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. Hunter offer the S450 Air Admittance Valve to ensure adequate ventilation for the drainage system. For waste applications, Multikwik have products for domestic and commercial installations.