NCCER Plumbing flashcards

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

Minimum drainage slope

Horizontal drainage pipe must slope at least 1/4 in. per foot for 2-1/2 in. and smaller pipe; 1/8 in. per foot is allowed for 3 in. and larger pipe only where the code permits adequate velocity.

Drainage fixture unit (dfu)

A unit that expresses the probable waste load of a fixture. A water closet is typically 3 dfu, a lavatory 1 dfu, and a floor drain 2 dfu; total dfu from the code table gives the drain size.

Trap seal depth

The water seal in a fixture trap must be 2 to 4 in. deep. The trap must be level and vented, and the trap arm length from the trap weir to the vent is limited by pipe size.

T&P relief valve discharge

The temperature and pressure relief valve on a water heater must discharge to within 6 in. of the floor or outside, must not be capped or reduced, and must be set to the tank's rated pressure and temperature.

Copper tube types

Type K is thickest (green), Type L is medium (blue), and Type M is thinnest (red). Type L is common for plumbing; Type M is limited to above-ground, non-embedded use.

Water closet rough-in

The distance from the finished wall to the center of the closet drain, commonly 12 in. (10 in. and 14 in. also exist). The closet flange must be flush with or slightly above the finished floor.

No-hub coupling torque

Cast iron no-hub couplings must be tightened to the manufacturer's torque specification, commonly 60 in.-lb, using a calibrated torque wrench, with the sleeve centered on the joint.

PVC solvent weld cure time

After priming and cementing, the joint must cure before pressure testing. Cure time depends on pipe size and temperature; 1-1/2 in. pipe at 60–100°F typically needs about 15 minutes.

Trench protective system

A trench 5 ft or deeper requires a protective system such as sloping, shoring, or shielding unless it is in stable rock. Spoil and equipment must be kept at least 2 ft from the edge.

Confined space entry limits

Before entry, test the atmosphere: oxygen must be 19.5–23.5%, flammable gas below 10% of the lower explosive limit, and hydrogen sulfide below 10 ppm. A permit is required.

Hot work fire watch

Soldering, brazing, and cutting require a fire watch. Keep combustibles at least 35 ft away, have an appropriate extinguisher, and monitor the area after the work ends.

Plumbing drawing symbols

A circle with a cross is a floor drain, a square with a diagonal is a cleanout, a triangle is a vent through the roof, dashed lines are concealed pipe, and solid lines are exposed pipe.

MasterFormat Division 22

Division 22 of MasterFormat covers plumbing. Division 21 is fire suppression and Division 23 is HVAC. Specifications govern materials, testing, and submittals and take precedence over drawings when they conflict.

Architect's scale

A scale such as 1/4 in. = 1 ft means 1/4 in. on the drawing equals 12 in. actual. Use an architect's scale for building plans; an engineer's scale is used for site and civil drawings.

Water hammer cause

Water hammer is caused by sudden valve closure that sends a pressure wave through the pipe. Fix it with air chambers, water hammer arrestors, or by replacing worn valves and securing loose pipe.

Meter test for supply leak

With all fixtures off, a water meter that continues to move indicates a supply leak. A dye test in the tank identifies a leaking flapper, and a smoke test locates a broken vent or sewer line.

Sewage ejector basin

A sewage ejector basin must be vented and the pump controlled by a float. A simplex system requires an alarm. Check the check valve and float before replacing the pump.

First-hour rating

The first-hour rating (FHR) of a water heater is the gallons of hot water it can deliver in one hour. It depends on tank volume, recovery rate, and input BTU, and must meet peak demand.

Thermal expansion tank

A closed water system with a backflow preventer requires a thermal expansion tank sized to the system volume and temperature rise. The tank precharge is set to the system's static pressure.

Legionella control temperatures

Store hot water at 140°F or higher and use a mixing valve to deliver 120°F or less at the fixture. Flush unused fixtures and eliminate dead legs in the piping.

Gas pipe sizing method

Use the longest-length method from the code's gas tables. The longest run from the meter to the farthest appliance sets the size for the total load, and each branch is sized for its own load and length.

Combustion air openings

A confined space requires two permanent openings, one high and one low. Free area is commonly 1 sq in. per 1,000 BTU/hr for a direct opening and 1 sq in. per 2,000 BTU/hr for a vertical duct.

Backdrafting test

Test for spillage at the draft hood with a mirror or smoke. A blocked flue, a tight house, or an undersized vent can cause backdrafting, which is a carbon monoxide hazard.

Water supply fixture units

Water supply fixture units (wsfu) differ from drainage units: a flush-tank water closet is 2.5 wsfu, a flushometer water closet 10 wsfu, a lavatory 1 wsfu, and a bathtub 4 wsfu.

ADA water closet clearance

An accessible water closet has its centerline 16–18 in. from the side wall and a seat height of 17–19 in. A lavatory requires 27 in. of knee clearance and 8 in. of depth.

Pressure-reducing valve threshold

A pressure-reducing valve is required when the supply pressure exceeds 80 psi. The typical delivered pressure is 45–60 psi, verified with a pressure gauge.

Soldering versus brazing

Soldering joins pipe below 840°F and uses lead-free solder for potable water. Brazing is above 840°F and uses a filler such as Sil-Fos for high-temperature or medical gas work.

PEX support and UV

PEX must be protected from UV light, supported every 32 in. horizontally, and kept at least 12 in. from a heat source. Use a crimp, clamp, or expansion system per the manufacturer.

Critical path method

The critical path method (CPM) identifies the longest sequence of dependent tasks in a schedule. A delay on the critical path delays the entire project.

Punch list

A punch list is a list of incomplete or defective work identified at substantial completion. The contractor must correct the items before final payment and closeout.

Shower pan preslope

A shower pan requires a preslope of 1/4 in. per foot under the waterproof membrane, a clamping drain, and a weep hole path. The finished tile slope is also 1/4 in. per foot.

Vent terminal height

A vent must extend at least 6 in. above the roof, or 12 in. where snow accumulates, and at least 3 ft from a window or air intake. It must be at least 10 ft from a chimney.