Marine toilet vented loop 81-47237 series

The vented loop is available in different sizes and with its inverted U-shape with a vent at the top it allows the air to escape. Vented loops are to prevent back siphoning and are found in toilet discharge lines or in systems which are mounted below the waterline. Vented Loop, ¾" (19mm) Vented Loop, 1" (25mm) Vented Loop, 1½" (38mm)