An updated water efficiency methodology is now included in Approved Document G. However, there will be cases where the previous document is still relevant (eg for development started before 1 October 2015).
The water calculator Excel spreadsheet has been removed due to technical problems. Free-to-download alternatives are available on the Internet.
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This document sets out the water calculation methodology for assessing the ‘whole-house’ water efficiency of new dwellings.
The calculation method is to be used to assess compliance against the water performance targets in building regulations 17 K. The code for sustainable homes now uses this calculator as the assessment methodology for WAT1.