Flexible Thru-Hull with Non-Return Valve Ø25 mm (Lengths 120/150 mm)

This flexible thru-hull with non-return valve is designed to provide automatic drainage (self-bailing) for a boat without the need for a pump, while also preventing water from coming back in through the opening. Its construction is a soft tube/hose that extends outside the hull. When water collects inside the boat (e.g., rain or spray) and the boat is moving, the internal pressure pushes the water out through the flexible tube – the tube opens up and expels water overboard. The moment the internal pressure subsides or a wave hits from outside, the tube automatically pinches closed, acting as a valve to stop backflow. This setup is extremely useful for small open boats that want to shed water while underway.

• Use Cases: Ideal for small powerboats, RIBs, and inflatables (around 3–5 meters) that often accumulate water in the cockpit or bilge. At planing speeds or even moderate forward motion, this flexible valve will evacuate water automatically. It is commonly installed on the transom of inflatable boats as a self-bailer valve
• Two Length Options: The 120 mm version is shorter, suitable for thinner transoms or where a large protrusion isn’t needed. The 150 mm version is longer – useful for thicker hulls or if you want the valve to extend further out (to ensure it reliably pinches closed below the waterline). Both lengths operate identically; the choice depends on your boat’s construction and how far out you want the valve to reach
• Installation: Drill an opening of ~25 mm in the hull (usually low on the transom). Insert the thru-hull from inside so that the flexible part sticks out on the exterior. Tighten the included nut from the inside to clamp the fitting firmly. Ensure the inner flange and gasket sit properly to avoid leaks. The soft tube on the outside remains free – this is the part that acts as the valve
• Material & Durability: The flexible tube is made of a special rubberized plastic that won’t crack from repeated flexing. It’s UV-stabilized and saltwater-resistant, so it can stay exposed to the elements indefinitely. Even in cold weather, the material retains its elasticity to reliably open and close as needed
• Advantages: The key advantage is self-bailing – as you drive the boat, it automatically throws out unwanted water, reducing onboard weight and increasing safety. At the same time, the one-way valve feature protects you when stopped or in waves, preventing the unpleasant situation of water sloshing back in through the drains. With no moving metal parts and no electricity needed, this thru-hull valve is dependable and maintenance-free, aside from occasionally checking that no debris (leaves, seaweed) has lodged in the tube which could hinder its sealing function