NPC 2015 Defined Terms

Additional circuit vent means a vent pipe that is installed between a circuit vent and a relief vent to provide additional air circulation.

Air admittance valve means a one-way valve designed to allow air to enter the drainage system when the pressure in the plumbing system is less than the atmospheric pressure. (See Note A-2.2.10.16.(1) of Division B.)

Air break means the unobstructed vertical distance between the lowest point of an indirectly connected soil-or-waste pipe and the flood level rim of the fixture into which it discharges. (See Note A-2.3.3.11.(2) of Division B.)

Air gap means the unobstructed vertical distance through air between the lowest point of a water supply outlet and the flood level rim of the fixture or device into which the outlet discharges. (See Note A-2.6.2.9.(2) of Division B.)

Alloyed zinc means an alloy of zinc having the corrosion resistance and physical properties of an alloy containing 0.15% titanium, 0.74% copper and 99.11% zinc, and so tempered as to be capable of being formed into the shape required for a watertight joint.

Auxiliary water supply means any water supply on or available to the premises other than the primary potable water supply. (See Note A-1.4.1.2.(1).)

Backflow means a flowing back or reversal of the normal direction of the flow.

Backflow preventer means a device or a method that prevents backflow. (See Figure 1.4.1.2.(1)-A in Note A-1.4.1.2.(1).)

Back pressure means pressure higher than the supply pressure.

Back-siphonage means backflow caused by a negative pressure in the supply system. (See Figure 1.4.1.2.(1)-B in Note A-1.4.1.2.(1).)

Back-siphonage preventer (or vacuum breaker) means a device or a method that prevents back-siphonage. (See Figure 1.4.1.2.(1)-C in Note A-1.4.1.2.(1).)

Backwater valve means a check valve designed for use in a gravity drainage system.

Bathroom group means a group of plumbing fixtures installed in the same room, consisting of one domestic-type lavatory, one water closet and either one bathtub (with or without a shower) or one one-head shower.

Branch means a soil-or-waste pipe connected at its upstream end to the junction of 2 or more soil-or-waste pipes or to a soil-or-waste stack, and connected at its downstream end to another branch, a sump, a soil-or-waste stack or a building drain. (See Figure 1.4.1.2.(1)-F in Note A-1.4.1.2.(1).)

Branch vent means a vent pipe that is connected at its lower end to the junction of 2 or more vent pipes, and at its upper end, either to another branch vent or to a stack vent, vent stack or vent header, or terminates in open air. (See Figure 1.4.1.2.(1)-D in Note A-1.4.1.2.(1).)

Building* means any structure used or intended for supporting or sheltering any use or occupancy.

Building drain means the lowest horizontal piping, including any vertical offset, that conducts sewage, clear-water waste or storm water by gravity to a building sewer. (See Figure 1.4.1.2.(1)-F in Note A-1.4.1.2.(1).)

Building sewer means a pipe that is connected to a building drain 1 m outside a wall of a building and that leads to a public sewer or private sewage disposal system.

Building trap means a trap that is installed in a building drain or building sewer to prevent the circulation of air between a drainage system and a public sewer. (See Note A-2.4.5.4.(1) of Division B.)

Care or detention occupancy means the occupancy or use of a building or part thereof by persons who require special care or treatment because of cognitive or physical limitations or by persons who are restrained from, or are incapable of, self-preservation because of security measures not under their control.

Check valve means a valve that permits flow in one direction but prevents a return flow.

Circuit vent means a vent pipe that serves a number of fixtures and connects to the fixture drain of the most upstream fixture.

Class 1 fire sprinkler/standpipe system means an assembly of pipes and fittings that conveys water from the water service pipe to the sprinkler/standpipe system's outlets, is directly connected to the public water supply main only, has no pumps or reservoirs, and in which the sprinkler drains discharge to the atmosphere, to dry wells or to other safe outlets.

Class 2 fire sprinkler/standpipe system means a Class 1 fire sprinkler/standpipe system that includes a booster pump in its connection to the public water supply main.

Class 3 fire sprinkler/standpipe system means an assembly of pipes and fittings that conveys water from the water service pipe to the sprinkler/standpipe system's outlets and is directly connected to the public water supply main as well as to one or more of the following storage facilities, which are filled from the public water supply main only: elevated water storage, fire pumps supplying water from aboveground covered reservoirs, or pressure tanks. The water in this sprinkler/standpipe system must be maintained in potable condition. (See Note A-1.4.1.2.(1).)

Class 4 fire sprinkler/standpipe system means an assembly of pipes and fittings that conveys water from the water service pipe to the sprinkler/standpipe system's outlets and is directly connected to the public water supply main (similar to Class 1 and Class 2 fire sprinkler/standpipe systems) and to an auxiliary water supply dedicated to fire department use that is located within 520 m of a pumper connection.

Class 5 fire sprinkler/standpipe system means an assembly of pipes and fittings that conveys water from the water service pipe to the sprinkler/standpipe system's outlets and is directly connected to the public water supply main and also interconnected with an auxiliary water supply.

Class 6 fire sprinkler/standpipe system means an assembly of pipes and fittings that conveys water from the water service pipe to the sprinkler/standpipe system's outlets and acts as a combined industrial water supply and fire protection system supplied from the public water supply main only, with or without gravity storage or pump suction tanks.

Cleanout means an access provided in drainage and venting systems to provide for cleaning and inspection services.

Clear-water waste means waste water with impurity levels that will not be harmful to health and may include cooling water and condensate drainage from refrigeration and air-conditioning equipment and cooled condensate from steam heating systems, but does not include storm water. (See Note A-1.4.1.2.(1).)

Combined building drain means a building drain that is intended to conduct sewage and storm water.

Combined building sewer means a building sewer that is intended to conduct sewage and storm water.

Combined sewer means a sewer that is intended to conduct sewage and storm water.

Combustible* means that a material fails to meet the acceptance criteria of

Continuous vent means a vent pipe that is an extension of a vertical section of a branch or fixture drain. (See Figure 1.4.1.2.(1)-E in Appendix A.)

Critical level means the level of submergence at which the back-siphonage preventer ceases to prevent back-siphonage.

Dead end means a pipe that terminates with a closed fitting.

Developed length means the length along the centre line of the pipe and fittings. (See Note A-2.5.6.3.(1) of Division B.)

Directly connected means physically connected in such a way that water or gas cannot escape from the connection.

Drainage system means an assembly of pipes, fittings, fixtures, traps and appurtenances that is used to convey sewage, clear-water waste or storm water to a public sewer or a private sewage disposal system, but does not include subsoil drainage pipes. (See Figure 1.4.1.2.(1)-F in Appendix A.)

Dual vent means a vent pipe that serves 2 fixtures and connects at the junction of the trap arms. (See Figure 1.4.1.2.(1)-G in Appendix A.)

Dwelling unit* means a suite operated as a housekeeping unit used or intended to be used by one or more persons and usually containing cooking, eating, living, sleeping and sanitary facilities.

Emergency floor drain means a fixture for the purposes of overflow protection that does not receive regular discharge from other fixtures, other than from a trap primer. (See Appendix A.)

Fire separation* means a construction assembly that acts as a barrier against the spread of fire.

Fire service pipe means a pipe that conveys water from a public water main or private water source to the inside of a building for the purpose of supplying the fire sprinkler or standpipe systems.

Fixture means a receptacle, appliance, apparatus or other device that discharges sewage or clear-water waste, and includes a floor drain.

Fixture drain means the pipe that connects a trap serving a fixture to another part of a drainage system.

Fixture outlet pipe means a pipe that connects the waste opening of a fixture to the trap serving the fixture. (See Figure 1.4.1.2.(1)-H in Appendix A.)

Fixture unit (as applying to drainage systems) means the unit of measure based on the rate of discharge, time of operation and frequency of use of a fixture that expresses the hydraulic load that is imposed by that fixture on the drainage system.

Fixture unit (as applying to water distribution systems) means the unit of measure based on the rate of supply, time of operation and frequency of use of a fixture or outlet that expresses the hydraulic load that is imposed by that fixture or outlet on the supply system.

Flood level rim means the top edge at which water can overflow from a fixture or device. (See Figure 1.4.1.2.(1)-B in Appendix A.)

Flow control roof drain means a roof drain that restricts the flow of storm water into the storm drainage system.

Fresh air inlet means a vent pipe that is installed in conjunction with a building trap and terminates outdoors. (See Note A-2.4.5.4.(1) of Division B.)

Indirect service water heater* means a service water heater that derives its heat from a heating medium such as warm air, steam or hot water.

Indirectly connected means not directly connected. (See Note A-2.3.3.11.(2) of Division B.)

Individual vent means a vent pipe that serves one fixture.

Interceptor means a receptacle that is installed to prevent oil, grease, sand or other materials from passing into a drainage system.

Leader means a pipe that is installed to carry storm water from a roof to a storm building drain or sewer or other place of disposal.

Nominally horizontal means at an angle of less than 45° with the horizontal. (See Figure 1.4.1.2.(1)-J in Appendix A.)

Nominally vertical means at an angle of not more than 45° with the vertical. (See Figure 1.4.1.2.(1)-J in Appendix A.)

Noncombustible* means that a material meets the acceptance criteria of

Occupancy* means the use or intended use of a building or part thereof for the shelter or support of persons, animals or property.

Offset means the piping that connects the ends of 2 pipes that are parallel. (See Figure 1.4.1.2.(1)-K in Appendix A.)

Offset relief vent means a relief vent that provides additional air circulation upstream and downstream of an offset in a soil-or-waste stack. (See Note A-2.5.4.4.(1) of Division B.)

Plumbing system* means a drainage system, a venting system and a water system or parts thereof. (See Figure 1.4.1.2.(1)-L in Appendix A.)

Potable means safe for human consumption.

Private sewage disposal system* means a privately owned plant for the treatment and disposal of sewage (such as a septic tank with an absorption field).

Private use (as applying to the classification of plumbing fixtures) means fixtures in residences and apartments, in private bathrooms of hotels, and in similar installations in other buildings for one family or an individual.

Private water supply system means an assembly of pipes, fittings, valves, equipment and appurtenances that supplies water from a private source to a water distribution system.

Public use (as applying to the classification of plumbing fixtures) means fixtures in general washrooms of schools, gymnasiums, hotels, bars, public comfort stations and other installations where fixtures are installed so that their use is unrestricted.

Relief vent means a vent pipe that is used in conjunction with a circuit vent to provide additional air circulation between a drainage system and a venting system.

Residential full flow-through fire sprinkler/standpipe system means an assembly of pipes and fittings installed in a one- or two-family dwelling that conveys water from the water service pipe to the sprinkler/standpipe system's outlets and is fully integrated into the potable water system to ensure a regular flow of water through all parts of both systems.

Residential partial flow-through fire sprinkler/standpipe system means an assembly of pipes and fittings installed in a one- or two-family dwelling that conveys water from the water service pipe to the sprinkler/standpipe system's outlets and in which flow, during inactive periods of the sprinkler/standpipe system, occurs only through the main header to the water closet located at the farthest point of the two systems.

Riser means a water distribution pipe that extends through at least one full storey.

Roof drain means a fitting or device that is installed in the roof to permit storm water to discharge into a leader.

Roof gutter means an exterior channel installed at the base of a sloped roof to convey storm water.

Sanitary building drain means a building drain that conducts sewage to a building sewer from the most upstream soil-or-waste stack, branch or fixture drain serving a water closet.

Sanitary building sewer means a building sewer that conducts sewage.

Sanitary drainage system* means a drainage system that conducts sewage.

Sanitary sewer means a sewer that conducts sewage.

Service water heater* means a device for heating water for plumbing services.

Sewage means any liquid waste other than clear-water waste or storm water.

Size means the nominal diameter by which a pipe, fitting, trap or other similar item is commercially designated.

Soil-or-waste pipe or waste pipe means a pipe in a sanitary drainage system.

Soil-or-waste stack means a vertical soil-or-waste pipe that passes through one or more storeys, and includes any offset that is part of the stack.

Stack vent means a vent pipe that connects the top of a soil-or-waste stack to a vent header or to outside air. (See Figure 1.4.1.2.(1)-G in Appendix A.)

Storage-type service water heater* means a service water heater with an integral hot water storage tank.

Storey for the purposes of this Code, means the interval between 2 successive floor levels, including mezzanine floors that contain plumbing fixtures, or between a floor level and roof.

Storm building drain means a building drain that conducts storm water and is connected at its upstream end to a leader, sump or catch basin, and at its downstream end to a building sewer or a designated storm water disposal location.

Storm building sewer means a building sewer that conveys storm water.

Storm drainage system means a drainage system that conveys storm water.

Storm sewer means a sewer that conveys storm water.

Storm water means water that is discharged from a surface as a result of rainfall or snowfall.

Subsoil drainage pipe means a pipe that is installed underground to intercept and convey subsurface water.

Suite* means a single room or series of rooms of complementary use, operated under a single tenancy and includes dwelling units, individual guest rooms in motels, hotels, boarding houses, rooming houses and dormitories, as well as individual stores and individual or complementary rooms for business and personal services occupancies.

Trap means a fitting or device that is designed to hold a liquid seal that will prevent the passage of gas but will not materially affect the flow of a liquid.

Trap arm means that portion of a fixture drain between the trap weir and the vent pipe fitting. (See Note A-2.5.6.3.(1) of Division B.)

Trap dip means the lowest part of the upper interior surface of a trap.

Trap seal depth means the vertical distance between the trap dip and the trap weir. (See Note A-2.2.3.1.(1) and (3) of Division B.)

Trap standard means the trap for a fixture that is integral with the support for the fixture.

Trap weir means the highest part of the lower interior surface of a trap. (See Note A-2.2.3.1.(1) and (3) of Division B.)

Vacuum breaker (see back-siphonage preventer).

Vent header means a vent pipe that connects any combination of stack vents or vent stacks to outside air. (See Figure 1.4.1.2.(1)-I in Appendix A.)

Vent pipe means a pipe that is part of a venting system.

Vent stack means a vent pipe that is connected at its upper end to a vent header or that terminates in outside air and is connected at its lower end to the soil-or-waste stack at or below the lowest soil-or-waste pipe connection. (See Figure 1.4.1.2.(1)-G in Appendix A.)

Venting system means an assembly of pipes and fittings that connects a drainage system with outside air for circulation of air and the protection of trap seals in the drainage system. (See Figures 1.4.1.2.(1)-F and 1.4.1.2.(1)-G in Appendix A.)

Waste pipe (see soil-or-waste pipe).

Water distribution system means an assembly of pipes, fittings, valves and appurtenances that conveys water from the water service pipe or private water supply system to water supply outlets, fixtures, appliances and devices.

Water service pipe means a pipe that conveys water from a public water main or private water source to the inside of the building.

Water system means a private water supply system, a water service pipe, a water distribution system or parts thereof.

Wet vent means a soil-or-waste pipe that also serves as a vent pipe and extends from the most downstream wet-vented fixture connection to the most upstream fixture connection. (See Appendix A2.5.8.1.(2) of Division B.)

Yoke vent means a vent pipe that is connected at its lower end to a soil-or-waste stack and at its upper end to a vent stack or to a branch vent connected to a vent stack. (See Note A-2.5.4.3. of Division B.)