Through-hull fittings
Through-hull fittings are essential components of any boat plumbing system, allowing water to safely enter or exit the hull. They are commonly used for seawater intakes, drains, cooling systems, toilets, bilge pumps and sinks. Choosing the right through-hull fitting is critical for safety, durability and long-term reliability on board.
Our range of marine through-hull fittings includes high-quality solutions from Guidi and Trudesign. Available in different materials and a wide range of sizes to match standard hose diameters, our through-hull fittings are designed for use in saltwater and freshwater environments. All fittings meet marine safety standards and are compatible with ball valves and hose fittings for complete plumbing installations.
Thru-hull standard shape brass threadedAs low as €7.62
Thru-hull chrome plated brass, threadedAs low as €13.67
Thru-Hull flush head brass threadedAs low as €9.40
Trudesign load bearing collarAs low as €21.30
Trudesign skin fitting domedAs low as €9.50
Trudesign skin fitting flushAs low as €9.50
Trudesign skin fitting long thread BSPAs low as €16.90
Trudesign skin fitting hose with tailAs low as €9.90
Water inlet 3/4"Special Price €30.78 Regular Price €32.40
What are through-hull fittings used for?
Through-hull fittings are used anywhere water needs to enter or leave the boat, for example:
- Seawater intake for engine cooling systems
- Toilet inlet and outlet systems
- Sink and shower drains
- Bilge pump discharge
- Grey water discharge (where applicable)
How do through-hull fittings work in a plumbing system?
A through-hull fitting provides the hull penetration point. On the inside of the hull it is typically connected to:
- A ball valve / seacock (for shut-off and safety)
- A hose connection (via a hose fitting)
- Sometimes a strainer (on intakes)
- This creates a controlled and secure path for water flow.
What materials are available and how do I choose?
Common marine materials include:
- Brass: strong, long-lasting and widely used below the waterline
- Stainless steel: high strength and clean appearance; correct grade is important for marine corrosion resistance
- Plastic: lightweight, corrosion-free and electrically insulating (helps avoid galvanic corrosion)
Choose based on your environment (salt/freshwater), compatibility with other components, and your boat’s installation requirements.
What sizes are through-hull fittings available in?
Through-hull fittings are available in multiple diameters to match standard hose sizes and plumbing connections. Typical sizing is based on:
- Hose diameter (e.g., common marine hose sizes)
- Thread size (for connecting valves or fittings)
Always measure your existing installation or plan your full system (valve + hose + clamp) before selecting a size.
Where should through-hull fittings be installed?
Through-hull fittings can be installed above or below the waterline, depending on the system. Below-waterline installations require extra care and are normally paired with a shut-off valve for safety.