Why install an electric pump? well I wasnt too keen on the hand pumps that need both hands to operate, the Tasmanians have been using them for years and swear by them (google Maatsuyker) and its undoubtedly the quickest way to empty a boat in a hurry. But there's no denying that an electric pump setup is complex and of all the installations I've seen there appeared to be issues either in getting the right bits of equipment or whether they would work in my kayak.
Pictures are at the end of the write up. I've tried it out for the first time recently and it seemed to work very well. Will continue testing throughout the year to see if any improvements are necessary.
Design considerations
I looked at a number installations in the guidebook and other websites and in some kayaks belonging to fellow paddlers. I favoured a modular approach and with minimum impact on the kayak. By that I mean using readily available components, being able to replace those components easily and not making the installation permanently dependent on any one component. Additionally the kayak itself imposed limitations on the location of components.
Pump: There are a number of reliable pumps on the market; no obvious issues here.
Battery: Plenty of choice available in terms of capacity, weight & price; again no obvious issues here.
Wiring: Wiring connectors and fuses readily available (but need to consider effects of water).
Switch: This is where things get complicated. Waterproof switch? which switch to purchase, waterproofing? where to locate on the kayak etc. Air pressure driven switches etc. Simple in concept and operation but in the watery environment not so simple.
Outlet: A fundamental issue. If its in the side of the kayak its near the waterline and water and sand is going to get in. Pumps are typically of the impeller variety and water can backflow through them easily. Hence if the outlet is near the waterline some sort of valve is essential. Another choice is to have the outlet in the deck somewhere but there is always the possibility that water may still find its way back in.
Non return valve: A logical choice. Several choices available but two typical problems; firstly the one way seal may be compromised by sand and secondly the outgoing water flow can be restricted by the valves mechanism and dimensions.
Vacuum: The pump is likely to be used in some sort of emergency situation and this is likely to be in rough water conditions. The spraydeck needs to be put back on as soon as possible to prevent further water getting splashed in. But if your spraydeck is a good watertight fit it will be almost airtight as well. Air needs to get back into the main compartment to replace the water that is being pumped out.
Solution
I've come up with a solution that solves a number of the main design considerations in one go. This is the main feature of the installation; the outlet, switch and non return valve are all combined in a unique way.
Outlet / switch / non return valve / vacuum
There is no outlet hole in the hull, no non return valve, no obvious switch and no vacuum problem!
A length of plastic pipe is connected to the pump outlet. This goes behind the seat and then curves around into the area in front of the seat.
A piece of stainless steel (SS) pipe is inserted into the end of the plastic pipe. A wire is soldered to the SS tube and the wire goes inside the plastic pipe back to the pump but exits the plastic pipe just before the pump. The wire is finally connected back to the +ve side of the battery. This forms one half of 'the switch'.
On the side of the cockpit coaming is an opened out piece of SS tube that is shaped to fit the cockpit coaming and is attached to it by a couple of small SS bolts. At the back of one of these is a wire that is connected back to the -ve side of the battery. This forms the other half of 'the switch'.
To activate the pump you put the spraydeck on but trap the SS tube end of the outlet pipe between the spraydeck and the cockpit coaming. The pipe comes up between your legs. This effectively closes the switch and the pump starts. The way in which the spraydeck fits over the tube allows an airgap each side of the tube which permits air to get back in to replace the water thats being pumped out. As soon as the pump out is complete you simply push the pipe back inside the boat, 'switching the pump off' and fit the last bit of spraydeck.
Although several functional features are combined its actually a very simple lo-tech piece of kit that seems very unlikely to fail. The point of failure is most likely in the usability hence I'll be doing a lot of testing.
Pump
I chose the Rule 500 pump (12v), its seems to offer a good reputation and high performance for its size. It sits directly on the floor of the kayak and I've put it behind the seat to one side. In my Alaw Bach this seemed like the only obvious position. Being to one side when you're near the end of pumping out you need to lean slightly to one side to get the maximum out of the boat. When the pump starts sucking air a few waves are welcome to slosh the water around the pump, once air starts getting sucked in its hard to get the last few dregs out. The pump is not actually anchored, a piece of bent aluminium with foam stuck on it is attached to the base of the seat and holds the pump in situ. To get the pump out all I need to do is to slide the seat forward.
Battery & wiring
I chose a lead acid 2.2 amp hours battery (12v) from Maplins. Easily replaceable in different capacities. The battery is located in the day compartment which I consider to be a 'dry' environment. Two 'only just big enough' holes are drilled through the bulkhead (high up) and the wires go through these with silicone sealant both sides. A one amp inline fuse is wired into the positive lead right next to the battery. All spade connectors and contacts are 'vaselined'. Connections in the main compartment are taped over with insulation tape. For the actual wires get thick rather than thin to minimise power loss. So far I haven't fixed the battery within the day compartment, its wrapped up in some plumbers pipe foam insulation with rubber bands and is free to move around inside the compartment. On the Alaw Bach the compartment is fairly shallow and getting stuff in is a bit of a squeeze so I may leave it like that otherwise I'll arrange some form of bungee mounting.
Notes
I found a piece of SS tube that was malleable (matt finish) and made a good electrical contact. I soldered the wire to it using a blowlamp (carefully).
Where the wire exits the plastic pipe just before the pump there is potential for a bit of leakage but if it occurrs it'll be very small compared with the amount of water getting pumped.
No non return valve means the pump can work at maximum efficiency. A full compartment pump out takes approximately 3 minutes. This is a guess, I will time it.
The contact plate on the cockpit coaming was cut and beaten out from a piece of pipe hence it looks a bit odd in the pictures with all the cuts that were necessary to make it conform to the 3D shape of the coaming. Room for improvement here. The edges are taped to ensure no clothing gets snagged.
The contact ('switch') between the SS tube end and plate on the cockpit coaming seems to work very well. Due to the curved shape of the contact and its length a considerable variation of positions is possible and contact is still made.
The way in which the spraydeck can happily stay on with the SS tube pinned between the spraydeck and the coaming may not work on all cockpit shapes, ie I couldnt imagine it working with an 'ocean' style cockpit.
The pipe lays happily on the floor of the main compartment and doesnt seem to get in the way at all.
Problems
Pumping out removes about 95% of the water - there's always some dregs that the pump cant quite get as its sucking mainly air at the end of a pump out. In this situation a design flaw has come to light - electric shocks! ie if the pipe end is in the bottom of the boat in contact with the water a circuit is made through everything else thats wet (ie wetsuit outer). The 'switch' mechanism is going to be redesigned.
Fix
I've added an enhancement to the stainless pipe at the end of the plastic hose in the form of a piece plastic pipe that fits over the stainless tube. A small piece at the end of the stainless tube is bent up into the slot to prevent the plastic sleeve sliding all the way off. The plastic sleeve is pulled out to expose the bare metal tube to make contact with the plate on the cockpit rim. When the pipe is not in use in the boat its positioned so the end is resting vertically upwards well out of contact with any surplus water sloshing around in the boat.
Pictures
Pump located behind the seat in the corner. Note +ve wire exit from plastic pipe.
Pump close up. Note bracket holding pump in place and pump sitting on kayak floor.
Outlet pipe routing around side of seat.
Outlet pipe resting on main compartment floor ready to use. Note stainless steel end on pipe and stainless steel contact on cockpit coaming.
Battery up close showing in line fuse.
Battery in situ with foam wrapper and wires going through bulkhead high up and sealed.
Outlet in working position pinned between spraydeck and coaming and contact being made so pump is 'on'. Note also airgap each side of tube.
Enhancement at the end of the outlet pipe; plastic tube covering stainless steel tube.
Plastic tube extended to expose stainless steel tube.
Switch version 2 at the end of the outlet pipe; plastic tube covering stainless steel tube.
With both wires inside the plastic tube and contact at the end of the white plastic.
