GROCO 1.25-Inch Stainless Extra-Long Thru-Hull Fitting

The GROCO THXL-1250-WS extra-long thru-hull is intended for installations where a standard-length fitting does not provide enough threaded reach through the hull or backing structure. A retaining nut is supplied so the fitting can be secured before the inside connection is completed. Its longer body gives the installer additional working length for thicker laminates, backing blocks, or mounting arrangements that need more thread engagement inside the vessel. The straight configuration works well when the connected valve or plumbing can align directly with the hull penetration.

The longer shank should not be treated as a substitute for proper backing or support; the hull-side installation still needs a sound, evenly loaded mounting surface. GROCO makes the THXL-1250-WS from 316 stainless steel and uses an NPSM/NPT combination thread on the extended body. Before final assembly, the installer can trim the plumbing layout around the actual available thread rather than forcing an undersized standard fitting to work. That thread arrangement is designed to work with compatible marine plumbing components while preserving the extra reach that defines this version.

• Straight layout for direct interior plumbing
• Retaining nut included
• Extended threaded body for thicker mounting sections
• Combination NPSM/NPT connection

Measure the complete hull and backing thickness before installing the THXL-1250-WS, then dry-fit the inside valve or adapter to confirm usable thread engagement. Bed the exterior flange evenly and support the connected plumbing so movement is not transferred into the hull penetration. Once the boat is in service, inspect the fitting and surrounding bedding for leakage or movement as part of normal below-waterline checks. For standard, extra-long, and specialty hull fittings, browse Thru-Hulls & Drains.