Marine Vented Loop, VL-15, 1-1/2"Scot Pump Marine Vented Loops: Unparalleled Solutions for Yachts, Workboats, and the Fishing Industry Installing our vented loop prevents fluid from siphoning between tanks, ensuring reliable operation. Commonly used in marine toilet and engine cooling systems, it provides essential protection against unwanted backflow. Overview Sensitive Breaker automatically opens and prevents back siphoning. Normally closed two feet of water vacuum will cause