NSW Plumbing Licence cheat sheet

Minimum sanitary drainage grade is 1:60 (1.7%) for DN100 and smaller, and 1:100 (1%) for DN150 and larger unless the design specifies otherwise.

A water seal trap must hold between 25 mm and 55 mm of seal depth; fixture traps must be self-cleaning and accessible for clearing.

Vent stack sizing follows fixture discharge units: a DN50 vent serves up to 20 fixture units, DN65 up to 60, DN80 up to 140 in typical AS/NZS 3500.2 arrangements.

Every discharge pipe must be tested: water test to 3 m head above the highest point, or air test at 35 kPa for at least 5 minutes with no drop.

Backflow prevention device selection depends on hazard rating: individual (low), zone (medium), or containment (high) protection at the boundary.

Gas pipe sizing uses the longest-run method: total equivalent length (measured length plus allowances for each fitting) sets the pipe diameter from the sizing table.

Gas pressure test: 7 kPa for 10 minutes minimum on natural gas installations, or 1.5 times working pressure for LP Gas, whichever governs.

Combustion air for an indoor gas appliance requires two permanent openings, each sized at 1/1000 of the appliance input in MJ/h for a direct-to-outside duct.

Roof catchment area (m2) equals plan length multiplied by plan width; for pitched roofs use the horizontal plan projection, not the sloping surface.

Rainfall intensity for design is taken from AS/NZS 3500.3 tables by location and storm duration (typically 5-minute and 100-year ARI values).

Box gutter depth must not exceed 1/3 of its width; minimum width 200 mm and minimum depth 75 mm for a standard high-front box gutter with overflow.

Minimum roof slope for corrugated metal sheet is 5 degrees; for lapped metal sheet 3 degrees; for metal tray 1 degree with continuous support.

Downpipe capacity in a charged system is limited by head: a DN90 downpipe carries roughly 380 L/min at 1.5 m head; verify against the manufacturer's chart.

Overflow provisions: an overflow weir or rainhead must be sized to pass the design flow when the primary outlet blocks, at the same design rainfall intensity.

Flashing laps must be 150 mm minimum over the roof covering, 100 mm minimum for side laps, and fixings must not penetrate the flashing within 75 mm of a lap edge.

Sarking and insulation: roof plumber must ensure condensation control layer is continuous and laid with laps facing the direction of water flow.

Medical gas pipeline identification uses colour codes: oxygen white, nitrous oxide blue, medical air black/white, nitrogen black, carbon dioxide grey, vacuum yellow.

A medical gas system must be pressure tested with oil-free dry nitrogen at 1.5 times the design working pressure for a minimum of 24 hours with no pressure loss.

Purity test for medical oxygen: minimum 99.5% oxygen by volume; dew point must be below -46 degrees C for medical air.

Terminal unit flow rates: oxygen and medical air outlets deliver 60-80 L/min at 400 kPa; vacuum outlets deliver 40-80 L/min at 40 kPa below atmospheric.

Mechanical services: air change rates for operating theatres are 20-25 air changes per hour with a positive pressure differential of at least 15 Pa.

Duct pressure testing classifies leakage: Class A (low), Class B (medium), Class C (high); test pressure is 1.25 times design working pressure.

Medical gas alarm systems must be located at the source, at the area alarm panel, and at the master alarm in a continuously staffed location.

Cross-connection test: after any alteration, the pipeline must be purged and tested for identity at each outlet before commissioning.

Only a licensed electrician may perform fixed electrical work; a plumber may disconnect and reconnect fixed electrical equipment only where permitted by the relevant state/territory regulation and within the scope of their licence.

A plumber may disconnect and reconnect a fixed appliance (such as a hot water system or pump) only where the connection is via a plug and socket, or where a restricted electrical licence authorises the work.

Before reconnection, verify polarity and earth continuity; insulation resistance must be at least 1 megohm at 500 V DC test voltage.

Isolation procedure: isolate at the main switch or circuit breaker, lock and tag, prove dead with an approved voltage tester, then proceed.

Circuit protection: a residual current device (RCD) with 30 mA sensitivity protects all socket outlets and lighting circuits in domestic installations.

Cable sizing must account for derating factors: ambient temperature, grouping, and installation method; the protective device rating must not exceed the cable current-carrying capacity.

Earthing: the main earthing conductor minimum size is 6 mm2 copper for a domestic installation with a 100 A consumer mains; verify against AS/NZS 3000 Table 5.1.

After reconnection, test and tag portable appliances; fixed equipment requires a certificate of electrical safety where the work is notifiable.