PGDB Certifying Plumber cheat sheet

Gradient for DN100 sewer: 1:60 (1.67%) minimum; DN150: 1:100 (1.0%) minimum; use 1:40 to 1:60 for small bore.

Vent stack must extend at least 150 mm above roof and not less than 3 m from any openable window; terminal area 0.05 m².

Trap seal depth: 25–50 mm for fixtures; 50 mm minimum for floor waste; 75 mm for gully traps. Seal loss occurs if venting is inadequate.

Fixture unit method: 1 FU = 0.03 L/s; discharge from 10 WC (10×6 FU=60 FU) requires DN100 pipe at 1:60 carrying ~2.0 L/s.

Junction angles: 45° or 88.5° for horizontal to vertical; 45° Y branches for vertical to horizontal; no 90° elbows in drainage.

Inspection openings required at base of each stack, at changes of direction >45°, and at intervals ≤15 m on horizontal drains.

Backdrop or cascade: use when fall exceeds 1:1; provide 45° slope and vent at top; maximum 6 m vertical drop per stage.

Pumped discharge: sump capacity ≥ 3 minutes inflow; discharge pipe sized for velocity ≥0.9 m/s; non-return valve and alarm required.

Minimum pressure at fixture: 50 kPa for taps, 100 kPa for showers, 150 kPa for flush valves; maximum static pressure 500 kPa.

Flow rate for DN20 copper at 0.5 m/s ≈ 0.25 L/s; use velocity limit 1.5 m/s for cold, 1.0 m/s for hot to control noise and erosion.

Backflow hazard: high hazard requires reduced pressure zone (RPZ) device; medium hazard requires double check valve; low hazard requires single check.

Test RPZ annually: check valve tightness, relief valve opening at 14–21 kPa differential, and air inlet opens fully.

Water hammer arrestor sized per fixture units; install near quick-closing valves; pressure surge must not exceed 1.5× working pressure.

Thermostatic mixing valve: outlet 45 °C max for domestic; 50 °C for aged care; tempering valve required on storage water heaters.

Pipe sizing: use Darcy-Weisbach or AS/NZS 3500.1 tables; account for friction loss in fittings (equivalent length method).

Cross-connection control: physical air gap of 2× pipe diameter (min 25 mm) is the only acceptable high-hazard protection for potable supply.

Gas pipe sizing: use table based on allowable pressure drop (0.75 kPa for natural gas, 2.75 kPa for LPG) and gas rate in MJ/h.

Clearance from gas appliance to combustible surface: 200 mm for flue, 50 mm for appliance body; follow manufacturer's instructions if greater.

Ventilation for gas appliance: open flue requires permanent ventilation openings 2× cross-section of flue; room volume ≥ 4 m³ per kW.

Pressure test: natural gas 7 kPa for 10 min, no drop; LPG 7 kPa for 10 min; test with air or inert gas, never with gas.

Gas leak detection: use soap solution or electronic detector; never flame. Leak rate >0.5 L/h requires isolation and repair.

Regulator: set outlet pressure to 1.0–1.5 kPa for natural gas appliances; 2.75 kPa for LPG; lock-up pressure ≤1.25× set pressure.

Flue terminal clearances: 500 mm from openable window, 300 mm from non-openable, 1000 mm from boundary, 1500 mm from mechanical air intake.

Combustion air: 1 m² free area per 250 MJ/h for natural gas; 1 m² per 125 MJ/h for LPG; use louvre free area 50%.

Roof slope: metal sheet ≥5° (1:12); tiles ≥15° (1:4); low-pitch membrane ≥1.5° (1:40). Increase for snow/wind zones.

Rainfall intensity: use 1% AEP (1 in 100 year) for design; 5-minute duration for small roofs (<200 m²), 20-minute for larger.

Box gutter sizing: use Manning's n=0.015; minimum width 300 mm; depth ≥150 mm; overflow provision required (e.g., sump or side outlet).

Downpipe capacity: DN100 round = 0.20 L/s per m² roof at 100 mm/h; DN150 = 0.45 L/s; rectangular 100×50 = 0.15 L/s.

Stormwater pipe gradient: 1:100 minimum; 1:50 for flat grades; velocity ≥0.6 m/s self-cleansing; max 3 m/s to prevent scour.

Overflow relief: provide 1.5× design flow capacity; weir or overflow pipe sized for 1% AEP plus blockage scenario.

Roof drainage: gutters must have fall ≥1:500; expansion joints every 12 m; leaf guards required on all outlets.

Detention/retention: onsite detention volume = (post-development runoff - pre-development runoff) × duration; use 1% AEP critical duration.

Drawing scale: 1:100 for floor plans, 1:50 for details, 1:20 for assemblies; always note scale and units (mm).

Line types: solid thick = below-ground drainage; solid thin = above-ground; dashed = concealed; dash-dot = centreline.

Symbols: circle with cross = floor waste; triangle = vent; square with diagonal = inspection opening; arrows indicate flow direction.

Specification must reference AS/NZS 3500 series, AS 5601 for gas, AS 2200 for drawings, and NCC volume.

Pipe sizing calculations must be submitted for water supply, drainage, gas, and stormwater; include fixture unit count and pressure drop.

As-built drawings: update all changes, show invert levels, coordinates, and material types; deliver within 10 business days of completion.

Coordination: check clash detection between services (plumbing vs. electrical vs. structural); maintain 100 mm clearance between hot and cold pipes.

Legend required on every drawing: list all abbreviations, symbols, and pipe materials (e.g., uPVC, copper, PEX).

National Construction Code (NCC) Volume Three contains Plumbing Code of Australia (PCA); compliance is mandatory for all plumbing work.

AS/NZS 3500.0–4 covers plumbing and drainage; AS 5601 gas installations; AS 2845 backflow prevention; AS 2200 drawing practice.

Notifiable work: must be inspected by plumbing regulator before concealment; provide notice at least 48 hours before covering.

Certificate of Compliance (CoC) issued for all regulated work; retain copy for 7 years; include test results and defects.

Penalties for unlicensed work: fines up to $50,000 for individuals, $250,000 for corporations; imprisonment for repeat offences.

Continuing professional development (CPD): 12 hours per year for licensed plumbers; include 4 hours on regulatory updates.

Work health and safety (WHS) obligations: PCBU must manage risks; plumbers must follow safe work method statements (SWMS) for high-risk work.

Environmental compliance: trade waste permit required for discharge to sewer; pH 6–10, no prohibited substances; grease trap for food premises.

Personal protective equipment (PPE): safety glasses, gloves, boots, hard hat, high-vis vest, hearing protection when >85 dB(A).

Confined space entry: test atmosphere for oxygen (19.5–23.5%), LEL <5%, H2S <10 ppm, CO <30 ppm before entry; use gas detector.

Hazardous substances: SDS must be available for all chemicals; store fuels and solvents in bunded areas with 110% capacity.

Manual handling: max 20 kg per person; use trolleys or team lift for heavier; assess risk using WHS regulations.

Excavation: shoring required for trenches >1.5 m deep; ladder every 9 m; spoil away from edge by 0.5 m.

Environmental: prevent sediment runoff using silt fences; manage waste segregation (copper, PVC, general); no discharge to stormwater.

First aid: kit on site; trained first aider for >10 workers; emergency plan displayed; contact numbers for poisons information.

Electrical safety: use RCD (30 mA) for all portable tools; inspect leads before use; no water near electrical equipment.

Contract types: fixed price, schedule of rates, cost plus; fixed price shifts risk to contractor; include variation clause.

Progress payments: claim at milestones; under security of payment legislation, payment due within 15 business days of claim.

Retention: typically 5% of contract value held for 12 months; reduce to 2.5% at practical completion.

Variations: must be in writing, signed by both parties before work; price using contract rates or reasonable rates.

Insurance: public liability ≥ $10 million; contract works insurance; workers compensation mandatory.

Quotation: include scope, exclusions, assumptions, validity period (30 days), and terms of payment.

Consumer guarantees: work must be done with due care and skill, fit for purpose, and completed within reasonable time under Australian Consumer Law.

Dispute resolution: follow contract dispute clause; mediation before litigation; keep records of all communications.

Supervision ratio: 1 licensed plumber to 2 apprentices for on-site work; direct supervision required for notifiable work.

Quality assurance: inspection and test plan (ITP) for each stage; hold points require sign-off before proceeding.

Competency assessment: use units of competency from CPC training package; verify skills through practical demonstration and written test.

Mentoring: set clear goals, provide feedback, use structured on-the-job training; document progress in training record book.

Toolbox talks: conduct weekly; record attendance and topics; include safety, quality, and environmental issues.

Non-conformance: document, isolate, rectify, and verify; root cause analysis to prevent recurrence.

Handover: provide as-built drawings, operation manuals, maintenance schedules, and compliance certificates to client.

Audit: internal audits every 6 months; check calibration of test equipment, record keeping, and adherence to procedures.