GROCO 1-1/2" NPS NPT Combo Bronze Thru-Hull Fitting w/Nut

The GROCO 1-1/2" NPS NPT Combo Bronze Thru-Hull Fitting with Nut is a purpose-built marine through-hull assembly designed for reliable seawater applications where combination thread compatibility is essential. Cast from C83600 bronze, this fitting handles the demands of saltwater exposure while maintaining structural integrity under pressure, making it a dependable choice for both inboard and outboard plumbing systems on fishing vessels, cruising sailboats, and commercial marine operations.

The NPS/NPT dual-thread design accommodates both National Pipe Straight (NPS) and National Pipe Taper (NPT) connection points, reducing the need for multiple fittings in mixed-thread systems. This 1-1/2" diameter sizing positions the fitting for mid-range flow applications—suitable for bilge systems, raw water intake lines, and drainage circuits where higher volume throughput is required without over-sizing the hull penetration. The included nut provides secure deck-side or hull-side fastening, and the UL 647B listing confirms compliance with marine safety standards that govern through-hull assemblies. C83600 bronze resists dezincification and pitting better than softer copper alloys, extending service life in aggressive saltwater environments where galvanic corrosion remains a persistent concern.

This fitting is suited for boat builders, repair facilities, and experienced owners performing system upgrades or replacements on existing vessels. The combination thread configuration simplifies retrofits when original plumbing used mixed connection types. GROCO manufactures this fitting in sizes from 1/2" to 5", allowing builders to specify the exact bore needed without compromise. Stainless steel and BSPP (British Standard Pipe Parallel) variants are available for applications requiring alternative materials or international thread standards, though the bronze NPS/NPT model remains the standard choice for North American recreational and commercial marine installations.