Whenever syphonic conditions develop, the negative pressure causes the Valve to rise, allowing air to be drawn into the discharge pipe. The pressure is thereby neutralised before it can have any effect on the water seal within the Trap. On cessation of the syphonic action, the Valve closes, making the Silentrap air and watertight Advantages For remote delivery locations and offshore islands these may take longer to arrive, and in certain circumstances further delivery charges may apply. These locations include / but are not restricted to UK Highlands and Islands, UK Non Mainland, Isle of Wight and Northern Ireland. The Silentrap has been most rigorously tested and will not unseal, even under the most abnormal conditions The major advantage of the Silentrap over Resealing Traps is that because the air is drawn through the Valve and not through the water seal, gurgling is eliminated and a much quieter discharge is ensured By drawing air through the Valve, the Silentrap neutralises syphonic pressure before it reaches the seal of the Trap and therefore provides the equivalent of a ventilated system without the installation of costly and unsightly ventilation pipes

The Silentrap should continue to be effective irrespective of the distance between the appliance and the soil pipe