IAPMO PPE cheat sheet

The Uniform Plumbing Code (UPC) is the model code most associated with IAPMO; local amendments adopted by the authority having jurisdiction (AHJ) supersede model text.

The code establishes minimum requirements for health, safety, and welfare; where the code is silent, the AHJ interprets, and approved manufacturer instructions govern installation.

Permits are required before installation, alteration, or repair of plumbing systems; work exempt from permits is defined in the administrative chapter of the code.

Fixtures must be listed and installed per their listing; a fixture not listed or labeled by an approved agency is not acceptable for code compliance.

Code provisions apply at time of installation; existing installations legally in place are generally not required to be upgraded unless the code or AHJ requires it.

Clearances: water heaters, fixtures, and appliances require accessible service space per code and manufacturer listing; access must not be obstructed by permanent construction.

Inspection stages typically include rough-in (before concealment), drain/waste/vent testing, water supply testing, and final inspection after fixtures are set.

Code adoption structure: model code plus local amendments; the edition year in force is the one adopted by the jurisdiction, not necessarily the newest published edition.

Fixture unit (FU) values convert fixture counts to design flow: 1 FU ≈ 1 gpm of demand for supply sizing; drainage FU values differ from supply FU values.

Drainage slope: 2-inch and smaller pipe at 1/4 inch per foot; 3-inch at 1/8 inch per foot minimum; larger pipe may use 1/8 inch per foot where approved.

Vent stack sizing depends on drainage fixture units connected and stack length; each trap requires a vent sized per the drainage pipe it serves.

Trap arm length limit: distance from trap weir to vent connection is limited by pipe diameter (commonly 5 ft for 1-1/2 inch, longer for larger sizes per code table).

Water closet setting: closet flange must be secured to floor and drain; rough-in dimension measured from finished wall to center of flange (commonly 12 inches).

Horizontal drainage piping changes in direction greater than 45 degrees require a wye or combination fitting; sanitary tees are limited to vertical-to-horizontal flow.

Water heater installation requires a temperature and pressure relief valve piped full size to a safe discharge point, with no traps or reductions and gravity drainage.

Expansion: thermal expansion control is required in closed water systems; a thermal expansion tank or equivalent device protects the system from overpressure.

Minimum residual pressure: typically 8 psi at fixtures during peak demand (code minimum), with 15-20 psi commonly used for design at the building supply.

Static vs. residual pressure: static pressure is measured with no flow; residual is measured while flowing, and friction loss is the difference between them.

Water service sizing uses total supply fixture units converted to probable demand (gpm) via code tables, then pipe sized for allowable velocity and friction loss.

Velocity limits: cold water typically limited to about 8 fps and hot water to about 5 fps to control noise, erosion, and water hammer.

Drainage fixture units are assigned per fixture type and combined for the building drain; the building drain must be sized for the total DFU plus slope.

Storm drainage is sized separately from sanitary drainage; roof drain sizing uses rainfall intensity (inches per hour) and roof area.

Water hammer arrestors are required where quick-closing valves are installed; they are placed near the fixture or valve causing the surge.

Backwater valves are required where fixtures are below the elevation of the next upstream manhole or where the building drain can be subject to backflow from the public sewer.

Cross-connection: any actual or potential connection between potable water and a source of contamination or pollution; must be eliminated or protected by an approved assembly.

Air gap is the only absolute backflow protection; minimum air gap is typically twice the effective opening of the supply pipe, with a code minimum of 1 inch.

Backflow causes: backsiphonage (negative pressure in supply) and backpressure (downstream pressure exceeds supply pressure).

RPZ (reduced pressure zone) assembly protects against both backsiphonage and backpressure at high hazard; test cocks and shutoff valves are integral.

Double check valve assembly protects against backpressure and backsiphonage at low hazard only; not acceptable for high-hazard connections.

Pressure vacuum breaker (PVB) protects against backsiphonage only and must be installed at least 12 inches above the highest downstream outlet.

Atmospheric vacuum breaker (AVB) protects against backsiphonage only, must be installed 6 inches above the highest downstream point, and cannot be under continuous pressure.

Test requirements: reduced pressure assemblies and double check assemblies require annual testing by a certified tester, with results filed with the water authority.