Vented loops

A vented loop, also known as an anti-siphon valve, is a marine plumbing safety device designed to prevent siphoning. It allows air to enter a hose when pressure drops, breaking the water column and stopping unwanted backflow into the boat. Vented loops help prevent flooding and water damage by stopping seawater from flowing back into onboard systems. They are a critical safety component in installations where hoses run below the waterline.