Through-Hull Fittings — DZR Brass & Silicon Bronze

Through-hull fittings provide the watertight passage between the hull interior and the sea outside, used for engine raw-water intake, raw-water discharge from engine cooling, sink and head drains, bilge pump discharge, and instrument transducer mounts on small craft and commercial vessels. Below-waterline through-hulls are subject to constant immersion in seawater, frequent thermal cycling, and dezincification corrosion that destroys standard C36000 brass within 5-15 years of installation. Our below-waterline through-hulls are manufactured from two corrosion-resistant alloys: Dezincification-Resistant (DZR) brass conforming to CW602N specification (the European marine industry standard for below-waterline brass), and C65500 silicon bronze (96% copper, 4% silicon — the historic marine standard with the longest field service track record).

Both alloys are fully compliant with ABYC Standard P-1 requirements for below-waterline metal components. Standard sizes range from 3/4" through 2" pipe size, with the inboard end threaded NPT (or BSP on request) for the matching sea cock, and the outboard end shaped as a hose barb sized to match standard marine hose ID. Mushroom-head flange variants are available for transducer mounts and applications requiring a flush external profile.

Each fitting is sized to receive a backing plate (we supply matching ABS or G10 fiberglass backing plates on request) and is electrically bonded to the vessel's negative bus per ABYC E-2 corrosion-protection requirements. Production includes 100% pressure testing in the partner facility's QC lab. NMMA certification documentation supplied for OEM boat builders. MOQ 200 pieces; lead time 6-10 weeks.