Water Calculator

A guided 8-step workflow to model actual vs notional potable water demand, optimise sustainable supply and earn Green Star D-4 credit points — built directly from the GBCSA Green Star SA v2 Rev 5 specification.

D-4 Water Credit

Covers the full Green Star SA v2 Potable Water Calculator — actual vs notional demand, reduction percentage and credit points.

All fixture types

WC, urinals (manual & auto-timer), indoor taps, showers and baths — each with actual flow rates and occupancy linking.

Sustainable supply

Greywater, rainwater and off-site supply all modelled and offset against potable demand automatically.

Instant scoring

Actual vs notional consumption computed in real time; Green Star points displayed as soon as inputs are complete.

How it works

8-step workflow

Walk through the Potable Water Calculator section by section — from building inputs to final scoring.

1Step 1

Project information

Name, team contacts, SANS climate zone and city location.

2Step 1

Area schedule

SANS primary space types, gross floor areas, holiday periods.

3Step 1b

DHW systems

List each domestic hot water system: heating source and storage volume.

4Step 1a

Occupants

Occupant groups, design numbers, profiles, shower/bath usage and urinals.

5Step 2a

Sanitary fixtures

WC flush rates, urinals, indoor taps, showers and baths per fitting type.

6Steps 2b–2g

Special demands

Cooling towers, irrigation, pools, laundry, kitchens and other major uses.

7Step 3

Sustainable supply

Greywater reuse, rainwater harvesting and off-site sustainable supply.

8Results

Review & results

Confirm all inputs, view actual vs notional demand and Green Star score.

Ready to calculate?

Create a new project, enter your building data and walk through the workflow to model your water usage and earn Green Star credits.