Plastic Thru-Hull Hose Fittings (White) – Ø15 mm to Ø38 mm

These white plastic thru-hull fittings are fundamental components of any boat’s drainage or venting system. Their design is simple and reliable – a threaded tubular body with a wide outer flange and a locking nut that secures from the inside. They come in five standard sizes (Ø15, Ø18, Ø25, Ø32, Ø38 mm), covering needs from the smallest drain lines to large-diameter scuppers. The white plastic blends aesthetically with most hulls and decks. The material resists saltwater and UV exposure, ensuring the fitting won’t crack, discolor, or corrode over time.

• Ø15 mm: A small fitting suitable for narrow hoses – for example, the outlet of a tiny bilge pump (around 500 GPH), draining water from storage compartments, or acting as a vent for a fuel tank. Recommended for smaller boats and jet skis where the drainage flow required is minimal
• Ø18 mm (3/4″): A very common size for standard bilge pumps (600–800 GPH) and general drains. Ideal for routing water from a small bilge, a shower drain in a cabin, or as a discharge for a cooling system. Widely used on boats about 4–6 m in length
• Ø25 mm (1″): One of the most popular sizes. Used for medium-capacity bilge pumps (800–1100 GPH), draining shower sumps or sinks, and general bilge water discharge. An excellent choice for boats in the 5–7 m range where a greater flow rate is needed for dewatering
• Ø32 mm (1¼″): A larger diameter suitable for higher flow situations. For example, as a vent for water or fuel tanks, an outlet for a marine toilet or a high-volume pump, and for bigger boats (~7–9 m). It provides fast removal of water or air without bottlenecking
• Ø38 mm (1½″): The largest size available, perfect for main deck drains and cockpit scuppers on big boats (8–10+ m). This size handles very large volumes – for instance, rapidly draining a cockpit during heavy rain or emptying a baitwell or livewell. It’s also often used for the intake/outlet of raw-water systems (e.g., engine cooling) due to its capacity

All these thru-hull fittings install with the same straightforward procedure: drill a hole to match the threaded neck, insert the fitting (with the flange on the outside of the hull), then tighten the backing nut from the inside. For a watertight seal, you can apply a marine sealant under the flange before tightening. The result is a secure, leak-free pass-through that allows a hose to carry fluids out of the boat. The plastic construction is maintenance-free, but it’s good practice to periodically inspect the seal around the flange – especially for the larger diameters where the flow pressure can be higher – to ensure everything remains tight and dry.