GROCO 2" #316 Stainless Steel NPS to NPT Flange Adapter

The GROCO 2" #316 Stainless Steel NPS to NPT Flange Adapter (Model IBVF-2000-S) eliminates one of the most dangerous problems in marine plumbing systems: thread mismatches between thru-hull fittings and inline seacock valves. When you screw a standard inline valve directly onto a thru-hull without proper adaptation, you risk thread stripping, leaks, and potential hull integrity failure—especially in rough seas or high-vibration environments. This flanged adapter solves that problem by accepting standard thru-hulls into its base while accommodating industry-standard inline valves on top, creating a secure, flush-mounted assembly that professionals rely on.

Manufactured from #316 stainless steel, this adapter provides superior corrosion resistance in saltwater, brackish, and freshwater environments. The 2-inch size matches the most common thru-hull and seacock diameters found on cruising sailboats, fishing vessels, and mid-sized recreational powerboats. NPS (National Pipe Straight) threads on the base accept thru-hull fittings, while NPT (National Pipe Tapered) threads on the top receive inline ball valves and gate valves. The flanged design distributes load evenly across the hull fitting, reducing stress concentration and vibration that can lead to fastener loosening or fitting failure over time.

This adapter is essential for vessel owners who use inline seacocks as primary through-hull isolation valves. It's particularly valuable for boats with older thru-hulls installed with straight pipe threads, or when retrofitting modern ball-valve seacocks to existing hulls. Weekend fishermen and offshore cruisers alike benefit from the safety margin it provides—a single fitting that transforms a potentially hazardous connection into a code-compliant, robust installation. The compact footprint (6" × 5" × 6") fits tight engine room and bilge spaces without requiring hull modifications.