Downtime of in-use water pump installations for high-rise residential buildings

This study examines the fresh and flushing water pump installations for high-rise residential buildings in Hong Kong in terms of system availability, mean time to failure, mean time between failures and restoration time. Together with some reliability data published elsewhere, it applies Bayesian analysis to improve our understanding of the downtime characteristics of water pump installations. For three consecutive years (2005-2007), water pump failures in 46 typical high-rise residential buildings were recorded to determine the component failure rates. In order to study the failure patterns, Monte Carlo simulations were performed for the operations of 100 parallel pump sets over a period of 10 years. The mean time to failure, total downtime, failure counts and system availability estimated for the fresh water pump installations were 1.24 years, 8990 h, 709 and 90% while those estimated for the flushing seawater pump installations were 0.46 years, 4049 h, 2081 and 78%, respectively. The results are useful in the calculation of water supply availability for high-rise residential buildings while keeping the balance between maintenance cost and system reliability. This study also demonstrates a method for reliability modelling of water supply for high-rise residential buildings.Practical applications: This study demonstrates a method for reliability modelling of building services systems. With the use of Bayesian analysis, example estimates of the mean time to failure, total downtime, failure counts and system availability were determined for the fresh and flushing water pump installations for high-rise residential buildings in Hong Kong.