PGDB Certifying Plumber key terms

A dimensionless rating that expresses the likely load a plumbing fixture or appliance places on a drainage or supply system, relative to a standard basin, used to size pipes and vents.

The depth of water held in a fixture trap that stops sewer gases entering a building. It is lost through evaporation, siphonage, or pressure fluctuations, so traps must be vented and kept wetted.

A one-way device that opens to admit air into a drainage stack or branch when pressure drops, protecting trap seals, and closes to prevent foul air escaping. It replaces a vent to open air only where permitted.

Any pipe that carries soil, waste, or trade waste from fixtures to the drain. Its size, gradient, and material are governed by the fixture unit load and the drainage standards applying in the jurisdiction.

The height of the lowest internal point of a pipe or drain at a given location, usually expressed relative to a datum. It sets the gradient between inspection points and confirms whether flow will be by gravity.

A removable access point on a drain or stack, such as an inspection chamber, shaft, or rodding eye, that lets a plumber clear blockages and visually check the line of the pipe.

A valve fitted to a drain to prevent sewage flowing back into a building when the public sewer surcharges. It must be installed where required and kept accessible for maintenance.

The fall of a pipe expressed as a ratio or percentage, such as 1 in 60. Correct gradient gives self-cleansing velocity without excessive slope that would leave solids behind or outrun the water.

Any actual or potential link between a potable water supply and a source of contamination. Cross-connections are the main cause of backflow incidents and must be eliminated or protected by an approved device.

The unwanted reversal of water flow in a supply system, caused either by backpressure from downstream pressure or by backsiphonage when upstream pressure drops. Protection devices are selected by hazard rating.

A testable backflow prevention assembly with two check valves and a relief valve that discharges if pressure between the checks rises, giving high-hazard protection. It needs annual testing and registration.

The unobstructed vertical distance between a water outlet and the flood level of the receiving vessel. It is the highest form of backflow protection because no mechanical part can fail.

A non-testable backflow device with two spring-loaded check valves in series, used for low-hazard protection such as a domestic appliance connection. It does not protect against high hazard.

A valve that blends hot and cold water to deliver a set, stable outlet temperature, protecting users from scalding. It must be commissioned, tested, and where required limited to a maximum delivery temperature.

A pressure surge caused by sudden stopping of water flow, producing banging and stressing pipework and fittings. It is controlled by correct pipe sizing, fastening, and arrestors near quick-closing valves.

A device that lowers incoming supply pressure to a safe, regulated downstream value, protecting fixtures and appliances from excess pressure. It is set at commissioning and may need a strainer upstream.

The air supplied to a gas appliance for complete burning of fuel. Inadequate supply causes carbon monoxide production, so ventilation openings must be sized and kept clear per the installation standard.

A colourless, odourless gas produced by incomplete combustion that is toxic at low concentrations. Gasfitters prevent it through correct air supply, flueing, and appliance servicing, and install alarms where required.

A duct or pipe that carries products of combustion from an appliance to outside air. Its type, termination, and clearance from openings and combustible materials are strictly specified to prevent spillage and re-entry.

Escape of combustion products from an appliance into the room rather than up the flue, often detected by a draught diverter test. Spillage indicates a blocked flue, poor air supply, or adverse pressure.

A pressure test of new or altered gas pipework using air or inert gas to confirm it holds pressure with no drop beyond the permitted allowance before gas is introduced.

The controlled removal of air from gas pipework or of gas from a system before work, so that a flammable mixture cannot form or reach an ignition source. Purge volume is calculated and vented safely.

A device that reduces and holds gas pressure at a steady value for the appliance or installation. Correct operating pressure is verified with a manometer as part of commissioning.

Sheet metal or membrane work that weatherproofs junctions where roofing meets walls, chimneys, valleys, or penetrations. It is lapped and dressed so water is shed outward and never trapped.

A gutter formed with vertical or near-vertical sides and a flat base, usually built into a roof or parapet. It needs careful sizing, fall, and overflow provision because it can hold significant water.

A designed path that safely discharges rainwater when a gutter, downpipe, or tank is blocked or overwhelmed, protecting the building from internal flooding. It must be visible and independent of the main outlet.

A vertical pipe that carries roof water from gutters to the stormwater drain or tank. Its size and number are matched to the roof catchment area and local rainfall intensity.

Temporary storage of roof or site runoff, such as in a tank or basin, that releases it slowly to the public system to limit peak flows. It is often a condition of development approval.

A three-dimensional style of plumbing drawing showing pipe runs, sizes, fittings, and fixtures in a single view. It is used to plan installation and to record as-built services.

A scaled, dimensioned drawing that gives the builder and plumber the information needed to construct the work, including levels, sizes, positions, and details, and is read with the specification.

The written part of the contract documents describing materials, standards, workmanship, and testing requirements that cannot be shown fully on drawings. It takes precedence where drawings are silent.

A documented change to the agreed scope, price, or time of a contract, authorised in writing before the work proceeds. Unrecorded variations are a common source of payment disputes.

A periodic invoice for work completed to a stated date, usually supported by measurement and signed off by the client or superintendent. It is paid under the terms set out in the contract.

A percentage of each payment held back by the client until practical completion or the end of the defects liability period, providing security for defective work. Release conditions are stated in the contract.

A set time after practical completion during which the contractor must return and rectify defects reported by the client at no cost. It begins on the date stated in the contract.

A formal declaration, issued by the licensed plumber or an authorised body, that specified plumbing, drainage, or gas work complies with the applicable regulations. It is required before occupation or use.

Work that regulations require to be notified to the authority and inspected or certified, such as sanitary drainage, gasfitting, or certain water connections. Doing it unnotified is an offence.

Drawings and records revised to show the installation as actually constructed, including any changes from the design. They are handed to the client and authority for future maintenance and locating services.

The ranked order of risk controls from most to least effective: eliminate, substitute, engineer, administrate, then use personal protective equipment. It guides selection of controls in a safe work method statement.

A written document setting out high-risk tasks, the hazards involved, the controls to be applied, and who is responsible. It is prepared before work starts and reviewed on site.

An enclosed or partly enclosed area not designed for continuous occupancy, with restricted entry and exit and potential for hazardous atmosphere, such as a pit or tank. Entry needs a permit and atmospheric testing.

A person who has the training, qualifications, experience, and knowledge to perform a task safely and correctly, and who can identify and control the risks involved. Supervision requirements depend on this status.

A short, documented briefing at the workface covering the day's tasks, hazards, and controls. It keeps the crew aligned, records safety communication, and gives workers a chance to raise concerns.

The oversight of workers and work by a licensed or competent person who directs, checks, and takes responsibility for the quality and safety of the installation, including apprentices and unlicensed assistants.

A test that pressurises a completed pipe system, often with water or air, to a specified level and duration to prove it is leak-free before concealment or handover. Results are recorded.