Skin fittings and seacocks explained

Surveyor Nick Vass examines different skin fittings and seacocks on the market and shares advice on maintenance

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Yacht design demands a compromise between form and function, between reducing holes that could sink and perforated topsides that would look ugly. Discharges fitted to the topsides leave unsightly stains from sinks, rusty, oily, sooty exhausts, rusty anchor chains and limescale from water tank vents.

Yet boats need to have holes through their hulls to allow air and water in and out. It's best if as many as possible are above the waterline for obvious reasons, but the toilet inlet and engine coolant intakes must be below. Toilets discharge below the waterline to avoid stinky embarrassment, while speed log and depth sounder transducer would be useless above the waterline.

Any discharge, vent, air intake or drain above the waterline must have a hose or baffle moulding that extends as high as possible above the weather deck.

Draining anchor and gas bottle lockers must be watertight and separate from the inside of the hull to avoid flooding and poisoning. Bilge pump outlet hoses must be kept as short as possible, as a long hose greatly reduces the litres that you can pump per minute, while at the same time, the discharge hose must be formed into a high anti-siphon.