OBC Plumbing House flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Fixture unit

A dimensionless measure of the probable load a fixture places on the plumbing system; one drainage fixture unit approximates one cubic foot per minute of discharge.

Trap seal

The depth of water held in a plumbing trap, typically 2 to 4 inches, that blocks sewer gas from entering the building through the fixture.

Wet vent

A vent that also carries wastewater from fixtures on the same floor, allowed only where the code permits and sized to handle both air and waste flow.

Developed length

The total measured distance along a pipe centerline, including fittings, used to check trap arm and vent distance limits.

Plumbing permit

An official authorization required before installing or altering plumbing work, posted on site and closed out by inspection before the work is concealed.

Rough-in inspection

The inspection performed after piping is installed but before walls, floors, or ceilings conceal it, verifying size, slope, support, and test pressure.

DWV water test

A test of the drainage and vent system that fills the piping with water to about 10 feet of head and holds it for at least 15 minutes.

Building drain

The lowest piping of a drainage system that receives waste from inside the building and extends 30 inches beyond the exterior wall.

Trap arm length

The distance from the trap weir to the vent connection, limited by trap size: 5 feet for 1-1/4 inch, up to 16 feet for 4 inch.

Vent terminal

The open end of a vent stack that extends at least 6 inches above the roof and away from windows, doors, and air intakes.

Cleanout

An accessible fitting with a removable plug that allows a drain snake to clear blockages, required at stack bases and long horizontal runs.

Static pressure limit

The normal fixture pressure range of 40 to 80 psi; above 80 psi a pressure-reducing valve is required to protect fixtures and piping.

Air gap

The highest form of backflow protection: an unobstructed vertical space between the supply outlet and the flood level rim of the receiving fixture.

Thermal expansion tank

A device installed on a closed water system to absorb the volume increase caused by heating water, preventing excess pressure on pipes and fixtures.

TPR valve

A temperature and pressure relief valve on a water heater that opens automatically and must discharge to a safe, visible point without being capped.

Water closet flush limit

The maximum allowable water use for a toilet, 1.6 gallons per flush, with high-efficiency models using 1.28 gallons or less.

Fixture trap requirement

Every fixture must have a trap with a 2 to 4 inch water seal, and double trapping of a single fixture is prohibited.

Water closet clearance

A toilet needs at least 15 inches from its centerline to a side wall and 21 inches of clear space in front of the bowl.

Dishwasher air gap

A device or high loop on the drain line that prevents sink water from siphoning back into the dishwasher and contaminating clean dishes.

Roof drain sizing

Roof drains are sized from the roof area and the local 100-year, one-hour rainfall intensity, with secondary drainage for overflow.

Grease interceptor

A tank installed outside the building on food service waste lines that traps fats, oils, and grease before the waste enters the sanitary sewer.

Acid-neutralizing sump

A receptacle filled with limestone or marble chips that neutralizes corrosive laboratory or plating waste before it discharges to the drainage system.

Copper tube types

Type K is thickest and used underground, Type L is standard above ground, and Type M is thin wall for above-ground use only.

No-hub coupling

A cast iron pipe joint made with a neoprene sleeve and stainless steel clamp, tightened to the manufacturer's torque specification.

Dielectric union

A fitting that separates copper and steel piping to stop galvanic corrosion caused by dissimilar metals in contact with water.

Solvent cement joint

A PVC or ABS joint made by applying primer and cement, then inserting the pipe fully and twisting a quarter turn to spread the cement.

Fire department connection

A marked exterior connection that lets firefighters pump water into a standpipe or sprinkler system, located near an accessible hydrant.

Standpipe classes

Class I serves firefighters with 2-1/2 inch connections, Class II serves occupants with 1-1/2 inch hose, and Class III provides both.

Medical gas piping

Dedicated piping for oxygen, vacuum, or medical air that requires brazed joints, special materials, and certified installers.

Indirect waste

A drain that discharges through an air gap into a receptor rather than connecting directly, protecting potable water and fixtures from contamination.

Firestopping

An approved listed system that seals a pipe penetration through a fire-rated wall or floor to maintain the assembly's fire-resistance rating.

Joist boring limit

A hole bored in a floor joist must stay within the middle third of its depth and be no larger than one-third of the joist depth.