The criteria are set to encourage isolation of the water supply to each WC block when it is not being used. If a single flow control device, for example one programmed time controller, is adequate to switch the water on at predetermined times that suit the usage patterns of more than one WC blocks or facilities, this can be used to demonstrate compliance.
Please note that if only one timed controller is used for a large area/number of facilities, the assessor must justify that this is appropriate to the usage patterns within the building and confirm that multiple timers would be redundant (i.e. they would all be set to the same time). Consideration should be given of any facilities that may be open longer than others, requiring these timers to be programmed differently in different areas.
As long as the aim of the credit (‘to reduce the impact of water leaks that may otherwise go undetected’) can be achieved through the specification of an appropriate number of flow control devices, the credit may still be achieved if timers cover more than one WC area/facility to prevent minor water leaks.