Quick links: Pump - Battery - Plumbing - One way valve? - Switch - Wiring - Operation - Notes

In lessons learnt from previous installations I'm trying out some new ideas. As backup I have a regular manual pump and sponge.

The Rule 500 is still the default choice. There are sophisticated versions that switch on and off automatically but I want manual control so the basic version is fine. I want the pump to be at the lowest point so its located behind the seat. When you need to pump out the dregs a forward stroke or two will slosh them towards the pump. The pump is quickly removable from its base which is glued to the hull by araldite (sand both first).

Last time I had a 2.2 AH version, to save weight and thinking along the lines that it's something thats rarely used, I've gone for the smaller Yuasa 1.3AH lead acid battery. The battery is located in the day hatch and attached to the bulkhead by sticky backed velcro.

The previous design involved a hose that had to be manoevered out of the cockpit and under the spray deck. This would be too fiddly in a tight situation so this time around it had to be a hole in the boat and a 'skin fitting'. I didn't want to put a hole in the hull around the cockpit region as that is an area of high stress / weak point in the structure of a kayak. I've built the output into the foredeck about 150mm forward of where my right knee fits, ie very visible and within reach. There are many 'skin fittings' on the market; I wanted a 90 degree fitting so that the outlet hose can run to the inside of the hull. Most fittings still protrude away from the hull too much for my liking so I modified the fitting I bought, cutting it short so there is minimum protrusion inside the hull. The other thing I didn't like about the fitting was it involved a constriction down to about 15mm diameter. The hose and pump outlet are 19mm. 'Waste' overflow fittings from plumbers merchants are 21.5mm. The solvent waste 90 degree bend has a considerably larger internal diameter and will allow better flow. When married up to the remains of the commercial skin fitting, the end result is flush, neat and will enable maximum throughput. There was about 0.5mm to make up between the 90 degree bend and the skin fitting, so a bit of insulation tape did the job. 1mm holes drilled in the edge of the nut, plus some corrosion resistant wire wrapping, ensured the 90 degree bend would not come free from the skin fitting. About 30mm of 21.5mm tube was glued into the 90 degree bend and the hose was forced over the tube with some silicon lubricant. The hose is self supporting to where it slots just beneath the cockpit rim and above the seat. It then curves around to the pump. It goes conveniently beneath where the knee touches the hull.

Some water may splash in through the outlet. Commercial one way valves can clog with sand and also are known to restrict the flow. I've used a bung made from medium density closed cell foam (e.g. old swim float or garden kneeler) with a 1mm string going through the centre, plastic washer and stopper knot and tied to the deck lines.

I think this is the trickiest part of the installation. Many different solutions have been implemented. I'm trying another 'blue sky' approach that bears some relation to my previous versions. It's built into the hatch cover of the pod so its directly in view, easy to access and its obvious whether its 'on' or 'off'. The two contacts are formed by the heads of two stainless steel pan head screws that are a tight fit through holes in the cover. The wires are attached to the underside and sandwiched between 'penny washers' (also greased with vaseline). The lever is built from a flat piece of stainless screwed and glued to a Maplins plastic control knob. Rotating clockwise covers both contacts and completes the circuit, anticlockwise breaks the circuit. The leading edge is raised slightly so it rises up over the screw heads easily, and the trailing edges drop down slightly to ensure the lever can't run over the screw heads completely. The only negative (scuse pun) consideration is that sea water conducts electricity but in trials this hasn't proved to be a problem.

The intention is to keep the number of components and wiring to a minimum. Where wires pass through bulkheads I've used Maplins smallest grommets. Holes have to be drilled to just the right diameter and the grommets can be fiddly to fit, its worth using silicone lubricant and practising on an old plastic container lid first. The negative wire goes high through the bulkhead behind the seat into the day compartment then to the battery. Extra wiring is needed - I found some wire in maplins that was a good fit in the grommets, this was HD speaker wire (500w). Best to get as thick as is practical to avoid any voltage drop over the length. In other words don't get wire that will just carry the current by its rating. The positive wire from the battery runs all the way to the switch. The return from the switch goes to the positive on the pump. Wires to the switch are taped to the outlet hose and just before the skin fitting they go into the 'pod' via grommets after which they're attached to the pod hatch cover. Spade terminals are soldered on and gently squashed a little to make a tight fit on the battery terminals and vaselined to prevent corrosion. The wires are taped across the top of the battery to avoid any movement and hence fatigue.

Presuming you are out of the boat and in the water:

All up weight of pump installation is ~1.5 kg
I've found a Wickes 22mm tank waste 90 degree fitting that looks good and will be trying that instead of the existing skin fitting.
For previous installations see here

Skin fitting showing bits used (top) and discarded (bottom).

Inside view of hose to skin fitting and switch wiring to pod.

Pump in situ.

Pump, backup bailer and sponge.

Switch and outlet.

Switch underside.