MS Plumber key terms

The official or agency that enforces a plumbing code and has final say on compliance, including approving materials, methods, and interpretations where the code is silent or ambiguous.

A written authorization issued by the AHJ allowing specified plumbing work to proceed; work done without one is typically a violation subject to stop-work orders, fees, or removal.

The AHJ's on-site verification that installed work matches the approved plans and code, commonly required at stages such as rough-in, underground, and final before systems are covered or used.

The stage of plumbing work completed before walls, floors, or fixtures are finished, including installed piping, fittings, and supports that must be inspected before concealment.

A formal or informal written opinion from the AHJ resolving how a code section applies to a specific installation, often requested when a design is unusual or the text is unclear.

A dimensionless number expressing the probable load a fixture places on the drainage or water supply system, based on its flow rate, use frequency, and drain size.

A value assigned to each fixture reflecting its probable discharge into the sanitary drainage system; fixture units are summed to size branches, stacks, and building drains.

A value reflecting the probable demand a fixture places on the water distribution system, accounting for supply flow rate and simultaneous use; used with demand curves to size piping.

The water layer held in a trap's dip that blocks sewer gas from entering a building; its depth is regulated, typically between two and four inches.

A U-shaped fitting that holds a water seal to prevent sewer gas entry while allowing wastewater to pass; it must be self-cleaning and installed level.

The pipe section between a trap's outlet and its connection to a drain or stack; its length and slope are limited to protect the trap seal from siphonage.

A pipe that admits air to the drainage system or releases gas, protecting trap seals from siphonage and allowing smooth flow; every trap must be vented except where exceptions apply.

A vertical vent pipe extending through the roof that serves one or more drainage stacks, equalizing pressure and discharging sewer gas above the building.

A one-way mechanical valve that opens to admit air into a drain line and closes to prevent gas escape, permitted only under specific conditions and locations set by code.

A vertical pipe carrying wastewater or vent air through multiple floors; soil stacks carry sewage and vent stacks handle air, and both require proper support and cleanouts.

The lowest horizontal pipe of the drainage system that receives waste from all interior fixtures and conveys it to the building sewer, usually just inside the foundation wall.

The pipe outside the building that carries wastewater from the building drain to the public sewer, private disposal system, or other point of disposal.

An accessible fitting with a removable cap that allows a drain line to be rodded or inspected; code sets required locations, spacing, and sizing.

The downward pitch of a horizontal drain pipe, expressed as fall per unit length, that keeps solids moving; too little causes clogs and too much can leave liquids behind.

A one-way device installed on a drain to prevent sewage from reversing into a building during surcharge or flooding; required where fixtures are below the upstream manhole.

Any actual or potential link between a potable water supply and a source of contamination or pollution, which must be eliminated or protected by an approved backflow preventer.

The unwanted reversal of water flow in a piping system, caused by backpressure or backsiphonage, that can draw contaminants into the potable supply.

The unobstructed vertical distance between a water supply outlet and the flood-level rim of a receiving fixture; it is the most reliable form of backflow protection.

A testable or non-testable assembly, such as a reduced-pressure zone device or double check valve, installed to stop reverse flow; many types require annual testing by a certified tester.

The top edge of a fixture or receptacle from which water would overflow onto the floor; it sets the height for air gaps and the minimum elevation for certain fixtures.

A receptacle or device that receives water or waste and discharges it to the drainage system, such as a sink, water closet, or tub; each has code-set clearances and connections.

A toilet fixture that receives waste and discharges through a trap; code regulates its flush volume, rough-in dimensions, and clearance from walls and other fixtures.

A safety device that opens to release excess pressure or temperature from a water heater, preventing tank rupture; it must be piped to a safe discharge point.

The increase in water volume as it is heated in a closed system, which raises pressure and can damage components unless absorbed by an expansion tank or relieved by a valve.

A pressure surge caused by a sudden stop in water flow, producing banging and stress on piping; arrested by air chambers, water hammer arrestors, or proper pipe sizing.

The drop in water pressure as water moves through pipe, fittings, and valves due to friction and elevation; it must be calculated to ensure adequate pressure at the farthest fixture.

The total measured length of a pipe run including fittings and offsets, used in sizing and pressure-loss calculations rather than straight-line distance alone.

A code-provided chart that converts fixture units or drainage area into required pipe diameter, accounting for slope, building type, and allowable load.

The system that collects and conveys rainwater and other clear water from roofs, yards, and paved areas to a disposal point, kept separate from sanitary drainage.

A two-part roof system where primary drains handle design rainfall while secondary drains or scuppers provide a backup path when primary drains are blocked or overloaded.

A fitting installed at a roof low point that admits rainwater into the storm system, often with a strainer and a sump to limit debris entry.

The approved technique for connecting pipe and fittings, such as solvent cement, soldering, brazing, press, or threaded joints; each material has code-listed methods and restrictions.

A joining method for plastic pipe where cement softens surfaces so they fuse; requires clean, square cuts, proper primer and cement, and adequate cure time before pressure testing.

A fitting that separates dissimilar metals, such as copper and steel, to break electrical continuity and reduce galvanic corrosion at the joint.

A required check that piping holds specified pressure for a set time without leaks before it is covered or placed in service, often witnessed by the inspector.

The required height and location where a vent stack exits the roof, set to prevent snow blockage and keep gases away from windows, doors, and air intakes.

A safety procedure that isolates energy sources and applies tags and locks so equipment cannot be energized during service, protecting workers from shock, burns, or sudden startup.

A space with limited entry or exit that is not designed for continuous occupancy, such as a vault or pit; entry may require testing, ventilation, an attendant, and a permit.

Gear worn to reduce injury risk, including eye protection, gloves, respirators, and hearing protection, selected for the hazards present at the jobsite.