Forespar Marelon 5/8″ Vented Loop/Siphon Valve

Vented loops are vital components to any onboard plumbing system, helping reduce the risk of sinking or flooding. The glass reinforced composite Marelon Vented Loops allow air to enter the lines, preventing dangerous back siphoning when pumps are turned off.

Key Features

• Marelon vented loop design helps stop back siphoning by allowing air to enter the line.
• Glass reinforced composite construction for corrosion resistance in marine plumbing applications.
• Recommended for installation above the waterline on head discharge, bilge pump, engine, gen-set, air conditioner, ballast tank, and other onboard equipment systems.

Product Compatibility

• Head discharge systems (marine sanitation)
• Bilge pump plumbing
• Engine and generator set related discharge/plumbing lines
• Air conditioner related discharge/plumbing lines
• Ballast tank plumbing
• Other onboard equipment plumbing lines (as indicated by your system design)

Product Details

• Marelon Vented Loop with integrated siphon/anti-siphon venting function (part number 108-903003).
• Size: 5/8″ vented loop.
• Molded in glass-reinforced composite Marelon (per Marelon plumbing vented loop product materials).
• Vented loop placement: install above the waterline (recommended installation guidance used for Marelon vented loops).
• Contents/kit details: not specified in provided product data; install using the appropriate plumbing hose/connector method for your system.

Parts Desk Insights

Best Use Case: Use this 5/8″ Marelon vented loop on marine plumbing runs where back siphoning and unwanted water transfer after pump shutoff are concernsespecially for discharge lines that should remain protected from flooding effects when equipment turns off.

Common Issues: If venting isnt performing as expected, the usual causes are poor placement (not sufficiently above the waterline), restrictions or improper hose routing, or mating/connection issues at the loop inlet/outlet. Confirm hose routing and any associated fittings/gaskets align with your plumbing layout and the Marelon vented-loop installation guidance.

Related Products & Accessories

• Vented Loops / Replacement Vent Caps (browse category) – Choose the correct vented-loop size and configuration (e.g., cap/vent-barb variations) to match your hose and installation style.