GROCO 1-1/4" NPS NPT Combo Stainless Steel Thru-Hull Fitting w/Nut

The GROCO 1-1/4" NPS NPT Combo Stainless Steel Thru-Hull Fitting with Nut is purpose-built for serious boaters and anglers who demand reliability below the waterline. Whether you're installing raw-water cooling systems, baitwell intakes, or through-hull applications on fishing vessels and cruising boats, this fitting delivers the corrosion resistance and thread versatility that saltwater and freshwater operators depend on. After years on the water, you know that thru-hull fittings are non-negotiable—they're the unsung heroes that keep water flowing where it needs to go without compromising hull integrity.

Constructed from #316 stainless steel, this fitting resists rust and galvanic corrosion far better than lower-grade alternatives, ensuring longevity in harsh marine environments. The combo NPSM/NPT thread design provides dual compatibility—allowing you to adapt to both National Pipe Straight Mechanical and National Pipe Taper connections without sourcing multiple fittings. UL Listed under 647B certification confirms its suitability for marine plumbing and through-hull applications. The included nut ensures a secure, watertight seal, while the 1-1/4" bore supports adequate flow rates for cooling systems, livewell pumps, and bilge applications common on mid-size and larger vessels.

This fitting excels for retrofit work and new builds alike, whether you're upgrading aging thru-hulls or installing systems from the ground up. Experienced installers appreciate the dual-thread design when working with mixed manifold configurations or when original specs call for different thread standards. Installation requires standard marine sealant and proper bedding technique—use quality 5200 or equivalent to ensure the seal holds. Compatible with standard 1-1/4" hose barbs and compression fittings, this GROCO unit integrates seamlessly into both raw-water and closed-loop systems on center consoles, sport fishermen, cruisers, and commercial vessels.