A–Z Plumbing Terms

Backflow Prevention

A safety device that prevents dirty or contaminated water from flowing back into your clean water supply. Often required by law in certain plumbing setups.

Ball Valve

A quarter-turn isolation valve used to control water or gas flow. Known for its reliability and ease of use.

Boundary Trap / Boundary Shaft

Common in older properties, this creates a water seal between your property’s drains and the main sewer system, usually buried 1–6 metres underground.

Boundary Valve (PLV / PRV)

A pressure limiting or reducing valve that controls water pressure entering your property to prevent damage to pipes and appliances.

Breecher Piece

A pipe fitting that connects hot and cold water lines (usually behind the wall) and allows for water to mix before leaving the tap.

Cistern

The tank that holds and releases water to flush your toilet.

Conversion Taps

Double taps (often in laundries) that allow both a washing machine hose and laundry tub tap to connect to a single outlet.

Duo Valve / Valve Train

A combination of valves connecting the cold water supply to your hot water system. It typically includes an isolation valve, expansion control valve, and tee for the tempering valve.

Earthenware / Terracotta / Vitrified Clay Drain

Old-style clay sewer pipes found in older homes. These have now been replaced with PVC pipes for better durability.

Flushpipe

The pipe that connects the cistern to the toilet bowl (pan).

Floor Trap / Floor Gully

A floor-level drain (usually in bathrooms or laundries) that collects wastewater and connects to the main drainage system.

GIO – Government Inspection Opening

A surface-level sewer inspection shaft located at your property boundary. It’s the connection point between your home’s sewer and the authority’s system.

Gully / ORG (Overflow Relief Gully)

A fitting that prevents sewer gases from entering your home and directs any overflow outside if the main sewer becomes blocked.

Hose Bib / Screw Nose Bib Cock

A garden tap with a threaded outlet that allows a hose to be connected.

HWS – Hot Water Service

Your water heating system. Can be gas, electric, solar, or heat pump operated.

Inlet Valve

Controls the flow of water into your toilet cistern.

Inspection Opening (IO) / Inspection Point (IP)

An access point for plumbers to inspect and clean sewer drains.

KGL or Brass Flare

A brass compression fitting used with copper pipe — typically for gas installations.

Mini Cistern Cock

A small isolation tap that allows you to turn off water to the toilet cistern for servicing.

Nipple

A short brass fitting with male threads on both ends, used to connect copper pipes or brass fittings together.

Pan

The toilet bowl.

Pillar Cock / Pillar Tap

A single, standalone tap with an integrated spout — often found on bathroom basins.

Pilot Light

A small, continuously burning gas flame used to ignite a larger burner in a gas appliance.

PVC Drain

A modern, durable plastic pipe (polyvinyl chloride) used in sewer and stormwater systems.

Rainbank

An automatic system that switches between rainwater and mains water to supply toilets or garden taps — commonly found in newer homes.

Relief Valves (PTR / ECV)

Safety valves on hot water systems that release excess pressure or temperature to prevent damage.

Sacrificial Anode

A magnesium rod inside storage hot water systems that corrodes before the tank itself — extending the life of your system.

Seat

The smooth brass surface inside a tap that the washer seals against to stop water flow.

Stop Tap / Isolation Valve

A valve that controls the water supply to your entire property or a specific fixture. Usually located near the water meter or under sinks.

Tap Washer

A small rubber or fibre disc inside the tap that stops water when the tap is turned off.

Tempering Valve

A device that blends hot and cold water to ensure safe, consistent water temperature (usually set at 50°C for household taps).

Thermocouple

A safety device that detects whether the pilot light is burning. If the flame goes out, it shuts off the gas supply to prevent leaks.

Trap (P-Trap / S-Trap)

The U-shaped section of pipe under sinks, basins, and toilets. It holds water to block sewer gases from entering the home.

Vent Pipe

Allows air into the drainage system, preventing pressure build-up and assisting with wastewater flow.

Water Hammer Arrestor

A device that absorbs sudden pressure changes (water hammer), reducing noise and vibration in pipes.

Water Meter

A device (usually at the front of your property) that measures your water usage and connects your home to the mains supply.

Need a Hand?

Understanding plumbing terms is great — but when something goes wrong, it’s best left to the professionals.
Our licensed plumbers are here to help with everything from leaky taps and blocked drains to hot water repairs and installations.

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