The importance of allowing air to enter any soil or waste system should never be overlooked during design and/or installation. The result of poor ventilation is most commonly the siphonic removal of water seals from traps, causing the unpleasant gurgling noise and allowing foul odours to enter living space. FlowPlumb offers the Hunter S450 Air Admittance Valve to ensure adequate ventilation for the drainage system.

Fitted to the top of an internal soil stack, the S450 Air Admittance Valve opens automatically when any appliance is discharged, allowing air into the system. Without it, the vacuum created within the soil system would pull through the water from the traps beneath your basins and floor drains. This would remove the barrier for foul smells from the sail stack to re-enter the room.

Note: outside soil stacks do not need the air admittance valve, but should be topped by a Vent Cowl (S355).

Find out more, and download our Air Admittance valve BBA certificate from our FlowPlumb Downloads page.