Water Efficiency Calculator for new dwellings Header Image
Home | Calculator | FAQs
Click here for instructions on using the Water Calculator
Installation TypeUnit of MeasureCapacity/Flow rate
Use Factor
Fixed use (litres/person/day)
= [(1)x(2)] + (3)
WC (single flush)Flush Volume (litres)4.420.00
WC (dual flush)Full flush Volume (litres)1.460.00
Part flush Volume (litres)2.960.00
WC (multiple fittings)Average effective
flushing Volume
Taps (excluding kitchen/utility room taps)Flow rate (litres/min)1.581.58
Bath (where shower also present)Capacity to overflow(litres)0.110.00
Shower (where bath also present)Flow Rate(litres / minute)4.370.00
Bath Only Capacity to overflow(litres)0.500.00
Shower Only Flow Rate (litres/minute)5.600.00
Kitchen/Utility room sink taps Flow rate (litres/minute)0.4410.36
Washing Machine (Litres/kg dry load)
Dishwasher (Litres/place setting)
Waste disposal unit (Litres/use)Present 3.080.00
Water Softener (Litres/person/day)1.000.00
(5) Total Calculated use (litres/person/day)
=SUM(column 4)
(6) Contribution from greywater
(7) Contribution from rainwater
(8) Normalisation factor0.91
(9) Total internal water consumption
= [(5)-(6)-(7)]x(8)
(10) External water use5.0
(11) Total water consumption (Building Regulation 17.K)


©Water Research Centre Limited 2024

Terms and Conditions
System Requirements