ID Plumber cheat sheet

Permit required before installation, alteration, or repair of a plumbing system, except minor repair work such as stopping leaks, clearing stoppages, or replacing a faucet washer, per typical code administrative chapters.

Permit applications list the scope, owner, contractor license number, and use; work must start within 180 days of issuance and may be extended by written request before expiration.

Inspections occur at defined stages: rough-in (before concealment), underground, water piping, drainage and vent systems, gas piping pressure test, and final.

Plumbing contractor of record must be licensed; journeyman and master licenses are issued by the state or local authority having jurisdiction (AHJ), and unlicensed practice is a violation.

The AHJ may order work stopped when it is contrary to code, unsafe, or performed without a permit; stop-work orders remain until conditions are corrected and re-inspected.

Definitions: "shall" is mandatory, "should" is recommended, "may" is permissive. Plumbing system includes water supply, fixtures, drainage, vents, traps, and gas piping where adopted.

Code editions are adopted locally; the AHJ enforces the adopted edition, and where requirements conflict the more stringent provision applies.

Appeals of AHJ decisions go to the board of appeals within a stated period; work may not proceed while an appeal is pending unless the AHJ authorizes it.

Minimum plumbing facilities are counted by occupancy use and occupant load; separate facilities are required where the occupant load of each sex exceeds the threshold in the code table.

Fixture units (FU) are the common currency linking fixture counts to pipe sizing: 1 FU = 1 cubic foot per minute (7.5 gpm) of drainage load, and supply FU values differ from drainage FU values.

Structural penetrations: holes in solid sawn joists are limited to one-third the depth, not in the middle third of the span; notches on the tension side are limited to one-sixth the depth.

Bored holes in studs must be at least 5/8 inch from the edge, and notching is limited to 25 percent of the stud width, to preserve structural capacity.

Plumbing piping in a wall of a fire-resistance-rated assembly must maintain the required membrane penetration protection; plastic pipe may require firestopping or listed assemblies.

Water and drainage pipe cannot be installed in the same trench with electrical conductors unless separated per the electrical code; water pipe below drainage pipe with proper clearances where crossing.

Piping must be protected from freezing and from corrosion; exterior piping subject to damage requires shielding plates or concrete encasement where within the specified distance of the finished surface.

Excavations for underground piping require proper slope, bedding, and compaction; thrust blocks or restrained joints are required at bends and tees on pressurized mains.

Water closets: maximum flush volume 1.6 gallons per flush; public and commercial settings often use 1.28 gpf or high-efficiency models; urinals limited to 1.0 gpf or less.

Lavatory faucets limited to 2.2 gpm at 60 psi, kitchen faucets 2.2 gpm, showerheads 2.5 gpm at 80 psi; metering and public lavatory faucets have lower limits.

Water heaters require a temperature and pressure relief valve with the drain terminating within 6 inches of the floor or to the exterior, and a full-open valve with no reduction in size.

A thermal expansion tank is required on a closed system with a backflow preventer or check valve, sized to the system volume and temperature rise.

Water heater drain pans are required where leakage could cause damage; pan drains must discharge by gravity to an approved location and are not permitted to connect directly to a drainage system.

Fixture clearances: water closets require 15 inches from centerline to side wall and 30 inches of clear space in front; lavatories require 15 inches from centerline to a side wall.

Floor drains require a trap with a minimum 2-inch trap seal, and trap primers are required where the trap is subject to evaporation.

Backflow protection: air gaps, vacuum breakers, and reduced-pressure zone assemblies are selected by hazard level; hose bibbs require vacuum breakers.

Minimum residual pressure: 8 psi at fixtures during flow for flush tanks and 15 psi for flushometer valves; static pressure must not exceed 80 psi, requiring a pressure-reducing valve above that.

Developed length includes the building supply plus the longest run to the most remote outlet; add equivalent length for fittings and valves.

Sizing uses fixture units converted to gallons per minute demand curves, then pipe size from tables using velocity limits (typically 8 fps for cold, 5 fps for hot).

Water service: minimum 3/4 inch for a single dwelling; larger for combined services, with a full-open main shutoff valve and a meter where required.

Hot water distribution: maximum developed length from source to fixture is limited (often 50 feet without a recirculation system), and hot and cold lines require minimum separation from each other.

Shock arrestors or air chambers are required at quick-closing valves and flushometer installations to absorb water hammer.

Backflow prevention assemblies must be tested at installation and annually by a certified tester, with records provided to the water purveyor.

Water piping must be supported at intervals based on pipe material and size, and must slope to drain at low points with drain valves.

Drainage slope: 2-inch and smaller pipe at 1/4 inch per foot; 3-inch at 1/8 inch per foot minimum; 4-inch and larger at 1/8 inch per foot minimum, with no allowance for flat or negative slope.

Drainage fixture unit tables assign values by fixture type; a water closet is typically 3 FU, a lavatory 1 FU, a bathtub 2 FU, and a floor drain 2 FU.

A building drain is the lowest piping that receives soil and waste inside the building; a building sewer is the pipe from the building drain to the public sewer or private disposal.

Vent stack sizing is based on drainage fixture units and stack length; a vent must terminate at least 6 inches above the roof and at least 3 feet from an operable window or air intake.

Each trap requires a vent; the distance from a trap to its vent is limited (typically 3 to 5 feet for 1.5-inch traps) and varies with trap size and slope.

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

Storm drainage is sized by rainfall intensity and roof area; 1 inch of rainfall per hour on 1 square foot of roof equals 0.0104 cubic feet per second.

Storm water must not connect to the sanitary drainage system where separate systems exist; downspouts and area drains require traps or relief where subject to freezing.

Every fixture except those with integral traps must be trapped; traps must have a liquid seal of at least 2 inches and at most 4 inches.

Each trap must be self-cleaning, of the same nominal size as the fixture drain, and installed level; no double trapping or trap on a trap.

Grease interceptors are required for commercial kitchens and are sized by fixture units or by the formula using flow rate, retention time, and storage factor; they need a vent and access cover.

Sand and oil interceptors are required for vehicle service areas and similar dischargers; the interceptor must be accessible and sized to the discharge.

Special wastes such as photographic chemicals, dental amalgam, and acid wastes require neutralization or separation before entering the drainage system.

Traps subject to evaporation, such as floor drains in unused areas, require trap primers to maintain the seal and prevent sewer gas entry.

A trap arm may not have more than one trap on it, and the trap arm must be vented before it connects to another fixture drain.

Interceptors must be installed so that the flow passes through the interceptor before connecting to the building drainage system, with no bypass.

Indirect waste receptors must be of a type that prevents backflow, with an air gap of at least twice the effective opening of the drain or 1 inch, whichever is greater.

Indirect wastes are required for food service equipment, sterilizers, water treatment backwash, and similar fixtures that cannot be directly connected to drainage.

Gray water is wastewater from lavatories, showers, bathtubs, and laundry; it does not include toilet or kitchen sink waste.

Gray water systems require a permit, a dual-pipe system with purple or marked pipe, and separation from potable water by air gaps or reduced-pressure assemblies.

Reclaimed water must be identified by purple pipe, warning labels, and signage; it may not be connected to the potable water system except through an approved backflow assembly.

Gray water may be used for subsurface irrigation and toilet flushing where approved; storage and treatment requirements vary by jurisdiction.

Indirect waste receptors must be accessible, located in a ventilated space, and sized to receive full discharge without splash or overflow.

Air gap separation is the only method permitted for indirect waste from a potable water connection; an air gap is a physical separation not subject to back siphonage.

Gas piping must be sized so that pressure loss does not exceed the code allowance; typical natural gas systems use 0.5 inch water column pressure drop in low-pressure systems.

Pipe sizing uses the longest length method or the branch length method with tables based on gas type, specific gravity, and inlet pressure.

Gas pipe must be supported at intervals (typically 6 feet for 1/2 inch and 1 inch, 8 feet for larger sizes) and protected from physical damage.

A pressure test is required before use: 10 psi for 30 minutes or 3 psi for 30 minutes depending on system pressure; test medium is air, not gas.

Shutoff valves must be installed at each appliance and at the manifold; a union or appliance connector is required at each appliance.

Appliance connectors must be listed, of the correct length, and not concealed; they cannot pass through walls, floors, or ceilings.

Sediment traps are required at the inlet of each appliance to catch debris, installed as a tee with a capped nipple.

Combustion air and venting: appliances require adequate combustion air, and flue connections must be listed and terminate per manufacturer and code clearance requirements.

Drainage fixture units are summed per branch and stack; convert to pipe size with the drainage sizing table, checking both horizontal branch and stack capacity.

Slope calculation: fall = length × slope; for a 60-foot run at 1/4 inch per foot, fall = 15 inches.

Volume of a pipe in gallons = 0.0408 × diameter squared (inches) × length (feet); useful for sizing expansion tanks and water heater systems.

Flow rate from fixture units uses demand curves; 1 FU = 1 gpm in supply terms, but the curve flattens at higher FU totals.

Roof drainage: cubic feet per second = rainfall intensity (in/hr) × area (sq ft) / 96; then convert to gallons per minute by multiplying by 448.8.

Plan reading: plumbing plans use symbols for water (solid or dashed lines), drainage (solid), vents (dashed), and risers; match symbols to the legend.

Scale reading: use the stated scale (e.g., 1/4 inch = 1 foot) to convert measured plan distance to actual length before sizing.

Water heater sizing: first-hour rating must equal or exceed peak hourly demand; recovery rate = input BTU/hr ÷ (8.33 × temperature rise).