Learn more about Boat thru-hulls

Thru-hulls are essential for ensuring safe hull penetration in water, fuel, or drainage systems. At DAM Marine, we offer a full range tailored to every need:

• Stainless steel thru-hulls: highly corrosion resistant
• Delrin thru-hulls: lightweight, economical and durable
• Bronze thru-hulls: robust, ideal for submerged zones
• Nylon thru-hulls: easy to install, perfect for dry areas
• Strainer thru-hulls in brass, bronze or stainless steel: with integrated filtering

Compliant with marine requirements, our thru-hulls ensure watertightness, reliability and resistance in all conditions.

Choose DAM Marine for your hull equipment, with a complete selection and professional advice.

Boat through-hull fittings

The through-hull fitting is an essential product for the safety and maintenance of your boat, whether it's a sailboat, yacht, motorboat, RIB or catamaran. This threaded or barbed fitting, made of brass, bronze, stainless steel, or plastic (nylon, PVC, Trudesign, white, Delrin), ensures a watertight connection between the inside and outside of the hull for drainage, water intake, engine return, or bilge discharge. Each product is carefully listed in our marine catalog. DAM Marine stocks and ships a large range of fittings, accessories, and variants at competitive prices for all types of hulls and nautical installations, meeting the needs of boaters.

What is a through-hull fitting and what is its purpose?

A through-hull fitting is an indispensable marine item, made up of a threaded or barbed tube, usually in brass, bronze, stainless steel, plastic (nylon, PVC, Trudesign, white, Delrin), or stainless steel. The body may be cylindrical to match certain connection types. This product allows for a watertight passage through the boat's hull to connect a hose, valve, strainer, or fitting. It enables engine water intake, cockpit drainage, bilge emptying, installation of sensors or nautical accessories. Depending on the category and diameter, it can be installed above or below the waterline, ensuring your vessel’s safety and upkeep on every trip — an essential component for any skipper.

The crucial choice of material for your through-hull fitting

Choosing the material for your through-hull fitting is crucial for the safety and longevity of your boat, whether it's a sailboat, yacht, motorboat or catamaran. DAM Marine offers through-hulls made of plastic (nylon, PVC, Trudesign, white, Delrin), brass, bronze, stainless steel or inox, suitable for every type of hull and setup. Plastic, light and economical, is suitable for outlets above the waterline. Bronze and stainless steel are recommended for below-waterline installations due to their excellent resistance to marine corrosion and durability, ideal for recreational boating and heavy use. Brass, sometimes chrome-plated, offers a sleek finish and good resistance, but must be chosen carefully depending on the marine environment. Stainless steel through-hulls are less common but appreciated for their robustness. Each material has its pros and cons in terms of price, maintenance, installation and compatibility with accessories (valves, strainers, fittings, connectors) on all types of boats. DAM Marine provides all variants to meet every need, from engine connections to bilge discharge.

Discover all our through-hulls available on our website:

• Brass through-hulls
• Stainless steel through-hulls
• Delrin through-hulls
• Bronze through-hulls
• Nylon through-hulls
• Brass strainer through-hulls
• Bronze strainer through-hulls
• Stainless steel strainer through-hulls

Types and technical features of through-hull fittings

Through-hull fittings come in multiple variants to adapt to every boat, sailboat, yacht or motorboat installation. Some may be installed on the bow for specific water intake or discharge purposes. There are threaded outlets, ideal for connecting accessories or valves, and barbed outlets, perfect for attaching flexible hoses using a hose clamp. DAM Marine offers a wide range of diameters (e.g. 3/4 inch, 24 mm, 50 mm) to meet all needs — discharge, intake, or engine return. Some models are fitted with a check valve or angled design to ease installation in the bilge or cockpit. Exhaust through-hulls are designed with thermal isolation to protect the hull and ensure safety and maintenance during each outing.

Safe installation and required maintenance of a through-hull fitting

Installing a through-hull fitting is a crucial step for the safety of your boat, whether it’s a sailboat, yacht, motorboat or RIB. It's essential to carefully prepare the hull opening, respecting the product diameter and its installation category (above or below the waterline). Apply a marine sealant suitable for permanent immersion to ensure watertightness. For double-skin hulls, reinforcing the perimeter with resin is recommended. The through-hull fitting, whether threaded or barbed, must be tightened gradually, and then connected to a hose with robust clamps — ideally two below the waterline to meet nautical standards. Threaded models are particularly suitable for setups requiring regular disassembly. Flexible hoses must be checked regularly to prevent leaks. Installing a compatible valve, strainer, or fitting completes the system for reliable discharge or intake. Regular maintenance is essential: check the condition of through-hulls, valves, strainers and accessories to prevent corrosion or leaks. Some models allow sensors to be removed while afloat, making maintenance easier without hauling out the boat. DAM Marine offers all the necessary items for a safe installation, so you can sail with peace of mind and extend the life of your fittings.

Additional elements: valves, strainers and fittings

To ensure a secure onboard water circuit, through-hulls are often paired with valves (ball or bearing) that allow for quick shut-off in case of emergency or maintenance. Strainers made of bronze, stainless steel, brass or plastic filter seawater at entry, protecting the engine, bilge pump or sanitary systems. They are also recommended for seawater circuits used during anchoring. Depending on the need, strainers may be screw-mounted on the hull or integrated into the through-hull fitting, and are available in various diameters and designs. To complete the installation, DAM Marine also offers all the connectors, hose clamps, deck fillers, hoses, end fittings, compasses and accessories needed for reliable water intake or discharge during every outing. Proper connection of these components is essential for ensuring boat safety.

DAM Marine.com: your expert in through-hull fittings and related equipment

Choose quality products tailored to each type of boat: sailboat, yacht, motorboat or RIB. DAM Marine is a trusted supplier of marine parts. Explore our catalog, use the available filters to find the right through-hull fitting, and benefit from renowned brands. Take advantage of fast shipping, customer reviews and expert nautical advice to find the ideal solution and sail with confidence. Full technical details are available on each product page to help you make the right choice.