A skin fitting (or through-hull fitting) is a reinforced pipe or component that penetrates a boat’s hull below the waterline, allowing water to enter (for cooling/intake) or exit (for sink/shower drainage) safely. They create a watertight seal and are crucial for plumbing, usually fitted with a shut-off valve (seacock).

Key Details About Skin Fittings:
Purpose: Provides a secure connection between the interior plumbing and the outside water.

Safety Requirements: Any skin fitting located below the waterline must have a seacock, which is a valve used to close the hole to prevent sinking.

Materials: Common materials include bronze, dezincification-resistant (DZR) brass, stainless steel, nylon, or composite plastics.

Installation: Installed by drilling a hole in the hull, applying marine sealant, pushing the fitting from the outside, and tightening with a nut/valve inside.

Maintenance: They should be checked for corrosion (especially checking for weak copper after zinc leaching) and blockages regularly.

Commonly found in marine shops, bronze skin fittings or composite fittings are recommended for their longevity, while DZR brass is often used, but normal brass should be avoided.