Marine Plumbing

Marine Plumbing — Onboard Water Systems

Components for the fresh water, raw water and bilge circuits of a vessel: thru-hulls, shut-off valves, branches, elbows and drains. Built to withstand salt corrosion and continuous vibration, in marine bronze, AISI 316 stainless steel, chrome-plated brass and reinforced polymers.

Subcategories: Thru-Hulls · Bronze Ball Valves · Hose Barbs & Adapters · Plugs & Connectors · Bronze T-Fittings · Elbows & Couplings · Drains & Accessories · Water Intakes.

Three plumbing circuits on a boat

Onboard plumbing splits into three independent circuits that should rarely be mixed:

1. Pressurised fresh water: feeds taps, shower, dishwasher and hot water. Pressure pump plus accumulator, in chrome-plated brass or polymer.
2. Raw water / cooling: drawn through Water Intakes, passes through a strainer and supplies the engine heat exchanger, A/C and head. Materials: bronze and AISI 316 stainless.
3. Bilge and drains: removes water from bilge, sink, shower and services through Drains & Accessories and bilge pumps. Gravity or pressurised.

What you will find in this section

• Thru-Hulls — hull penetrations for water intakes and discharges in bronze, stainless, nylon and brass.
• Bronze Ball Valves — quarter-turn shut-off to isolate any branch quickly.
• Hose Barbs & Adapters — flexible hose to rigid pipe or thru-hull connections.
• Plugs & Connectors — to seal unused outlets or to winterise circuits.
• Bronze T-Fittings — three-way branches to add a service without cutting the main line.
• Elbows & Couplings — 90° and 45° direction changes to clear bulkheads and frames.
• Drains & Accessories — deck, shower and sink drains, gratings and outlets.
• Water Intakes — water intakes with integrated thru-hull for engine cooling and A/C.

Materials: when to use each

• Marine bronze (CuSn5Zn5Pb5): the most reliable option below the waterline. Compatible with Marelon valves.
• AISI 316 stainless steel: above the waterline, visible finishes and services without stagnant water.
• Chrome-plated brass: pressurised fresh water, interior plumbing and deck showers.
• Reinforced nylon / Marelon: lightweight and non-conductive, ideal for smaller boats.

Installation best practice

Below the waterline every thru-hull must be combined with a seacock. Use double stainless hose clamps on every barb, PTFE tape on parallel BSP threads and liquid sealant on tapered ones. Check torque and watertightness each season.

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