First-fix plumbing

First-fix plumbing is the plumbing rough-in stage on a residential build: the underground sewer drain, stormwater pipework, sanitary stack, and hot- and cold-water service runs are installed to each fixture location before the slab is poured or the wall and floor framing is closed up. It precedes second-fix plumbing (fitoff), where the visible fittings (taps, basins, toilets, dishwasher connections) are connected to the rough-in stub-outs.

The scope of first-fix plumbing typically covers under-slab drainage (sewer, floor wastes, stormwater, pressure-tested before backfill), the sanitary stack running from upper-floor fixtures down to the sewer main, hot- and cold-water rough-in terminated at stub-outs at the correct height and offset for each fixture, and (where applicable) gas pipework to appliance locations. Gas work falls under AS/NZS 5601 and the gasfitter’s separate Certificate of Compliance, not the plumbing CoC.

First-fix plumbing is governed by AS/NZS 3500, the plumbing and drainage standard, and is the plumber’s scope. It is notifiable work in most states: the plumbing regulator must be notified before concealment so the inspector can verify pipe sizing, gradient, support, and pressure-test results. Concealing first-fix plumbing without notification is a common compliance breach.

Two failure modes show up most often: wrong stub-out heights or offsets (the tiler or chippy cannot fit the fixture; pipework must be cut into the wall after lining, damaging waterproofing and tile), and insufficient drainage fall on under-slab sewer or stormwater (ponding or backflow in service).

The plumbing Certificate of Compliance is issued at second-fix completion, but the first-fix inspection is the gating check before the slab pours or the linings go on.

Also known as: plumbing rough-in, hydraulic rough-in.

Category: Build sequence / plumbing / notifiable work.

Related

See also

Related articles