Cert III Plumbing cheat sheet

Hierarchy of control, highest to lowest: eliminate the hazard, substitute, isolate, engineer controls, administrative controls, then PPE as the last line of defence.

Duty holders under WHS law include the PCBU (primary duty of care), officers (due diligence), workers (take reasonable care, follow instructions, report hazards) and other persons at the workplace.

SWMS (safe work method statement) is mandatory for high-risk construction work such as work at height above 2 m, trenching deeper than 1.5 m, and work near energised electrical installations.

Incident notification: a death, serious injury or illness, or dangerous incident must be reported to the regulator immediately by phone, with written notice within 48 hours.

Hazardous manual tasks are managed by the risk assessment order: identify the task, assess risk factors (posture, force, repetition, duration), then control and review.

Confined space entry requires an entry permit, atmospheric testing (oxygen 19.5-23.5%, LEL below 5%, H2S and CO within limits), a standby person, and rescue arrangements before entry.

Asbestos: any building constructed or renovated before 1990 may contain asbestos; a licensed removalist is required for friable asbestos and for non-friable asbestos above 10 square metres.

Electrical safety on site: test-and-tag applies to portable equipment, RCDs (30 mA) protect final subcircuits, and no work within the exclusion zone near overhead lines without the supply authority isolating.

Waste hierarchy order: avoid, reduce, reuse, recycle, recover energy, then dispose; silt and sediment must be trapped before stormwater discharge.

Sediment control devices include silt fences, sediment basins, catch drains and hay bales; they are inspected after rain and maintained until site stabilisation.

Trade waste from plumbing (solder dross, solvent cement, waste oil, lead, flux residues) is classified and disposed of through licensed contractors, never to stormwater.

Water efficiency ratings: WELS star ratings label fixtures; 6-star or equivalent toilets, tapware and shower heads reduce demand; rainwater tanks supply non-potable uses such as toilet flushing and irrigation.

Backflow prevention protects potable supply: testable devices (RPZD, double check) require annual testing by an accredited tester and records kept on site.

Quality documentation includes ITPs (inspection and test plans), hold points, material certificates, and compliance certificates issued for plumbing work under state plumbing regulations.

Concrete washout must occur in a bunded washout area, not on site drainage; wash water is pH-tested and neutralised before disposal.

Noise, dust and vibration controls are conditions of consent; work hours are limited by local council approvals and must be recorded in the site environmental management plan.

Pipe volume: V = pi x r^2 x L; for a 100 mm diameter pipe, r = 0.05 m, so volume per metre = 3.1416 x 0.0025 x 1 = 0.00785 m3, i.e. 7.85 litres per metre.

Fall calculation: fall (mm) = gradient (1 in X) x length (mm) / X, or fall = length x grade; a 1 in 60 fall over 12 m = 12000/60 = 200 mm.

Copper tube sizing: nominal size refers to outside diameter for metric copper; Type A, B, C and D differ in wall thickness, with A being thinnest and D thickest.

PVC pressure pipe is classified by PN rating (PN9, PN12, PN15, PN18); sewer and stormwater PVC is SN-rated for stiffness (SN4, SN8, SN10).

Thread standards: BSP is the Australian pipe thread; a 15 mm (1/2 inch) BSP thread has approximately 14 threads per inch, and thread sealant or PTFE tape is applied to male threads.

Torque and pressure: pressure (kPa) = force (N) / area (m2); 1 bar = 100 kPa = 10 m head of water approximately.

Material selection: DWV PVC for drainage and vent, copper or PEX for potable hot and cold, galvanised steel or copper for gas, and stainless steel or PVC for trade waste.

Tool matching: deburring and reaming tools for copper, wheel cutters or saws for PVC, press tools for press-fit fittings, and torque wrenches for gas and mechanical joints.

Drawing scales: 1:100 means 1 mm on the drawing equals 100 mm on site; a 25 mm line at 1:100 represents 2.5 m.

Drawing types: site plan (location and boundaries), floor plan (fixture layout), elevation (heights), section (vertical detail), detail drawing (enlarged component), and isometric (pipe route).

Setting out uses a datum level and grid lines; invert levels (IL) are recorded for drainage, and the cover level minus invert level equals the depth of the pipe.

Levels are transferred with a dumpy level or laser; the backsight reading plus the reduced level of the benchmark equals the height of instrument (HI).

Specifications govern materials, standards and workmanship; where drawings and specifications conflict, the specification usually prevails and the discrepancy is raised as an RFI.

Nominal pipe sizes and gradients on drainage drawings must comply with AS/NZS 3500.2; drawings show fixture units, vent sizes and connection points.

Symbols: solid line for below-ground drainage, dashed line for above-ground or concealed pipework, circles for floor wastes, and arrows for flow direction and fall.

As-built drawings record deviations from design; they are required for handover and for future maintenance and are marked with the plumber's and supervisor's sign-off.

Drainage gradients under AS/NZS 3500.2: DN100 sewer typically 1 in 60 minimum; DN65 and smaller 1 in 60; larger mains may be flatter but must maintain self-cleansing velocity of about 0.6 m/s.

Fixture unit (FU) method: each fixture has a discharge unit value (e.g. WC 4-6 FU, basin 1 FU, shower 2 FU); the total determines the drain and vent size.

Vent types include individual vent, common vent, wet vent and stack vent; every trap must be protected against siphonage by an adequate vent.

Trap seal depth is 25-50 mm for most fixtures; a fixture trap must be accessible for cleaning and self-draining.

Drainage pipework is laid to line and grade with a fall, supported at intervals (typically 1.2 m for PVC horizontal), and tested by water or air test before backfill.

Water test for drainage: the section is filled to the highest point and held for at least 15 minutes; an air test uses 35 kPa for 5 minutes with no drop.

Floor waste and gully traps require a minimum 25 mm water seal and a riser above the surrounding surface to prevent surface water entry.

Fixture installation: set-out heights are measured from finished floor level; WCs are set at 400-450 mm to the top of the pan, basins 850-900 mm, and shower roses about 2000 mm.

Potable water supply is designed to AS/NZS 3500.1; minimum pressure at fixtures is generally 50 kPa at the outlet and maximum static pressure is limited (commonly 500 kPa at the fixture).

Pressure formula: P = rho x g x h; 10 m of water head equals about 100 kPa, so a tank 10 m above a fixture gives 100 kPa static pressure.

Pipe sizing uses the probability of simultaneous demand; flow rates are expressed in litres per second (L/s) and checked against fixture demand tables.

Roof drainage: rainfall intensity (mm/h) x catchment area (m2) gives litres per hour; divide by 3600 for L/s to size gutters and downpipes.

Gutter capacity depends on slope, profile and downpipe spacing; downpipes are sized from the roof area and the design rainfall intensity for the site.

Rainwater tanks require a first-flush diverter, screens, and a backflow prevention device where mains top-up is installed; potable and non-potable lines must be clearly identified.

Stormwater must be discharged to a legal point of discharge (kerb, drainage line or infiltration system) and cannot be connected to the sewer without authority approval.

Roof plumbing requires flashing, sarking and correct lap; all penetrations must be flashed and sealed to prevent water entry.

Gas installations comply with AS/NZS 5601.1 (general) and 5601.2 (LP gas in caravans and boats); work is restricted to licensed gas fitters.

Gas leakage testing: a new installation is tested with air or inert gas at 1.5 times the maximum operating pressure, or as stated in AS/NZS 5601.1, with no pressure drop over the test period.

Gas types: natural gas (methane, SG about 0.6, lighter than air) and LP gas (propane/butane, SG about 1.5-2.0, heavier than air, settles in low points).

Combustion air and flueing: appliances need adequate ventilation, and a flue must terminate away from openings; a CO alarm is a recommended safety control.

Gas pipework is sized by the longest run method or the sizing tables in the standard; pressure drop must not exceed the allowance (typically 0.75 kPa for natural gas at low pressure).

Pipe materials: copper, galvanised steel, and approved PE for underground; joints are brazed, threaded or compression, and no joint is permitted in a wall cavity or inaccessible location.

Isolation: an isolation valve is installed at the meter and at each appliance; the regulator reduces supply pressure to the appliance operating pressure.

Purge and test after installation; never use a flame to search for leaks; use leak detection fluid or an electronic detector.

Heat transfer modes: conduction (through solids), convection (through fluids), radiation (electromagnetic); insulation reduces conduction and convection losses.

Sensible heat changes temperature; latent heat changes state without a temperature change; 1 kg of water requires about 2.26 MJ to vaporise at 100 degrees C.

Refrigeration cycle: compressor raises pressure and temperature, condenser rejects heat, expansion device drops pressure, evaporator absorbs heat; the refrigerant changes phase in each coil.

Refrigerant safety: refrigerants are classified by AS/NZS 1677; recovery is mandatory and venting to atmosphere is prohibited; only licensed technicians handle refrigerant.

Air conditioning load is calculated from building orientation, glazing, insulation, occupancy and internal gains; oversizing causes short cycling and poor dehumidification.

Ductwork sizing uses the equal friction or velocity method; duct velocity affects noise and pressure drop; return air paths must be sized to match supply.

Ventilation: AS 1668.2 sets minimum outdoor air rates for mechanical ventilation; CO2 monitoring is used for demand control.

Heating systems: hydronic heating uses a boiler or heat pump, circulator and radiators or slab coils; water temperature and flow rate determine heat output (Q = m x c x delta T).

A trench is any excavation deeper than it is wide, up to 1.5 m wide; trenches 1.5 m or deeper require shoring, benching or a trench shield, and a competent person inspects daily.

Spotters and barriers are required near public access; trenches are fenced, signed and covered when unattended, and ladders are placed within 9 m of workers.

Before digging, obtain dial-before-you-dig service plans and pothole to confirm live services; maintain clearance from electrical, gas, water and telecom assets.

Soil classification (A, B, C, D) determines the safe batter angle; Type A may stand at 1 in 1, while loose fill requires shoring or a shield.

Pipe laying: prepare a bed of granular material, check invert levels with a laser or level, and maintain grade; haunch and surround the pipe before backfilling.

Backfill in layers of about 150-300 mm, compact each layer and test density; no large rocks against the pipe; warning tape is laid above services.

Bedding and support classes (e.g. Class B sand bedding) are specified for flexible pipe; deflection testing is performed after backfill.

Dewatering and groundwater control prevent trench collapse and pipe flotation; pumps discharge to sediment traps, not directly to stormwater.

Soldering (soft) occurs below 450 degrees C; brazing occurs above 450 degrees C; welding melts the base metal itself.

Copper brazing uses silver or phosphor-copper filler with flux (except for copper-to-copper with phosphor filler); capillary action draws filler into the joint clearance of about 0.05-0.2 mm.

Lead-free solder is required for potable water; flux residues must be removed by flushing and wiping to prevent corrosion and contamination.

Oxy-acetylene safety: acetylene cylinder upright, flashback arrestors on both regulators, no oil or grease on oxygen fittings, and a spark lighter, not matches.

Welding symbols: a fillet weld is shown as a triangle, a butt weld by a V or square edge; the arrow side is below the reference line and the other side above.

Plastic pipe joining: solvent cement for PVC (apply to both surfaces, push and hold), heat fusion for PE (controlled temperature and pressure), and electrofusion for PE in confined areas.

Press-fit and compression joints rely on O-rings and correct insertion depth; the fitting is marked to confirm full insertion, and the joint is pressure-tested.

Weld inspection includes visual, dye penetrant and pressure testing; a failed joint is cut out, not patched, and the cause is recorded.

Communication model: sender, message, channel, receiver, feedback; noise is any interference, and feedback confirms understanding.

Active listening techniques include paraphrasing, asking open questions, summarising and reflecting; these reduce callbacks caused by misunderstood scope.

Documentation: variations, site instructions and delays are recorded in writing and signed; a diary and photo record support claims and quality evidence.

Customer service standards: confirm the appointment window, explain the work and cost before starting, protect floors and furniture, and clean up on completion.

Team roles on site: principal contractor, site supervisor, leading hand and trades; a tool-box talk is used for daily coordination and hazard communication.

Work organisation: job planning uses a task list, material take-off and sequence; critical path tasks are scheduled first, and lead times for materials are confirmed.

Conflict resolution: address the issue not the person, use facts and records, escalate through the supervisor, and follow the site grievance procedure.

Privacy and conduct: customer details are kept confidential, and workplace behaviour is governed by the PCBU's policies and anti-discrimination law.