NBOPE Journeyperson Plumber flashcards

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

Drainage fixture unit (dfu)

A unit expressing the probable discharge rate of a fixture for sizing drains and vents. Values come from the adopted code table; a water closet is typically 3 to 4 dfu, a lavatory 1 dfu.

Water supply fixture unit (wsfu)

A unit expressing the probable water demand of a fixture for sizing supply piping. Total wsfu is converted to gallons per minute with the code demand curve, not added as gpm directly.

Trap arm length limit

The developed length of pipe between the trap weir and the vent connection. It is limited by code, commonly 5 ft for 1-1/2 in. and 6 ft for 2 in., and must fall no more than one pipe diameter.

Air gap

The unobstructed vertical distance between a potable supply outlet and the flood level rim of a receptacle. It must be at least twice the pipe diameter and never less than 1 in.

Reduced-pressure principle assembly

A testable backflow preventer with two independently acting check valves and a differential relief valve. It protects against both backsiphonage and backpressure and is required for high-hazard connections.

Backsiphonage versus backpressure

Backsiphonage is reverse flow caused by negative pressure in the supply. Backpressure is reverse flow caused by downstream pressure exceeding supply pressure. The protection device must address the applicable condition.

Temperature and pressure relief valve

A safety device required on storage water heaters that opens at a set temperature or pressure. Its discharge pipe must be full size, unobstructed, slope downward, and terminate safely.

Thermal expansion tank

A tank installed on a closed potable water system to absorb the volume increase as water heats. It is required when a check valve, backflow preventer, or pressure-reducing valve closes the system.

Sediment trap (drip leg)

A capped nipple installed at the appliance connection downstream of the shutoff valve to collect debris before it reaches the gas controls. It must be at least 3 in. long.

Combustion air openings

High and low openings that supply air to a fuel-burning appliance in a confined space. They are sized to the appliance input and must not be blocked or reduced by the installer.

Building drain versus building sewer

The building drain is the lowest piping inside the building that receives soil and waste. The building sewer starts about 2 ft outside the foundation and runs to the public sewer or disposal system.

Cleanout requirements

Access points for clearing blockages. They are required at the base of each stack, at the upper end of horizontal drains, at changes in direction greater than 135 degrees, and at intervals set by code.

Wet vent

A vent that also serves as a drain for fixtures on the same floor. The wet portion must be sized for the drainage load, and the vent must be taken above the trap weir.

Air admittance valve

A one-way valve that admits air into the drainage system when negative pressure occurs and seals under positive pressure. It must be installed above the trap weir and remain accessible.

Stack vent versus vent stack

A vent stack is the vertical vent serving a drainage stack. A stack vent is the extension of the soil or waste stack above the highest fixture branch. Both terminate above the roof.

Slope to percent conversion

Percent slope equals fall divided by run, times 100. A 1/4 in. per ft slope is about 2.08%; a 1/8 in. per ft slope is about 1.04%.

Pressure versus head

One psi equals 2.31 ft of water column. A 30 ft column of water exerts about 13 psi. Static head loss must be subtracted from available pressure when sizing supply piping.

Pipe volume formula

Gallons in a full pipe equal 0.0408 times the inside diameter squared in inches times the length in feet. Example: 1 in. ID and 100 ft gives about 4.08 gallons.

Equivalent length of fittings

The straight-pipe length that produces the same friction loss as a fitting. It is added to the measured pipe length to get the total developed length used in sizing.

Rough-in inspection

The inspection after piping is installed but before it is concealed. The system must be tested with water or air and the test witnessed by the code official.

Permit requirement

A plumbing permit is required before installing, altering, or replacing most plumbing systems. Minor repairs such as replacing a faucet generally do not require one, but water heater replacement usually does.

Master versus journeyman license

A journeyman plumber performs work under a master plumber's license. The master holds the license responsible for the permit and the work, and may supervise apprentices.

Copper pipe types K, L, and M

Copper tubing wall thickness designations. Type K is heaviest and used underground; Type L is standard for interior domestic water; Type M is thin wall for above-ground use where allowed.

Solvent cement joint procedure

Cut square, deburr and chamfer, clean with primer, apply cement to both surfaces, assemble with a quarter-turn, hold, and allow full cure before pressure testing.

Threaded steel assembly

Cut square, ream the burr, cut threads with the correct die, apply dope or tape to male threads only, and make up hand-tight plus about 1 to 3 turns.

Trench protective system threshold

OSHA requires a protective system for trenches 5 ft deep or more, or when a competent person identifies a hazard. Access ladders must extend at least 3 ft above the landing.

Flushometer minimum pressure

Flushometer valves require a minimum flowing pressure, often 15 to 25 psi depending on the valve. Undersized branches or pressure drops cause weak or short flushes.

Fixture clearance dimensions

A water closet needs at least 15 in. from centerline to a side wall and 21 in. in front of the bowl. Lavatories need about 15 in. from centerline and 21 in. clearance in front.

Fixture trap distance limits

The trap must be close to the fixture outlet. The vertical distance from the outlet to the trap weir is commonly limited to 24 in., and the horizontal distance is also limited by code.

Dielectric union

A fitting that separates dissimilar metals, such as copper and steel, to prevent galvanic corrosion. It is required where those metals would otherwise be in direct contact in a wet system.

Pressure-reducing valve

A device that lowers incoming water pressure to a safe level, commonly required above 80 psi. It creates a closed system, so a thermal expansion tank is also needed.

Water heater drain pan

A pan required under a water heater where leakage could cause damage. It must be at least 1-1/2 in. deep with a 3/4 in. drain to an approved location.