Plumbing & HVAC Terminology

A Helpful Guide from Emergency Plumbing Heating Air

Access Chamber

An opening into the ground from which drains can be inspected and rodded or cleaned out, both towards and away from a building, also acting as a junction into which the drainage from other plumbing fixtures may discharge into the horizontal drain.

Accessible

In reference to a plumbing fixture, appliance, equipment or connection. It is easily reached, though the use of tools may be required to remove an access panel or open a door.

Air Break

A physical separation between any pipe and receptor through the free atmosphere. The separation may be below the flood level of the receptor but above the trap seal.

Air Gap

A physical separation between a safe drinking water system and above the flood level of the receptor. The separation should be at least twice the supply pipe diameter, but never less than 25 millimetres (1 inch).

Authority

An individual official, board, ministry, or other political entity established and authorized by governmental sanction or a specific law enacted by a governing body that confers statutory powers to formulate and enforce a code of practice for plumbing.

Backflow

The reversing of the normal flow of water or other substances into the drinking-water distribution system from any unintended source.

Backpressure

The reversing of normal flow resulting from a pressure downstream that is higher than the supply pressure in the distribution piping of a drinking-water supply system.

Backsiphonage

The reversing of normal flow resulting from negative or subatmospheric pressures in the distribution piping of a drinking-water supply system.

Backwater Valve

A device for preventing sewage or drainage water from flowing back into a building in the event of flooding or sewer blockage.

Black Water

Combined domestic effluent, including liquid and solid human body waste, and the water discharged from toilet usage.

Building Drain

The lowest part of a building drainage system where the drainage pipes meet and convey the discharge from within the walls or footings of any building to the building sewer. Also called house drain. See also combined building drain; sanitary building drain.

Building Sewer

That part of the horizontal piping of a drainage system that extends from the end of the building drain and that receives the discharge of the building drain and conveys it to a public sewer, private sewer, private sewage disposal system or other point of disposal. Also called house sewer. See also combined building sewer; sanitary building sewer; storm building sewer.

Building Subdrain

That portion of a drainage system that does not drain by gravity into the building sewer. Also called house subdrain.

Check Valve

A valve that allows the flow of a liquid in only one direction but closes when the normal direction of flow is reversed.

Cistern

A vessel open at the top to the atmosphere used to hold a supply of cold drinking water.

Cleaning Eye

Same as access chamber.

Colour Marking

The marking of pipes and fittings with different colours to designate the application of the product and to assist installers in identification and prevention of cross-connections.

Combined Building Drain

A building drain that conveys both sewage and storm water or other drainage.

Combined Building Sewer

A building sewer that conveys both sewage and storm water or other drainage.

Conservation

The preservation and protection of natural resources.

Corrosion

A surface reaction causing a gradual erosion of the material affected.

Cross-Connection

Any physical connection or arrangement between two otherwise separate piping systems or containment means, one of which contains potable water, and the other water or fluid of unknown or questionable safety.

Disinfection

Killing or rendering harmless microbial contaminants by chemical or physical processes.

Downpipe or Downspout

A vertical drainage pipe for conveying storm water from the roof or gutter drains.

Drain

Any pipe that carries waterborne waste in a building drainage system. See also building drain; storm drain; subsoil drain.

Drainage System

All the piping within public or private premises that conveys sewage or other liquid wastes to a point of disposal. It does not include the mains of a public sewer system or a public sewage treatment or disposal plant.

Drain Cock

A valve, usually installed in the lowest portion of a piping system or vessel, that controls the flow of liquid from the system or vessel. Also called drain valve.

Dual System

A situation in which a second plumbing system is installed alongside the system for the provision of drinking water. An example is a potable drinking water system and a greywater system in the same facility.

Electrolysis

A chemical change that occurs when an electric current is generated by the connection of two different metals, either directly or via an electrolyte solution.

Fixture

See plumbing fixture.

Fixture Unit

An arbitrarily chosen scale or quantity that represents the load of a fixture on a drainage system. One fixture unit was originally established as 7.5 imperial (UK) gallons = 9 US gallons = 34 litres per minute discharge by gravity through a fixture.

Flammable Waste

Waste that is easily ignited and will burn.

Float Valve

A valve that operates by means of a bulb or ball floating on the surface of a liquid in a tank or container. The rise and fall action operates a lever, which opens and closes the valve.

Flushometer Valve

A device activated by direct water pressure to discharge a predetermined quantity of water to fixtures for flushing purposes.

Frost Protection

Methods, such as burial or insulation, used to protect against freezing of pipes or fixtures.

Grease Interceptor

A device, usually outside a building, that retains grease and prevents it from passing into the sewerage system.

Grease Trap

A grease interceptor installed inside a facility, usually near the grease-producing fixtures.

Green Water

Reclaimed water that has been treated to a standard, suitable for general domestic non-potable applications. It may be identified through inclusion of a green dye and supplied through a dedicated colour-coded pipework system.

Greywater

Water that has already been used for bathing, washing, laundry or dishwashing, but does not contain excreta.

Indirect Connections

Waste piping that discharges into a receptor or interceptor through an air break or air gap into the drainage system.

Industrial Waste

Liquid or waterborne waste from industrial or commercial processes.

Inspection Chamber

Same as access chamber.

Interceptor

A device used to separate deleterious, hazardous or undesirable matter from normal wastes, retaining it while permitting normal sewage or liquid wastes to discharge into the drainage system by gravity.

Liquid Waste

The discharge from any fixture, appliance, or appurtenance in connection with a plumbing system that does not receive faecal matter.

Manhole

Same as access chamber.

Mixing Valve

A valve or faucet that mixes liquids using automatic or manual regulation.

Negative Pressure

Pressure below the external atmosphere pressure, taking into account the local elevation.

Non-Return Valve

Same as check valve.

Oil Trap

An interceptor used to retain oil and prevent it passing into sewers.

Overflow System

An outlet or receptacle designed to collect surplus liquids after the desired amount has been received.

pH

The negative logarithm (base 10) of the hydrogen concentration. On the scale of 0 to 14, 7 is neutral, lower numbers are acidic, and higher numbers are basic.

Plumbing Fixture

A general term applied to any plumbing receptacle, device or appliance that can be temporarily or permanently fixed in place. It is connected to the drinking-water supply or to the drainage system either by an indirect or direct connection.

Potable Water

Same as drinking-water.

Pressure Reduction Valve

A device that regulates pressure in liquids or gases by reducing a higher pressure to a definite lower pressure, maintaining the liquids or gases at a constant pressure.

Pressure Relief Valve

A safety valve that is held closed by a spring or other means and automatically relieves the pressure in excess of its setting. See also temperature and pressure relief valve.

Reclaimed Water

Water that has been treated so that its quality is suitable for particular specified purposes, such as irrigation, toilet flushing, or possibly drinking. Also called recycled water.

Roof Drainage

Conveyance of rainwater from a sloping roof by gutters and downspouts, or from a vertical roof by pipe, to a surface water sewer or suitable soakaway.

Safe or Potable Drinking Water

Water that is intended for human consumption and suitable for all usual domestic uses, complying with the requirements of the WHO Guidelines for Drinking-water Quality or appropriate national standards established by the regulating authority.

Sanitary Building Drain

A building drain that conveys only domestic or industrial waste, not storm water.

Sanitary Building Sewer

A building sewer that conveys only domestic or industrial waste, not storm water.

Sanitary Sewer

A sewer intended to receive only domestic or industrial waste, not storm water.

Sewage

Liquid waste and wastewater generated by residential and commerical sources and carried in sewers.

Sewer

A channel or conduit, usually subterranean, for carrying off water and waste matter, such as surface water from rainfall, household waste from sinks and baths, and wastewater from industrial works. See also building sewer; sanitary sewer.

Sewerage

The works comprising a sewer system, pumping stations, treatment works and all other works necessary to the collection, treatment and disposal of sewage.

Sewer System

System including a building sewer, a private or public sewer, and a private or public sewage disposal system

Stop Valve

A key control valve capable of shutting off the whole plumbing system that is under mains pressure.

Storm Drain

The part of the horizontal piping and its branches that directs subsoil and surface drainage from areas, courts, roofs, or yards to a building or storm sewer.

Storm Water Drainage

Drainage of rainwater from roofs, courtyards and paved areas and conveying it away from buildings to a place of disposal.

Subsoil Drain

A drain that collects subsurface or seepage water and conveys it to a place of disposal.

Temperature and Pressure Relief Valve

A device that controls both temperature and pressure, releasing water to atmosphere at predetermined settings. See also pressure relief valve.

Trap

A device or fitting that provides a liquid seal to prevent the emission of sewer gases without materially retarding the flow of sewage or wastewater through it.

Vent

Any pipe provided to ventilate a plumbing system in order to prevent backpressure and trap siphonage, or to equalize the air pressure within the drainage system.

Waste

See liquid waste; industrial waste.

Wastewater

The spent or used water of a community, including from residences and commercial buildings, and any surface water or storm water that contains dissolved or suspended matter

Water Closet

A water-flushing device or fixture designed to receive human waste directly from the user and discharge it to the drainage system.

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