MPLE Board Exam key terms

A dimensionless measure of the probable load a plumbing fixture places on the drainage or water supply system, based on its flow rate and pattern of use, used to size pipes rather than counting fixtures alone.

The load value assigned to a fixture for drain, waste, and vent sizing, reflecting the fixture's discharge rate and drain outlet size; used to determine required drain pipe diameters and branch sizes.

A load rating assigned to fixtures for sizing water distribution piping, derived from fixture flow demand and diversity of simultaneous use; summed values select supply main and branch sizes.

The estimated peak demand, in liters or gallons per minute, expected from a group of fixtures when not all are used at once; estimated from fixture unit totals to size supply piping economically.

The pipe section between a fixture trap and its connection to a branch or stack, limited in length by code so that the trap seal is not self-siphoned; its slope and length are regulated.

The water held in a fixture trap's U-bend that blocks sewer gas from entering the building; its depth is specified by code and must be maintained against evaporation and siphonage.

A vertical pipe extending above the drainage system that admits air to balance pressure and allows sewer gases to escape outdoors; its size and connection to the drainage stack are code-regulated.

The extension of a soil or waste stack above the highest fixture connection, serving as a vent for the stack; it terminates above the roof so gases discharge outside the building.

A one-way valve that admits air into a drainage system to relieve negative pressure but closes to prevent sewer gas escape; permitted only under stated code conditions and with proper access.

A pipe that carries sewage containing fecal matter from water closets; distinguished from a waste pipe, which carries only liquid waste free of such solids, with different sizing and material rules.

A device or assembly that stops contaminated water from reversing into the potable supply, protecting against back-siphonage and backpressure; selection depends on the degree of hazard.

The unobstructed vertical distance between a potable water outlet and the flood level rim of a receptacle; the simplest and most reliable backflow protection when correctly maintained.

Any actual or potential link between a potable water system and a source of contamination or pollution; it must be eliminated or protected by an approved backflow device.

A device that opens to atmosphere when supply pressure drops, breaking a siphon and preventing back-siphonage; types include atmospheric and pressure-type, each with installation restrictions.

The edge of a fixture or receptacle over which water would overflow onto the floor; used as the reference point for air gap measurement and backflow protection.

A fixture that receives human waste and discharges it through a trap to the drainage system; its flush volume, trapway, and rough-in dimensions are governed by code and efficiency standards.

A drain set in the floor to carry away spilled water and cleaning waste, requiring a trap and usually a backwater valve; common in basements, kitchens, and mechanical rooms.

A valve installed on a drainage line to prevent sewage from reversing into a building during surcharge or flooding of the public sewer; often required on lowest-level fixtures.

The banging or pressure surge caused by sudden stopping of water flow in a pipe; controlled by air chambers, surge arrestors, or slow-closing valves, and prevented by proper pipe support.

A device that lowers incoming water pressure to a safe, usable level for the building's distribution system, protecting fixtures and piping from excessive pressure and reducing noise.

The total measured length of pipe plus equivalent lengths for fittings and valves along a run; used with flow rate to calculate friction loss and required pressure.

The pressure drop caused by water moving through pipe, fittings, and valves; it grows with flow velocity and pipe roughness and must be accounted for when sizing distribution systems.

The pressure created by the vertical height of water above a point, independent of flow; it must be added to or subtracted from supply pressure when checking fixture performance.

The pressure equivalent of the kinetic energy of moving water, expressed as a function of velocity; relevant in system analysis and in understanding pressure changes at fittings.

The downward inclination of a horizontal drain pipe, expressed as a ratio or percentage, that lets waste flow by gravity while carrying solids; code sets minimum and maximum values by pipe size.

The lowest point of the inside of a pipe at a given cross-section; invert elevations are used to set drainage slopes and to align connections between piping runs.

An accessible fitting or opening that allows a drain line to be rodded or jetted to remove blockages; code requires them at specified intervals, changes of direction, and ends of runs.

Hangers, clamps, or brackets that hold piping at code-specified spacing to carry weight, control expansion, and prevent sagging or vibration; spacing depends on pipe material and size.

The lengthening of pipe as water or ambient temperature rises; in closed systems it raises pressure and can damage joints, so expansion loops, tanks, or offsets are provided.

Water that is safe for drinking, cooking, and personal use because it meets health-based quality standards; plumbing systems must protect it from contamination at every connection.

A standardized size label for pipe that approximates but does not exactly equal the actual outside or inside diameter; it guides selection of fittings and code tables.

A wall-thickness classification for pipe, such as Schedule 40 or 80, where a higher number means thicker walls and greater pressure rating for the same nominal size.

A fluid that softens and fuses thermoplastic pipe and fittings, such as PVC or CPVC, into a joint; correct primer, cement type, and cure time are essential for a sound connection.

A fitting that separates dissimilar metals, such as copper and steel, to stop galvanic corrosion at the joint; commonly used where piping materials change.

Deterioration of one metal when it is joined to a different metal in the presence of an electrolyte, driven by the difference in their electrical potentials; avoided by dielectric fittings or compatible materials.

A flexible plastic tubing widely used for hot and cold water distribution, joined by crimp, clamp, or press fittings; it resists corrosion and scale but needs protection from sunlight and freezing.

A heavy, durable drainage material valued for quiet operation and fire resistance; joined by hub-and-spigot, no-hub couplings, or mechanical joints, depending on the type used.

A technical document that sets minimum requirements for materials, design, or installation, often adopted by reference into law; compliance is mandatory once a jurisdiction adopts it.

Official authorization to construct or alter plumbing work, issued after plans are reviewed; work done without one is unlawful and may require removal or penalties.

A required check by the authority having jurisdiction at set stages, such as rough-in and final, to confirm work matches approved plans and code before it is covered or used.

The stage of installation when piping is in place but fixtures and finishes are not yet set; it must be inspected before concealment in walls, floors, or ceilings.

The official or agency responsible for enforcing the plumbing code and approving installations, interpretations, and permits within a given area.

A situation where a professional's personal, financial, or other interest could improperly influence judgment or duty; it must be disclosed and avoided to preserve integrity.

The degree of skill and care that a reasonably competent practitioner in the same field would exercise under similar circumstances; it is the benchmark for negligence claims.