Pipe Sizing Calculator Australia — AS/NZS 3500 Compliant

Calculate pipe sizes per AS/NZS 3500 standards — input fixtures, get the correct diameter with clause references and a printable schematic.

How TradeDesk Pipe Sizing Works

TradeDesk's pipe sizing calculator is built directly on the fixture-unit and pipe-size lookup tables from AS/NZS 3500.1 (water supply) and AS/NZS 3500.2 (sanitary drainage). Pick a job template (3-bedroom bathroom group, commercial kitchen, 2-storey residential, etc.) or add fixtures one by one — TradeDesk computes the pipe size for each branch and the main run, applies the correct minimum-pipe-size overrides (e.g. DN100 minimum on the main when 1+ WCs are present), and shows the clause reference for every result.

Each calculation also produces a 2D schematic with the main run, branches, fixtures, and pipe sizes labelled — so you can hand a clean sketch to the apprentice or save it to the job record for your audit trail.

Steps

  1. Pick a template or add fixtures — Quick-start templates for the common scenarios — or add fixtures and quantities one by one.
  2. Choose water supply or sanitary drainage — TradeDesk runs the AS/NZS 3500.1 logic for cold/hot water and AS/NZS 3500.2 for sanitary drainage.
  3. See the result with clause references — Pipe size for each branch and the main run, plus AS/NZS 3500 clause references you can tap to open the standards library.
  4. Save and export — Save the calculation against a job, export the printable schematic, or come back to it from your saved calculations history.

Frequently Asked Questions

Which standards does the calculator use?

TradeDesk's pipe sizing calculator uses fixture-unit and pipe-sizing lookup tables sourced from AS/NZS 3500.1 (water supply) and AS/NZS 3500.2 (sanitary drainage). It applies minimum-pipe-size overrides such as DN80 minimum on the main run for 1 WC and DN100 minimum for 2+ WCs.

Is it accurate enough to size a job?

TradeDesk is a productivity tool — it gives you a fast, clause-referenced first pass. You remain the licensed plumber and you remain responsible for verifying the result against the published Standard, the local water authority's requirements, and any project-specific constraints (head pressure, simultaneous use assumptions, etc.).

Does it handle commercial work?

Yes — there are quick-start templates for commercial bathroom blocks and commercial kitchens, and you can add any combination of fixtures and quantities for bespoke jobs.

Does it cover gas pipe sizing?

Not yet for gas. TradeDesk's gas-side support is currently focused on AS/NZS 5601 standards lookup. Gas pipe sizing (5601 Appendix calculations) is on the roadmap.

How much does it cost?

Pipe sizing is included in the Pro plan, which starts with a 21-day free trial — no credit card required. After the trial, Pro is $79/month or $790/year (save $158).