Pressure transient identification of depleted appliance trap seals: a pressure pulse technique

The appliance trap seal plays a vital role in safeguarding occupied space from ingress of foul sewer gases driven by the barrage of pressure transients generated within the system during normal appliance discharge. The health risks related to depleted trap seals can be severe. In 2003, the rapid spread of the SARS virus at the Amoy Gardens housing complex in Hong Kong was attributed to depleted bathroom floor-drain traps. This paper presents a technique whereby depleted trap seals can be located remotely by monitoring the system response to an applied single pressure pulse. A Method of Characteristic based numerical model allows the system pressure response to be predicted while laboratory and site test results are shown to validate this proposed technique. Practical application: Appliance trap seal depletion poses a serious health risk by providing a route for cross-contamination and infection spread. Implementing a routine and regular maintenance regime would help to ensure that the water level within the trap seal remains above the critical level. However, current methods rely on visual inspections which are highly impractical in large complex buildings. A technique allowing the status of all connected trap seals to be quickly determined would be an invaluable tool for facility managers by improving operational efficiency and by indicating persistent failures, thus, highlighting areas requiring modification to ensure performance compliance. © The Chartered Institution of Building Services Engineers 2008.