IAPMO UPC PI cheat sheet

The Uniform Plumbing Code is published by IAPMO and is adopted by reference through state or local ordinance; the code edition in force is the edition adopted by the authority having jurisdiction (AHJ), not necessarily the newest printing.

Permit required: new plumbing installation, alteration, replacement, relocation, or repair of any plumbing system, plus any installation requiring water, waste, or vent connections, generally needs a permit before work begins.

Exempt from permit: minor repair work such as stopping leaks, clearing stoppages, or replacing a faucet washer, and replacement of exposed fixture fittings where no change to the piping system occurs, per the code's permit exemptions.

The AHJ is the officer or agency charged with enforcement; the AHJ interprets code provisions, may approve alternate materials and methods, and may grant modifications when equivalent safety and intent are met.

Alternate materials and methods require written request and approval; the AHJ may require evidence such as test data or listing reports demonstrating equivalence to the prescribed method.

Approved means acceptable to the AHJ; listed means included in a list published by an approved agency concerned with product evaluation; labeled means bearing an approved agency's label.

Plans and specifications must be submitted for systems the AHJ determines are complex; the submittal must show location, size, and type of piping, fixtures, and vents, and be drawn to scale.

Unsafe or unlawful work: the AHJ may order correction, may suspend or revoke a permit, and may require disconnection of water or gas service where an imminent hazard exists.

Definitions that drive application: plumbing system includes water supply, fixtures, drainage, venting, traps, and gas piping within the property line; fixture branch and fixture drain are defined by the fixture they serve.

Fixture clearances: water closets require not less than 15 inches from the centerline of the fixture to any side wall or partition and not less than 30 inches center-to-center between adjacent water closets.

Minimum fixture spacing in front of a water closet or lavatory is 21 inches of clear space from the fixture to any wall, door, or obstruction; showers require a minimum 30-inch by 30-inch finished interior.

Each fixture must be individually trapped except where a single trap serves a set of fixtures as permitted (e.g., a continuous waste from a set of sinks, or a floor drain with a trap), and each trap must have a liquid seal of not less than 2 inches and not more than 4 inches.

Trap arms: the developed length from a trap to its vent may not exceed the limits in the venting table (commonly 3.5 to 5 feet for small traps), and the trap arm must fall at a slope no steeper than one pipe diameter per run to prevent self-siphoning.

Water closet bowls must be of the siphon-jet, blowout, or siphon-vortex type; water closets must be listed and must not exceed 1.6 gallons per flush unless the code edition permits alternate flush volumes.

Fixture units (FU) are the relative load values assigned to fixtures; drainage fixture units for a private lavatory are 1, a water closet is 3 (public 4-6 depending on type), and a residential kitchen sink is 2.

Minimum lavatory size is a nominal 18-inch by 12-inch bowl; sinks and lavatories must be set level and must be provided with an overflow unless the fixture is a type that does not require one.

Drinking fountains must be listed, must have a stream height controlled to avoid mouth contact, and must not be installed in a restroom; floor drains are required in public restrooms, in rooms containing food preparation equipment, and in other locations subject to water discharge.

Indirect waste connections: fixtures such as refrigerators, ice makers, dishwashers, and sterilizers must discharge through an air gap or air break, and the indirect waste pipe must be sized to carry the discharge and trapped where required.

Water supply sizing uses the total demand in water supply fixture units (WSFU) converted to probable peak demand in gallons per minute, then the pipe size is selected from the applicable table for the pressure available and the developed length of the run.

Minimum residual pressure: 8 psi flowing at the fixture farthest from the source for flush-tank water closets, 15 psi for flushometer valves if the code table permits, and 8 psi for other fixtures; the code sets the minimum at the building supply and at fixtures.

Drainage slope: horizontal drainage pipe 2.5 inches and smaller must slope at 1/4 inch per foot; 3-inch and larger pipe may slope at 1/8 inch per foot where the code table permits, and no drainage pipe may slope less than 1/8 inch per foot.

Drainage fixture units to pipe size: a 1.5-inch drain carries up to 3 FU, 2-inch up to 6 FU (with slope limits), 3-inch up to 20 FU, and 4-inch up to 160 FU for horizontal branches; verify against the slope-adjusted table in the code.

Vent sizing: the vent stack must be sized per the vent table; a 1.5-inch vent serves up to 8 drainage fixture units on a branch, 2-inch up to 24 FU, and 3-inch up to 84 FU, with larger sizes required as the stack length and fixture-unit load increase.

Every trap must be vented, and the vent must be taken off the trap arm within the trap-arm length limit; a vent may not be installed downstream of the trap in a way that creates a crown vent, and a vent must rise vertically at least 6 inches above the fixture flood level rim before offsetting.

A common vent may serve two fixture drains at the same level, and a wet vent may serve a limited number of fixtures where the wet-vented pipe is one or two pipe sizes larger than required and the fixture load limits are met.

Cleanouts: a cleanout is required at the base of each vertical waste or soil stack, at the upper end of each horizontal drainage pipe, at each change of direction greater than 45 degrees, and at intervals not exceeding 100 feet in horizontal runs.

Air admittance valves may be used only where the code edition and the AHJ permit, must be listed, must be installed above the fixture flood level rim, and must be accessible; they do not replace a required vent stack to open air.

Gas pipe sizing uses the longest-length method: measure the developed length from the meter to the farthest appliance, sum the connected loads in cubic feet per hour (BTU input divided by the heating value of the gas), and select pipe size from the capacity table for the gas type and pressure.

Natural gas heating value used for sizing is typically 1,000 BTU per cubic foot; for propane, the input is divided by approximately 2,500 BTU per cubic foot, and the tables are specific to gas type and pressure.

Pipe sizing tables differ by pressure regime and material: schedule 40 steel, corrugated stainless steel tubing (CSST), and copper each have separate capacity tables, and CSST must be installed per its listing, including bonding and strike protection.

Sediment trap (drip leg) required at each appliance: a tee with a capped nipple installed downstream of the appliance shutoff valve, with the nipple extending downward at least 3 inches, arranged so debris does not enter the appliance controls.

Appliance connectors: a listed flexible connector may not exceed 6 feet in length (longer lengths are permitted only where the listing allows for specific appliances such as ranges), must not pass through a wall, floor, or ceiling, and must not be concealed.

Shutoff valve required in the same room and within 6 feet of the appliance, and a union or ground-joint connection must be provided at the appliance for removal; the valve must be of a type listed for gas service.

Combustion air: appliances must have combustion and dilution air per the code and manufacturer's instructions; a confined space requires two permanent openings, one near the top and one near the bottom, sized per the volume and BTU input.

Venting of gas appliances: a category I appliance vents into a listed vent or chimney with proper rise and termination; vent connectors must slope upward toward the chimney, and clearances to combustibles must match the listing.

Bonding: gas piping must be bonded to the grounding electrode system where the code or the local electrical code requires it, and CSST requires bonding per the manufacturer's instructions, typically with a minimum 6 AWG conductor.

Rough-in inspection occurs after all piping is installed and before it is covered; the inspector verifies pipe size, slope, venting, support spacing, and trap installation before concealment.

Drainage and vent system test: the system is filled with water to a point not less than 10 feet above the highest point of the section under test (or the highest point of the system if lower) and held for at least 15 minutes without leakage, or tested with air at not less than 5 psi for 15 minutes.

Water supply system test: the system is filled with water and tested at a pressure of not less than the working pressure under which it will be used, with a minimum of 100 psi for at least 60 minutes, or tested with air where permitted by the AHJ.

Final inspection occurs after fixtures are set, traps are primed, and the system is complete; the inspector verifies fixture clearances, backflow protection, gas appliance connections, and labeling of shutoffs.

Plan review checklist: confirm occupancy and fixture count against the minimum fixture requirements table, verify pipe sizing calculations, check vent and drain slopes, confirm backflow prevention devices, and verify gas load calculations.

Minimum fixtures required are based on occupancy classification; for example, an assembly occupancy requires water closets and lavatories at ratios set by the table and by occupant load, and employee facilities must be provided for each sex where required.

Backflow protection: an air gap is the preferred method; reduced-pressure principle backflow assemblies are required where a health hazard exists, and double check valves where a non-health hazard exists; assemblies must be tested and tagged at installation and annually.

Records and approvals: the AHJ must be notified before covering work, and the approved plans must be kept on site; deviations from approved plans require a revised submittal and re-approval before installation.

Deficiency correction: the inspector issues a correction notice listing code sections; reinspection is required after correction, and the permit may be suspended if work proceeds without required inspections.

A permit is required before installing, altering, or replacing plumbing, but not for minor repairs like clearing stoppages or replacing a faucet washer.

Alternate materials need written AHJ approval supported by listing or test data showing equivalence to code intent.

Plans drawn to scale must show pipe sizes, fixture locations, and vent routing when the AHJ requires submittal.

The AHJ may suspend or revoke a permit for unsafe work or for work that deviates from approved plans.

Water closet centerline to side wall: minimum 15 inches.

Water closet center-to-center spacing: minimum 30 inches.

Clear space in front of a water closet or lavatory: minimum 21 inches.

Shower interior minimum: 30 inches by 30 inches finished.

Each fixture is individually trapped unless the code permits a shared trap arrangement.

Trap seal depth: minimum 2 inches, maximum 4 inches.

2.5-inch and smaller horizontal drains: slope 1/4 inch per foot; 3-inch and larger may use 1/8 inch per foot.

Cleanout required at the base of each stack and at the upper end of each horizontal drain.

Vent must rise at least 6 inches above the fixture flood level rim before offsetting.

Trap arm length is limited by the vent table and must not exceed the developed length allowed for its size.

Developed length is measured from the meter to the farthest appliance, using the longest run, not the sum of all runs.

Connected load in cubic feet per hour equals appliance BTU input divided by the gas heating value (about 1,000 BTU per cubic foot for natural gas).

Sediment trap: tee with capped nipple at least 3 inches long, installed downstream of the appliance shutoff.

Appliance connector maximum length is 6 feet unless the listing permits longer, and it may not pass through a wall or be concealed.

Shutoff valve must be in the same room and within 6 feet of the appliance.

Drainage and vent water test: fill to at least 10 feet above the highest point of the section under test, hold 15 minutes with no leakage.

Drainage and vent air test: minimum 5 psi held for 15 minutes where permitted.

Water supply test: minimum 100 psi or the working pressure, held for at least 60 minutes.

Rough-in inspection must occur before piping is covered or concealed.

Backflow assemblies must be tested at installation and annually thereafter, with tags documenting the test.