Calculating cold water storage tank size requirements

The approach to calculating cold water storage tank capacity depends on the application type:

  • Sizing based on delivery of expected peak flow rate for a duration of 15 minutes; (industry guide, used for most general purpose applications).
  • Recommended minimum storage of cold water based on type of building and occupation (BS EN806-2 Table 6, used for buildings with a specific usage).

Additional Considerations

  • Daily patterns of water use.
  • To maximise water turnover in buildings that have variable occupancy rates, variable height ball/control valves should be used.
  • The CWST should not be oversized as this could result in the stagnation of the stored water.
  • Flow rates for filling cold water storage tanks can vary depending on the amount of storage provided, the pressure available from the source or main and whether the supply is constant - where other information is unavailable, a maximum of four hours filling time may be assumed.