A comparison of UK domestic water services sizing methods with each other and with empirical data

Evidence suggests that DCWS sizing methods in many countries around the world tend to overestimate the actual peak water volume flow rate. Oversizing DWS systems does waste materials and money, but it also increases the length of time that it takes for water to pass through the system which can increase water temperatures with the associated risks that presents. This paper compares the three commonly used UK DCWS sizing methods and reveals variance in the methods, the design flow rates calculated and the amount of diversity applied by each method. BS EN 8061 returns the lowest design flow rates of the three methods and also applies significantly greater diversity.

Empirical DCWS volume flow rate data from two case study buildings revealed that all three UK sizing methods significantly overestimated the peak water volume flow rates but that BS EN 8061 was the closest. Additional empirical data from seven more buildings has been used to validate the data from this study and add confidence to the findings. This research provides useful evidence to help engineers select the most appropriate UK DCWS sizing method and to anticipate the likely range and fluctuation of DCWS flow rates.