NC Plumbing Contractor cheat sheet

The NC Plumbing Code is part of the NC State Building Code, adopted by the NC Building Code Council and based on the International Plumbing Code with state amendments.

Local governments enforce the state code by issuing permits, reviewing plans, and performing inspections; they may not adopt local plumbing requirements less stringent than the state code.

A plumbing contractor license is issued to a business entity and is tied to a qualifying individual who met the experience requirement and passed the licensing examination.

P-1 is the unlimited plumbing contractor classification; P-2 is a limited classification restricted to one- and two-family residential plumbing work.

Contracting for plumbing work without a valid license is a criminal offense in NC and also bars the unlicensed party from recovering compensation in court for the work.

A permit must be obtained before work begins, and rough-in and final inspections must be passed; concealing work before inspection is a violation.

An owner may perform plumbing work on a single-family residence the owner occupies, which is the principal owner-builder exemption from licensing.

The licensing board may suspend, revoke, or refuse to renew a license for code violations, incompetence, fraud, or abandonment of a project.

'Plumbing' covers the pipes, fixtures, appliances, and appurtenances used to supply water and to remove waterborne wastes, including the connected drainage and venting.

A fixture unit is a numerical value representing the load a fixture imposes on the drainage system or the probable demand it places on the water system.

Flood level rim is the top edge of a fixture or receptacle from which water overflows onto the floor or surrounding area.

Backflow is the reversal of normal flow direction in a piping system; a cross-connection is any actual or potential link between potable and nonpotable systems.

Minimum sizes: no drainage pipe may be smaller than 1-1/4 inch, and no water-supply pipe may be smaller than 1/2 inch.

Pipe, fittings, and fixtures must be listed and bear the standard or code marking of a recognized testing agency before installation.

Penetrations of fire-resistance-rated assemblies by plumbing pipe must be protected with listed firestopping materials and methods.

Water service piping must be installed below the local frost depth and protected from physical damage, corrosion, and structural loading.

Slope: 1/4 inch per foot for pipe 2-1/2 inches and smaller; 1/8 inch per foot for pipe 3 inches and larger.

Trap seal must be at least 2 inches and not more than 4 inches deep, and the trap arm may fall no more than one pipe diameter.

Maximum trap arm length from fixture outlet to vent: 1-1/4 in = 5 ft, 1-1/2 in = 6 ft, 2 in = 8 ft, 3 in = 12 ft, 4 in = 16 ft.

Every trap must be vented; an individual vent must be at least 1-1/4 inch nominal and not less than one-half the diameter of the drain it serves.

A vent terminal must extend at least 6 inches above the roof and be located away from windows, doors, and outdoor air intakes.

Cleanouts are required at the base of each stack, at the end of each horizontal drain, at intervals not over 100 feet, and at changes of direction greater than 45 degrees; cleanout size matches the pipe.

A backwater valve is required where a fixture's flood level rim is below the elevation of the next upstream manhole cover.

S-traps, double-trapped fixtures, and traps that depend on a vent located downstream of the trap are prohibited.

Water closet drains must be at least 3 inches; horizontal wet venting is permitted for bathroom groups within the limits of the vent tables.

Static pressure at fixtures may not exceed 80 psi; where it does, a pressure-reducing valve is required. Minimum flow pressure at a fixture is 8 psi.

Building water service minimum size is 3/4 inch; fixture supply minimum is 1/2 inch; water heater connectors are 3/4 inch minimum.

A thermal expansion tank or device is required where a check valve, pressure-reducing valve, or backflow preventer creates a closed system.

Storage water heaters require a temperature and pressure relief valve set at or below 210 degrees F and 150 psi; the discharge pipe is full size, gravity-drained, terminates not more than 6 inches above the floor or outside, and has no threads or cap.

A water heater installed where leakage would cause damage must sit in a watertight pan with a drain to an approved location.

Size distribution piping by converting fixture loads to water-supply fixture units, reading the demand in gpm from the tables, then selecting pipe size for the developed length.

Keep flow velocity in distribution mains near 8 fps to limit noise and erosion; 1 psi of pressure equals 2.31 feet of water column.

Water closet clearance: at least 15 inches from centerline to any sidewall or partition and at least 21 inches clear in front of the bowl.

Maximum fixture flow rates: water closet 1.6 gpf, urinal 1.0 gpf, showerhead 2.5 gpm at 80 psi, lavatory and kitchen faucet 2.2 gpm, public lavatory faucet 0.5 gpm.

Minimum fixture drain sizes: lavatory 1-1/4 inch, kitchen sink 1-1/2 inch, shower 2 inches, floor drain 2 inches, water closet 3 inches.

A clothes washer standpipe must be at least 2 inches and must terminate 18 to 30 inches above the trap weir.

Food-handling sinks, sterilizers, and similar equipment must drain through an indirect waste with an air gap or air break, never a direct connection.

Floor drains and other infrequently used traps need trap primers or an approved means to keep the seal from evaporating.

Showers require pressure-balancing or thermostatic mixing valves, and the delivered temperature is limited to about 120 degrees F.

Fixtures must be smooth, nonabsorbent, accessible for cleaning, securely fastened, and free of concealed slip joints.

Minimum air gap is the greater of 1 inch or twice the effective opening of the outlet, measured vertically above the flood level rim.

Protection hierarchy: an air gap gives the highest protection; a reduced-pressure-zone assembly (RPZ) is required for high hazards; double-check and pressure vacuum breakers serve low hazards; hose bibbs use atmospheric vacuum breakers.

An RPZ must be installed above grade, accessible for testing and repair, and not in a pit subject to flooding; it is tested with a differential pressure gauge and retested on the required schedule.

No direct connection is permitted between potable water and irrigation, boiler, chemical-injection, or fire-sprinkler systems without listed backflow protection.

Grease interceptors must be sized for the fixture flow, vented, accessible for cleaning, and must receive only kitchen waste, not sanitary or storm flow.

Water softeners and other treatment devices require backflow protection and a bypass for servicing.

Indirect waste receptors must be sized to receive the discharge and must be protected by an air break, with the waste pipe discharging above the flood level rim.

On an isometric riser diagram, vertical lines are risers and the angled lines represent horizontal runs with 45-degree offsets read along the two horizontal axes.

Gallons = cubic feet x 7.48; pipe volume in gallons per foot: 1/2 in = 0.010, 3/4 in = 0.023, 1 in = 0.041, 1-1/2 in = 0.092, 2 in = 0.163, 4 in = 0.653.

Pressure and head: feet of head = psi x 2.31; psi = feet of head / 2.31.

Fall = run x slope; invert elevation = rim elevation minus depth; compare invert elevations to confirm the required grade between structures.

Trench cubic yards = length x width x depth (all in feet) / 27, plus allowances for bedding, backfill, and swell.

Selling price = total cost / (1 - desired margin); markup on cost is not the same number as margin on the selling price.

Estimating allowances commonly run 5 to 10 percent waste on pipe plus a fitting allowance based on the fitting count.

At a scale of 1/4 inch = 1 foot, one quarter inch measured on the drawing represents one foot of actual pipe run.

A claim of lien in NC must be filed within 120 days after the claimant last furnished labor or materials to the project.

On projects where a lien agent is designated, a subcontractor must give notice to the lien agent within 15 days after first furnishing labor or materials.

North Carolina employers with three or more employees must carry workers' compensation insurance.

Extra work must be authorized by a written, signed change order before it is performed; unwritten extras are difficult to collect.

Bond types: bid bond guarantees the award, performance bond guarantees completion, payment bond protects subcontractors and suppliers.

Retainage is commonly 5 percent of each payment and is released at substantial completion or after the punch list is closed.

Common contract types are lump sum, unit price, and cost-plus or time-and-materials; each shifts risk between owner and contractor differently.

Subcontracts flow down the prime contract's schedule, insurance, indemnity, and scope provisions to the subcontractor.