Master Plumber cheat sheet

The adopted plumbing code is a minimum health-and-safety standard; stricter local amendments and written AHJ interpretations govern over the model code text.

Typical permit sequence is permit application, rough-in inspection, and final inspection; work covered before rough-in approval must be uncovered for inspection.

A master plumber license generally authorizes the holder to pull permits, contract for plumbing work, and supervise journeymen and apprentices.

One drainage fixture unit equals roughly 1 cubic foot per minute of flow, or about 7.48 gpm; fixture units drive drain, vent, and water supply sizing.

Boring a nominal 2x4 load-bearing stud: maximum bored hole is 60 percent of stud depth; notching is limited to 25 percent of stud depth on the narrow face.

Unlisted or alternate materials may be used only with a written alternates-and-equivalency approval from the AHJ.

A change in occupancy or use can trigger a requirement to upgrade plumbing to the current code for the new use.

Venting, trap seal, and backflow provisions are health-related code items and are generally not waivable by the owner or contractor.

One psi of pressure equals 2.31 feet of water column; pressure changes about 0.433 psi per foot of elevation.

Static pressure above about 80 psi requires a pressure-reducing valve downstream of the meter, plus thermal expansion control on a closed system.

Common design velocity limits are about 8 fps for cold water and 5 fps for hot water, to limit noise and erosion-corrosion.

Supply sizing uses fixture units, developed length, and available pressure; the longest run and highest outlet govern the result.

Water hammer arrestors are required near quick-closing valves and at the end of long branches; plain air chambers are not accepted as equivalents.

Common code benchmark residual pressure is about 8 psi at showerheads and 15 psi at other fixtures; verify against the adopted code.

Building supply and meter size are derived from total demand fixture units, not from a simple fixture count.

Thermal expansion in a closed system raises pressure quickly; a listed expansion tank or equivalent relief provision is required.

Horizontal drain slope: 2-1/2 inch and smaller at 1/4 inch per foot; 3 through 6 inch at 1/8 inch per foot; 8 inch and larger at 1/16 inch per foot.

Trap seals must be at least 2 inches and not more than 4 inches deep; trap arms have maximum developed-length limits based on pipe size.

Every trap requires a vent except where wet venting, common venting, or another listed code exception applies.

Vent pipe minimum size is generally 1-1/4 inch; vents terminate outdoors at least 6 inches above the roof and away from openings and air intakes.

Cleanouts are required at the base of each stack, at the building drain, at intervals not exceeding 100 feet, and at direction changes greater than 45 degrees.

Drainage pipe must never decrease in size in the direction of flow.

Horizontal drain direction changes use long-sweep fittings or combinations of 45-degree bends; a sanitary tee is not permitted on a horizontal drain.

A backwater valve is required for fixtures draining below the level of the next upstream manhole, or where the code official requires it.

Below-grade drainage that cannot flow by gravity requires a sump with an ejector pump and a vented receiver.

Water closet spacing: centerline at least 15 inches from a side wall, at least 30 inches of clear width, and about 21 to 24 inches of clearance in front.

Federal maximums: water closets 1.6 gpf, urinals 1.0 gpf, showerheads 2.5 gpm at 80 psi, kitchen faucets 2.2 gpm; many states and WaterSense programs are stricter.

Fixtures must be listed and labeled and installed per the manufacturer's instructions, which are enforceable as part of the listing.

Floor drains subject to trap seal evaporation require a trap primer or an approved self-priming trap.

Food-service equipment and ice machines require indirect waste with an air gap or air break, never a direct connection.

Hose bibbs and sillcocks require backflow protection such as a vacuum breaker unless the code provides a specific exception.

Fixtures with slip joints or concealed connections require an accessible panel for repair and removal.

T&P relief valves are typically set at 150 psi and 210 degrees F; the rating must not exceed the tank working pressure and the discharge line cannot be trapped or reduced.

T&P discharge must flow by gravity and terminate safely, commonly 6 inches above the floor or outdoors, and must not be directly connected to the drainage system.

A water heater in a garage requires ignition sources elevated 18 inches above the floor unless the unit is listed as flammable-vapor-ignition-resistant.

Seismic strapping uses two straps, one in the upper third and one in the lower third, with the lower strap at least 4 inches above the controls.

Confined-space combustion air is provided by two permanent openings, commonly sized at 1 square inch per 2,000 Btu/hr for vertical ducts and 1 per 4,000 for horizontal.

Storage above 120 degrees F raises scald risk; where higher storage is used for Legionella control, a master mixing valve must temper distribution.

Hot water lines should be insulated, and recirculation must be balanced so the most remote fixture receives hot water within the code's length or time limit.

Copper water tube: type K is heaviest wall, L is standard, M is lightest; type M is prohibited in some codes for underground or concealed locations.

Copper joining uses lead-free solder with approved flux, brazing for higher temperatures, or listed press fittings installed with the manufacturer's tool.

Dielectric unions or listed transition fittings are required between copper and steel or galvanized pipe to prevent galvanic corrosion.

PVC and ABS serve DWV and inert waste service; CPVC is rated for hot water distribution; PVC is not for hot water.

Solvent cementing requires cleaning, primer where required, cement on both surfaces, a quarter-turn assembly, and full cure before pressure testing.

PEX uses crimp or cinch rings, or expansion fittings on PEX-A; PEX must be protected from UV and sleeved through slabs and penetrations.

Support spacing varies by material: copper 1/2 inch every 6 feet and 1 inch every 8 feet; PVC commonly every 4 feet in small sizes.

No water supply pipe may be smaller than 1/2 inch, and code tables cap the number of fixture units allowed on each branch size.

Gas piping is sized by the longest-length method using connected Btu/hr loads and gas specific gravity; the longest run from the meter governs every branch.

Black steel pipe is the default for natural gas; corrugated stainless steel tubing must be bonded to the grounding electrode system and installed per its listing.

Each appliance requires a shutoff valve in the same room within about 6 feet, a union or flanged connection, and a sediment trap at the inlet.

Typical manifold pressure is 3.5 inches w.c. for natural gas and 10 to 11 inches w.c. for propane.

A common leak test is 10 psi air for 30 minutes with a calibrated gauge, never less than the code-specified minimum test pressure.

Vent connectors slope upward toward the chimney or vent at 1/4 inch per foot, and Category I appliances need a vertical rise before going horizontal.

Type B double-wall vent maintains 1-inch clearance to combustibles; single-wall connectors typically require 6 inches.

Category IV condensing appliances use listed PVC, CPVC, or polypropylene venting pitched back to the appliance for condensate drainage.

Backflow occurs as backsiphonage (supply pressure drops, as in a main break or firefighting) or as backpressure (downstream pressure exceeds supply).

Protection hierarchy from highest to lowest: air gap, reduced pressure zone assembly, pressure vacuum breaker, double check assembly, atmospheric vacuum breaker, hose-bibb breaker.

An air gap must be at least twice the effective pipe diameter and never less than 1 inch above the flood level rim.

An RPZ assembly is testable and required for high-hazard connections; annual testing and reporting to the water authority is typical.

A double check assembly is allowed only for low-hazard, non-toxic connections and is also testable.

An atmospheric vacuum breaker cannot be under continuous pressure for more than 12 hours and must be downstream of the last control valve.

A pressure vacuum breaker must be installed at least 12 inches above the highest downstream outlet and may be under continuous pressure.

Cross-connection programs require device registration, annual testing by a certified tester, and retained repair and test records.

Compute a total fixture-unit load, then apply code tables with developed length and available pressure to size water, gas, and drainage piping.

Developed length is the measured run from the source to the farthest outlet plus fitting allowances; it is not the building's longest room dimension.

Isometric riser diagrams show pipe sizes, fixture connections, slopes, and cleanout locations and govern piping layout over scaled plan measurements.

At 1/4 inch = 1 foot, one quarter inch on paper equals one foot; use a scale rule, never a tape measure, on printed plans.

Takeoff procedure: count fixtures, measure pipe runs, convert to order units, and add an allowance of roughly 5 to 10 percent for waste.

Labor estimates use labor units per fixture or per foot of pipe; overhead, profit, permits, and contingency are added separately.

Document hierarchy: addenda modify the plans and specifications, and work added after contract execution requires a written change order.

Water distribution test: commonly 100 psi hydrostatic for 60 minutes, or working pressure plus 50 psi if higher, with no pressure drop.

DWV test: water test with a 10-foot head for 15 minutes, or an approved air test (commonly 5 psi for 15 minutes) where the code permits.

Gas piping test: commonly 10 psi air for 30 minutes using a calibrated gauge, with results recorded.

Rough-in inspection occurs after piping installation and before concealment; final inspection occurs after fixtures, trim, and testing are complete.

Potable water lines are disinfected after installation or repair, commonly with about 50 ppm chlorine for 24 hours, then flushed and sampled.

Buried pipe requires proper bedding, compaction, and cover, and water and sewer lines must maintain the code's horizontal and vertical separation.

Repairs must use listed materials and methods and must not reduce pipe size or create a cross-connection.

Backflow device records must include make, model, serial number, test results, and the certified tester's identification number.