Bilge drainage - Water, water everywhere but not in your multihull

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Water in the bilges brings nothing but trouble: not just moisture, corrosion or mold on board, but also damage to the equipment that is situated under the floors - starting with the hulls themselves, whether painted or not. If the bailer and bucket were the first tools to fight flooding, the first bilge pump was invented by Archimedes as far back as 270 BCE. It was a screw pump that was manually operated. Today, despite the adoption of watertight materials such as polyester or aluminum, boats still manage to get water in them. The fault lies with the very numerous openings such as those for the motors, or cockpit drains, transducers and any throughbolted fittings. The shallow bilges of most multihulls - often without a sump - increase the risk of water collecting, thus making bilge pumps even more essential. They also become your best allies in the event of water ingress: thanks to their action, you will have time to plug any ingress or, in the worst-case scenario, to prepare for abandoning ship

Oops, the water is starting to rise... In this very well-equipped bilge, there’s no way we’re going to let the water rise. Two level switches operate two pumps: it’s the least that you should do.


But the biggest danger is when you’re not there - more boats sink in harbor than on the open sea. Water can accumulate on board surreptitiously due to condensation, small leaks - external seals, hose connections below the waterline - or even a deck hatch that has been left open or is broken. Good ventilation may be sufficient to dry the bilges of any normal condensation, but if the volume of water is large, pumping it out becomes essential to prevent the level from becoming critical. For small multihulls, one pump can work on two hulls or compartments, but it is advisable to provide a three-way valve to stop the evacuation of a hull already that has already been drained and to concentrate pumping efforts where necessary. On a larger multihull, each watertight compartment or hull has its own pump. Each bilge pump is fitted with a strainer: one of the main reasons for the failure of bilge pumps is the presence of solid objects such as grains of sand, debris or dirt in the pumping circuit. These particles eventually damage the moving components of the pump such as the impeller, centrifuge or possibly the diaphragm. A pump should be placed at the lowest point on the inside of the multihull where water is likely to accumulate. It must remain easily accessible for maintenance or servicing. Bilge pumps are classified into two main categories: Manual or electric.

Doubling the securing of fittings below the waterline is a useful precaution. Ideally, a mini sump like the one shown here on board the Excess 12 allows you to place the pump in it and prevent standing water in the bilges.


A manual de-watering device (scoops, buckets or hand pumps) is usually mandatory, but may not be ...

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