Potable Water Calculator

A guided 7-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.

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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

7-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 2

Occupants

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

3Step 3

DHW systems

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

4Step 4

Sanitary fixtures

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

5Step 5

Special demands

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

6Step 6

Sustainable supply

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

7Results

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.