Pressure transient identification of depleted appliance trap seals: a sinusoidal wave technique

Depleted appliance trap seals were shown to be a causal factor in the spread of the SARS virus at the Amoy Gardens housing complex in Hong Kong in 2003. This serious health risk has emphasised the requirement for an effective maintenance regime to ensure trap seals do not again facilitate the spread of infection and disease. This paper introduces a remote and non-invasive technique to identify depleted trap seals through analysis of the system response to an applied sinusoidal pressure wave. The pressure signal will be analysed in both the time domain and the frequency domain to determine system status. Results obtained from laboratory experiments will be used to confirm the practicality of this technique while a Method of Characteristic based numerical model will validate the methodology. Practical application: The transients generated within the building drainage system as a result of normal system operation continue to pose a threat to the integrity of the appliance trap seal. The technique outlined in this paper will help to quickly identify defective trap seals to ensure that cross-contamination is minimised. However, it is important that this transient-based technique does not itself introduce an additional risk to trap integrity. A sinusoidal pressure wave offers a completely non-invasive testing option that will not only be of great advantage to facility managers but also to the building users due to the reduced risk of cross-contamination. © 2008 SAGE Publications.