Forespar Marelon 3/4″ Vented Loop/Siphon Valve

Vented loops help protect onboard plumbing systems by breaking siphon effects when pumps are turned off. This Forespar Marelon 3/4″ Vented Loop/Siphon Valve uses a one-way vent cap to allow air to enter the line while sealing when fluid is present, helping reduce the risk of backflow and flooding.

Key Features

• Designed for marine plumbing to help reduce dangerous back siphoning when the connected pump/system is off.
• Marelon construction: glass reinforced composite (helps resist corrosion for both the vent and loop).
• Air-entry vent cap with a one-way duck-bill style valve inside helps the loop vent the line when needed.
• Use in systems where you want anti-siphon protection above the waterline (e.g., sanitation/discharge and bilge-related plumbing).

Product Compatibility

• Marine plumbing systems requiring anti-siphon protection on discharge or outlet hoses
• Sanitation/head discharge plumbing
• Bilge pump outlet and related plumbing (where vented-loop installation above the waterline is appropriate)
• Engine/gen-set or other onboard equipment plumbing/discharge lines

Product Details

• Item: Forespar Marelon 3/4″ Vented Loop/Siphon Valve
• SKU: 108-903001
• Barb/hose size: 3/4″
• Overall size: 4-1/2″ H x 3-3/4″ W
• UPC/GTIN (as provided in product data): 28026148728
• Product type: vented loop / siphon valve assembly
• Weight (as provided in product data): 113 grams

Parts Desk Insights

Best Use Case: Install as part of an anti-siphon setup on discharge/outlet plumbing where the vented loop is located above the waterline.

Common Issues: If siphoning still occurs, confirm the vented loop is positioned correctly above the waterline and that hose connections are secure and unobstructed; also ensure the vent-cap/one-way valve is functioning as intended and that particulate matter isnt preventing proper sealing.

Related Products & Accessories

Browse related Bilge Pumps to complete the installation.