Every hose on a seacock or through-hull below the waterline is held on by its clamps. When a clamp rusts through, the hose can slip off the tail and the sea comes in at the full size of the fitting. It's one of the cheapest fixes on a survey report and one of the most argued about.
What the standard asks
Less than many people think. BoatTEST's Jeff Hammond says ABYC H-27, which covers seacocks and through-hulls, contains no general double-clamp requirement, and that the US federal rules don't address through-hull clamps at all. A raw water intake on a seacock with one clamp is technically compliant.
ABYC does require two clamps in two places, as Practical Sailor and BoatTEST both set out: every exhaust hose connection, with all-stainless clamps not relying on spring tension, and fuel fill hoses. Practical Sailor adds that sanitation hoses should be double clamped.
Hammond's view of the surveyor who flags single clamps below the waterline: technically incorrect on the standard, completely correct on safety. So write it as a recommendation, and say so.
How a surveyor checks it
Follow every hose from a seacock or through-hull, plus the exhaust and fuel fill. At each clamp:
- Count them. Two on exhaust and fuel fills. One or two elsewhere, noted.
- Check the metal. Practical Sailor says look for all-stainless construction and watch for plain steel screws. Hammond notes stainless clamps can and do rust. Look closely at the band where it passes the screw.
- Check the fit. The tail has to be long enough for both bands. Hammond warns a second clamp past the end of the barb distorts and crushes the hose. Practical Sailor says sharp or damaged barbs are a common source of leaks.
What decides the grade
A corroded or broken clamp below the waterline, or a single clamp where ABYC requires two, is an A. Single clamps on sound below-waterline hoses, or clamps with steel screws, are a B. Sound clamps poorly placed are a C.