Drainer | Chalkline

A drainer is the plumbing sub-trade licensed for sanitary and stormwater drainage below ground. In most Australian states, drainage work requires a separate licence from general plumbing: a plumber qualified to install bathrooms and kitchens may not be authorised to connect to the mains sewer or to build stormwater drainage systems. The two licences sometimes overlap on one tradesperson but the work category and inspection regime are distinct.

What a drainer does on a residential build:

Mains sewer connections: from the building to the council sewer or septic system, including the inspection opening and the boundary trap (where required).
Storm-water drainage: roof downpipes to the kerb adapter, pit, soak well, or absorption trench. Includes ag drain in retaining-wall context.
Below-slab DWV (drainage, waste, vent): every pipe that runs through the slab for waste from internal fixtures. Set out and roughed-in before slab pour.
Boundary trap, inspection opening: the council-mandated inspection point at the property boundary.
Soak wells and absorption trenches: stormwater dispersal where direct connection to council is unavailable.
Trench backfill specification: drainer typically supervises or sets the backfill spec around their pipework.

What a plumber does (and a drainer may not):

Above-ground pipework: hot, cold, and waste pipework within the building.
Fixture installation: taps, toilets, basins, hot water units.
Gas pipework (gasfitter licence required separately).

State licence distinctions (typical, varies by state):

NSW: Plumber, Drainer, Gasfitter are separate certificates of competence under NSW Fair Trading.
VIC: Plumber registration with categories. Drainage Plumbing is a specific licence class under the VBA.
QLD: Plumber and Drainer licences under QBCC. Drainage is a sub-licence class.
WA, SA, TAS, ACT, NT: similar distinct or sub-class arrangements.

Drainer’s role in the build sequence:

Pre-slab: set out below-slab DWV, sleeves through slab edge beams for service entries, council inspection point.
Council connection: connect from building rough-in to mains sewer; council inspection at this stage.
Stormwater: install downpipe connections, kerb adapter, pits, soak wells. Often after roof is on.
Final inspection: drainer’s Certificate of Compliance for the drainage work, lodged with council and on the build pack.

Common builder issues:

Plumber and drainer confused at quote stage: assuming one person does both. Often two trades, two licences, two sets of certificates.
Drainer not engaged early enough: pre-slab pipework set out late, causing slab redesign. Drainer should be on the project at slab-design stage.
Stormwater design not coordinated with drainage: roof catchment vs soak well capacity not matched; flooding in heavy rain.
Council inspection missed: mains connection inspection bypassed; council insists on opening up the connection for re-inspection.

For builders:

Engage a licensed drainer specifically for below-ground work. Confirm the licence class matches the work.
Coordinate with the plumber on rough-in heights; drainer’s pipework sets the levels the plumber’s fittings will land on.
Get the drainer’s Certificate of Compliance at completion; the build pack needs it for OC.

Also known as: licensed drainer, drainage plumber, sanitary drainer.

Category: Trades / plumbing / licensing.

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