighter?
      2) some people install the 800gph Rule pump and works for them. Apparently they are more efficient however more expensive and a bit bulkier so might not fit in some kayaks? I never felt that the 500 was slow in emptying my kayak as the skirt is getting sucked down fast when the pump is running ( I have to open it and bump it or the suction is reduced)
      3) my battery needs a charge every 6 months so a set of batteries is for me redundant
      4) so far no relay has failed on me but there are also reed switches that are powerful enough not to need the relay. Other ideas for switches here: http://gnarlydognews.blogspot.com.au/2009/11/electric-bilge-pump-switch.html

  26. Well, I'm a bit further along in my journey.
    I bought a SuperSub submersible 650 gph auto pump. I plan to make it removable so I can transfer it between my two kayaks. I also plan to put the Pelican with the battery in the rear hatch, run the wire through the air hole in the center of my bulkhead. (So I'll need to make a watertight plug--probably something that I can close and seal in the Pelican opening.) Where to place the fuse?
    Definitely Sealed Lead Acid Batteries are less expensive than niMH and Nicad. I also have the experience that my 12 v and 18v cordless drill batteries don't last very long. My 9 volts last longer. I just ordered one. 3 AH.
    Question: SLA batteries can out gas hydrogen, is this a known problem? A pressure release would be good, I'm betting the Pelican cases would probably leak if pressurized from the inside--that's opposite to how they are expected to work. I also think leaving the pressure release slightly loose won't be a problem.
    Your site seems to be the best source of information. Are there any other?

    1. very interested to see how the SuperSub works out for you as I was contemplating it myself for future installs. Please let us know.
      The Pelican cases have a little valve that lets pressure out, that's why I use them with SLA batteries. 3Ah battery is overkill for general bilge pump duties unless you plan to use for charging other devices.
      I don't know of any other websites describing electric bilge pump installs off hand but the Sea Kayak Forum has some entries from others following my descriptions.

  27. Update on the Whale Supersub 650. I connected it to a 12V SLA battery (when I said 'cheap' I meant inexpensive--they seem really good). I've made the connections--not the best, but workable--nothing new here.
    The pump is nice, but the automatic feature is a little strange. I'm not sure how it senses the water. For tests it seems to turn on unpredictably, and pump dry for a while before turning off. (This is probably more noticeable to us kayakers than it would be in a larger boat).
    The shape of the Strum box (curved--but curved perpendicular to the kayak hull) leaves a lot of water in the cockpit--but not enough to slosh around and cause stability problems. (I do remember cold water rolling days not likely even a little water touching even my wet suited calves).
    I just drilled a hole 13/16 (the size of 1 / 2 PVC) and pushed through 3 / 4 inch pump hose from WestMarine (really great tubing). It seems to be enough to hold the pump in place--the pump is not loud, doesn’t have a torque kick.
    (If anyone doesn’t know about this pump hose, definitely check it out. it doesn’t crush, is light weight, and force fits onto 1 / 2 PVC very nicely.)
    I wanted a set-up that would allow me to simply connect the pump, strap down the battery box on the bottom of the cockpit. The hose, back-flow and spout stays in place. This way I can easily shift between my two kayaks, and not leave a colorful expensive piece of kit sitting in the cockpit.
    What I need to work on next is some kind of switch (right now it’s on the Pelican) and I’d like to find a more compact battery holder.
    What would really be great is a parts lists and sources. (I was going to order the toggle SPDT switches from Amazon, but they were going to take weeks. I studied battery sizes until I was cross eyed…). I found a nice switch for $5 at Pep Boys auto supply, but no waterproof boots yet.
    For wiring I just took a machine cord and cut the plug ends off. The Pelican is probably going to be took intrusive in the cockpit, so I’ll probably have to come up with a plug and unplug so I can store the battery in the rear hatch.
    Total cost is the pump, the pelican box, and about $20. There’s no way this should cost $600.

  28. I have read on various sea kayaking forums that you were considering using a Lithium Polymer battery for your pump. Have you experimented with this yet? Results? Lower weight is appealing but since it is something I do not understand and my chemistry days oh so many years ago imprinted in my mind that Lithium and water do not mix without violence, I am rather tenuous about their use. Clearly, many hobbyists use them in various wet conditons. I am curious about your results. In addition, I have read your posts advocated the 3 Amp reed switches without a relay. Are you using that system now or are you still using relays? Thank you for sharing your knowledge.

    1. I wanted more power for less weight, so I tried LiPo battery that I was going to recharge on-route with a solar panel (to recharge photo equip)
      I turned out that the controller alone to correctly charge the cells of the LiPo was rather cumbersome and very finicky: one little shadow (cloud) for a split of a second and I had to reset everything again.
      I ended up not using that system.
      I then tried a compact 12V LiPo battery (from eBay, China) and that thing did not have enough start-up current to kick over the bilge pump.
      And now I am back and still using the old trusted SLA: not light, low tech but incredibly reliable for me.

    2. Do you remember what size and how low-quality LiPo you tried? I'm currently using an SLA (for the same application) that is dying and would like to switch to lithium for all the benefits.

    3. I can't remember the capacity but I suspect it just didn't have the grunt to kick start the pump. After much debating and testing I am still convinced that the SLA strikes the best balance for value, simplify and reliability. LiPo works great for high intensity discharges, drones for example, but not really suitable for a bilge pump.

  29. from Hamish Jackson, Tasmania. I have a kayak (M580) I bought second hand with a magnet operated switch within the day hatch. I can't see a relay within the system, unless it buried within the casing that has been put over the reed switch. Anyway, it seems that the reed switch has broken (10 years old), since I find I cannot switch it off. I cannot seem to buy a reed switch to match the current draw of the bildge pump (same as yours), only 50mA reed switches. Any advice re: reed switch purchase, or trouble shooting magnet switch malfunction?

    1. Hamish, from what you describe maybe the reed switch never had a relay and the person that made it thought that one was not needed? that would explain why the switch would not open anymore and stay shut; it was overloaded. I sourced my higher current reed switches from USA and I might have a spare one. Send me a private email at gnarlydognews(at)gmail.com

  30. Thank you for a great article. I just finished sourcing the components for my first pump install and I thought you might be interested to know that I found a 3 amp reed switch on e-bay. They are General Electric catalog no M-282. I got four of them for about US$7.50 plus shipping from a seller in California.

  31. Hi. Well its 2019 so don't know if you will reply. But I have a similar system, but it's not working. The pump and the battery are OK, but the relay is not. But there are no specs on the relay. Do you know if there is a specific relay I should buy? Thanks in advance.

    1. Since the early days of including a relay in the switching of the pump I have found a magnetic switch that can take the current of the pump without the need for a relay. However a relay does still work, it just needs to be the right size (3A minimum)

  32. Thanks, managed to get it to work again, following your diagrams and links and the product number on the relay in your diagram. Found the same relay at Jaycar, and it soldered up OK. Also replaced the reed switch as it seems to have died, used one of these (minus the magnet as already have one) - https://www.jaycar.com.au/security-alarm-reed-switch/p/LA5072. Thanks for the blog. Chris

  33. I love tinkering with stuff and am really looking forward to installing my own electric pump. I realised the limitations of the hand pump when I capsized in (not even particularly rough) waters off Peel Island recently. I'm very grateful that you took the time to post such detailed instructions, thank you!

    1. thank you Innes. Bear in mind that an electric bilge pump is only good and functional if maintained and charged. The battery does discharge over time, even if not used and stuff does occasionally get stuck in the impeller. I would use it at least once per outing to make sure everything is OK because there is nothing worse than relying on a safety device to only find it failing in an emergency, as observed a few times on some kayaks. Happy paddling and may the wind be always behind you :-)

    2. Yes..wise advice. I see it as a backup to my hand pump - so that if it does fail there's no disaster. I have also ordered some solar panels by Wilderness Systems, to charge my W.S. Lithium battery (for phone, kindle, earbuds) whilst on the move. I bought a waterproof case big enough to accommodate two batteries. So we'll see if I can get all that to work. Do you have any experience with solar panels?

    3. I used to toy with solar panels and then I decided against them: too much bulk and futzing around for little return. None of my trips are really long enough that I need to recharge much more than a power bank can't handle (my main concern is digital camera batteries). On the occasional month long trip (Sweden) I did use a solar panel but it was kind of marginal. Now, if I did regularly embark on long expedition I would look into it further.

  34. Great site! I am new at this. I have a Cetus MV. I have purchased: PUMP:Rule 900gph/3407LPH 12v, 4A (needs 7.5A fuse) needs 1.3" water to turn on, with optional auto water sensing @2.5 minutes which I may not use. BATTERY: 12.8v 10A LiFePO4 (on sale $US55.). On-Off switch for deck mount APIELE waterproof round rocker toggle switch, 2 positions, DC12v, rated 20A,SPST, 3pins. BATTERY BOX: Elephant B09552 Kayak Battery Box ($US65 on Amazon) So, my QUESTIONS are: 1.battery box has internal 14AWG wire out to waterproof connection. But pump has 16AWG wiring. Is it OK to use just 16AWG after the battery box? 2. Do I need a relay (toggle switch says rted for 20A) and why? 3. given 7.5A fuse needed for pump, is that the only one I need in the system (there's a place for the fuse inside the battery box)? THANK YOU in advance for your advice!

  35. If the pump is positioned at the lowest part in the kayak (usually behind the seat) then 1.3" water is sufficient to turn it on and have an effective empty cockpit (bear in mind that the last bit probably needs to be sponged out, if you really want a totally dry environement). The Rule900 is a massive pump, good but a tad overkill and a bit more bulky than the 500. As for the switch I had no luck with toggle ones :-(

  36. Many thanks for your quick reply!
    I do have 2 wiring questions:
    The battery box has internal 14AWG wire out to the waterproof connection. But the pump has 16AWG wiring. Is it OK to use just 16AWG for everything outside the battery box?
    Do I need a relay? (toggle switch says rated for 20A).

    1. sorry can't help you there: my electrical knowledge is limited and the original set up of my pump was checked by an engineer at the time


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