PGDB Certifying Plumber flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Minimum sewer gradient DN100

The minimum fall for a 100 mm nominal diameter sewer is 1:60 (1.67%), which provides self-cleansing velocity of about 0.6 m/s at full flow.

Trap seal depth

A water seal of 25–50 mm for fixtures and 50 mm minimum for floor wastes prevents sewer gas entry; 75 mm for gully traps.

Vent stack termination

A vent stack must extend at least 150 mm above the roof surface and be at least 3 m from any openable window or air intake.

Fixture unit (FU)

One fixture unit equals 0.03 L/s discharge; a WC is 6 FU, a basin 1 FU, used to size drainage pipes and vents.

Inspection opening location

Inspection openings are required at the base of each stack, at changes of direction greater than 45 degrees, and at intervals not exceeding 15 m.

Minimum fixture pressure

Potable water supply must deliver at least 50 kPa at taps, 100 kPa at showers, and 150 kPa at flush valves under flow conditions.

Backflow prevention device selection

High hazard requires a reduced pressure zone (RPZ) device; medium hazard a double check valve; low hazard a single check valve.

RPZ annual test

Test the reduced pressure zone device annually: check valve tightness, relief valve opens at 14–21 kPa differential, and air inlet functions.

Maximum water velocity

Design cold water pipes for maximum 1.5 m/s and hot water pipes for 1.0 m/s to limit noise, erosion, and pressure surge.

Air gap requirement

A physical air gap of at least twice the pipe diameter (minimum 25 mm) is the only acceptable high-hazard protection for potable supply.

Gas pipe pressure test

Natural gas and LPG piping must be pressure tested at 7 kPa for 10 minutes with no pressure drop, using air or inert gas.

Gas appliance flue clearance

Flue terminals must be at least 500 mm from openable windows, 300 mm from non-openable, 1000 mm from boundaries, and 1500 mm from mechanical air intakes.

Combustion air requirement

Provide 1 m² free area per 250 MJ/h for natural gas appliances and 1 m² per 125 MJ/h for LPG appliances, adjusted for louvre free area.

Gas regulator outlet pressure

Set natural gas regulator outlet to 1.0–1.5 kPa and LPG to 2.75 kPa; lock-up pressure must not exceed 1.25 times set pressure.

Gas leak detection method

Use soap solution or an electronic gas detector to locate leaks; never use a flame. Isolate and repair if leak rate exceeds 0.5 L/h.

Minimum roof slope metal

Metal sheet roofing requires a minimum slope of 5 degrees (1:12); tiles require 15 degrees (1:4); membrane roofs 1.5 degrees (1:40).

Rainfall design intensity

Design stormwater systems using the 1% annual exceedance probability (1 in 100 year) rainfall intensity for the critical duration.

Stormwater pipe gradient

Stormwater pipes must have a minimum gradient of 1:100, providing self-cleansing velocity of at least 0.6 m/s and maximum 3 m/s.

Box gutter overflow

Box gutters require overflow provisions sized for 1.5 times the design flow to handle blockage or extreme rainfall events.

Downpipe capacity DN100

A 100 mm round downpipe can drain approximately 0.20 L/s per square metre of roof area at 100 mm/h rainfall intensity.

Drawing scale conventions

Use 1:100 for floor plans, 1:50 for details, and 1:20 for assemblies; always note the scale and units in millimetres.

Plumbing symbol floor waste

A circle with a cross inside represents a floor waste on plumbing drawings; a triangle indicates a vent.

As-built drawing delivery

As-built drawings must be updated with all changes, invert levels, coordinates, and material types, and delivered within 10 business days of completion.

Specification standard references

Plumbing specifications must reference AS/NZS 3500 series, AS 5601 for gas, AS 2200 for drawing practice, and the NCC.

Notifiable work inspection

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

Certificate of Compliance

A Certificate of Compliance is issued for all regulated plumbing work, includes test results and defects, and must be retained for 7 years.

Continuing professional development

Licensed plumbers must complete 12 hours of CPD per year, including at least 4 hours on regulatory updates and standards changes.

Confined space entry testing

Before entry, test for oxygen 19.5–23.5%, flammable gas below 5% LEL, hydrogen sulphide below 10 ppm, and carbon monoxide below 30 ppm.

Trench shoring requirement

Trenches deeper than 1.5 m require shoring or benching; provide a ladder every 9 m and keep spoil at least 0.5 m from the edge.

Sediment runoff control

Install silt fences and sediment basins to prevent runoff entering stormwater; manage waste segregation and never discharge trade waste to stormwater.

Progress payment timing

Under security of payment legislation, progress payment claims must be paid within 15 business days of the claim being made.

Retention percentage

Retention is typically 5% of contract value held for 12 months, reducing to 2.5% at practical completion to secure defects liability.

Supervision ratio apprentices

One licensed plumber may supervise a maximum of two apprentices on site; direct supervision is required for all notifiable work.

Quality assurance hold point

A hold point in an inspection and test plan requires sign-off by the supervisor or inspector before the next stage of work proceeds.