System allows atmospheric air from outside the building into the piping system to the outlet (or discharge) end of the trap prevents siphonage of a trap seal in fixture traps and allows gravity flow of drainage. The air is supplied through pipes known as “VENTS,” and the pressure on the outlet end of the seal is equal to the pressure on the inlet end.

Types of vent

Individual/Back Vent/Revent -These types of vent are installed in a pipe to vent a fixture trap connected to the vent system above the fixture it serves. It connects directly with any individual waste or group of wastes underneath or at the back of a fixture and extends to either a vent stack or a branch vent.

Vent Stack, Main Vent – Vertical vent pipes are placed primarily to provide air circulation to or from any portion of the building’s drainage system.

Stack Vent, Soil or Waste Vent -The expansion of soil or debris stacks (to the open air) is limited by the highest horizontal branch, drain, or fixture branch connected to the stack.

Stack Venting– continuous venting of a single future or a group of futures directly into the soil or waste stack. Thus, a group of fixtures such as those from a bathroom and a kitchen can be installed without providing individual fixture vents-provided each fixture drain is independently connected to the stack and the water closet and bathtub or shower stall drain enter the stack at the same level.

Unit/Common/Dual/Duplex -It is an arrangement of vents installed in such a way that one pipe serves two (2) traps.

Circuit Vent -A branch vent serves two or more traps and extends from in front of the last fixture connection of a horizontal branch to the vent stack.

Loop Vent/Venting Loop -A vent arrangement for a group of plumbing fixtures consists of a vent pipe which is connected to the waste or soil branch immediately before the first fixture of the group. It is also a branch vent serving two or more fixtures that are connected to the same stack into which the fixtures discharge. A Looped Vent-a type of ventilation system used in fixtures in a room away from a wall or partition.

Looped VentThese types of vent systems are used in fixtures in a room away from a wall or partition.

Relief Vent – A branch connected to a horizontal branch between the fixture branch and the soil or waste stack, the primary function of which is to provide air circulation between the vent stack and the soil or waste stack. It is also an auxiliary vent that connects the vent stack to the soil or waste stack in multistory buildings and is used to equalize pressure differences between them.

Yoke Vent– A pipe leading upward from a soil or waste stack to a vent stack is used to prevent pressure changes in the stack.

Wet Vent – A pipe, usually oversized, which functions both as a fixture branch and as a vent, e.g. a waste pipe that also serves as a vent… Wet vents are used to reduce the vent piping required for a given installation by making individual pipes serve two purposes. Their use simplifies the drainage system and substantially reduces its cost.

Combination Waste and Vent – is a type of ventilation system that functions as both a vent and a waste conductor. It is a specially designed system that enables waste piping, purposely oversized, to serve both as a waste and a vent pipe to avoid excessive pneumatic effects at fixture drains.

Dry Vent – It is a types of vent that transports neither waterborne nor airborne waste.

Crown vent– These types of vents are connected to the crown.

Blind Vent – a vent pipe which terminates at the upper side of the fixture and does not connect to the drainage system, with the intent of cheating.

Fixture Vent – a vent pipe connecting the drainage pipe to another vent pipe or to the atmosphere.

Branch venta vent that connects one or more individual vents to a vent stack or stack vent.

Side Vent – a vent connected to the drain pipe via a fitting at a maximum angle of 45 degrees to the vertical.

Utility Vent -A vent which rises well above the highest water level of a fixture and then turns downward before it connects to the main vent or stack vent.

Local Vent, Local Ventilating Pipe or Vent, or Vapor Vent – is a pipe on the fixture side of the trap through which vapor or foul air is removed from the room or fixture. It conveys foul air from a plumbing fixture to the outer air.

Ejector Vent – A pipe is used to provide air in a sump pit and prevent pressure buildup. It is also a vent pipe used to convey air to a receiving basin that collects the discharge of sanitary waste, called an ejector basin.

Bypass Vent – A vent stack is one that runs parallel to a soil stack (or a waste stack) and is connected to it at frequent intervals.

Continuous Vent – A vertical vent is a combination of a drain, a soil pipe, or a waste pipe to which the vent connects. It is also defined as a vent that is a continuation of and in a straight line with the drain to which it connects.

Vent Extension -a pipe connecting the uppermost drainage branch connection to the atmosphere through the roof.

Vent Header – There is a header (i.e., a horizontal vent pipe) that connects the tops of the vent stacks to the roof. (Note: A header is a pipe with many outlets. The outlets may be parallel and may be at or stack vents at the header; a single vent pipe extends from the header to the open air above 90° to the centerline of the header.