The Lippert 389381 360 Siphon roof vent cap is an aerodynamically engineered plumbing vent that captures wind from every direction and uses it to create a continuous low-pressure zone above your sanitation stack -- pulling holding tank fumes out rather than letting them linger or push back down. Whether your RV is parked or rolling, even a slight breeze activates the siphon effect. No moving parts, no maintenance, and a built-in bug screen keep it working season after season.
Most stock RV plumbing vent caps do nothing more than keep rain out. The Lippert 360 Siphon is purpose-engineered to actively draw fumes up and out. Its 360-degree aerodynamic housing captures airflow from any compass direction and channels it inward, accelerating air toward the center of the cap and creating a venturi-style low-pressure zone directly above the pipe opening.
Because the design physically prevents high-pressure air from entering the stack, downdrafts -- one of the leading causes of sewer smell inside the RV -- are eliminated. The increased airflow through the tank also speeds up the aerobic breakdown of waste, reducing odor buildup over time.
Aerodynamic housing channels wind from any direction into a low-pressure zone above the stack, pulling fumes out continuously.
Universal fit over both common RV sanitation stack diameters. No adapter needed for most installations.
Integrated screen keeps insects from nesting in the vent pipe -- a common problem in storage season with standard open caps.
Strong, UV-resistant polycarbonate resists cracking, fading, and warping through years of rooftop sun and temperature cycling.
Conventional vent caps are passive -- they rely on thermal convection or significant wind to move air through the stack. The 360 Siphon uses a venturi-inspired geometry: the outer ring captures and accelerates ambient wind regardless of direction, then redirects it across the central opening. This drop in localized air pressure actively draws air upward through the pipe, mimicking the effect of a constantly running exhaust fan with zero electricity required.
The design also makes it structurally impossible for wind to reverse-flow into the stack. Side pressure from gusts is redirected around the cap rather than funneled down, so you won't get the characteristic "sewer smell in the bathroom" that results from a downdraft pushing tank gases through the P-trap.
The 360 Siphon replaces your existing plumbing vent cap directly. Remove the old cap, set the siphon over the pipe stack, and secure with the original mounting screws (the screw pattern is compatible with most factory vent caps). Seal around the base with a lap sealant.
Holding tanks that vent freely have better aerobic conditions, which supports the activity of tank treatment bacteria and enzymes. More consistent airflow through the stack means treatment products like enzyme-based tank treatments work more effectively, and solid waste breaks down faster -- reducing the frequency of hard-to-flush deposits and the buildup of hydrogen sulfide (the primary odor compound in sewer gas).