MN Plumber key terms

A dimensionless number expressing the probable peak drainage load or water demand of a plumbing fixture, used to size pipes by summing the values of connected fixtures rather than counting fixtures.

The fixture-unit value assigned to a fixture for sizing sanitary drainage piping, reflecting its discharge rate and waste characteristics; a water closet is typically 3 DFU and a lavatory 1 DFU.

The fixture-unit value assigned to a fixture for sizing water distribution piping, based on its flow rate and the probability of simultaneous use among fixtures on the system.

A probability-based chart relating total water supply fixture units to probable peak demand in gallons per minute, forming the basis for sizing water service and distribution mains.

An unobstructed vertical distance through open air between a potable water outlet and the flood-level rim of a receptor, providing the highest degree of backflow protection against both backpressure and backsiphonage.

A drain arrangement where a pipe discharges into a receptor through an air space rather than a true air gap, used to prevent sewage backup from contacting fixtures or equipment indirectly connected to the drainage system.

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

An approved assembly such as a reduced-pressure-zone device or double check valve that stops reverse flow of water into the potable supply caused by backsiphonage or backpressure.

A testable backflow assembly with two independently acting check valves separated by a hydraulically operated differential relief valve, giving protection against both backsiphonage and backpressure.

A device that admits air into a pipe to break a vacuum and prevent backsiphonage; the atmospheric type must be installed on the discharge side of the last control valve and cannot be used under continuous pressure.

The top edge of a fixture or receptor from which water would overflow onto the floor, establishing the reference elevation for setting air gaps and fixture outlet heights.

The lowest point in a fixture drain where water exits the fixture, used as the reference for trap arm length limits and the vertical distance to the trap weir.

The crown of the waterway in a trap, at the point where the outlet pipe begins to slope downward; its elevation relative to the fixture outlet governs whether a trap is over-set.

The depth of water retained in a trap between the weir and the dip of the trap, normally 2 to 4 inches, which blocks sewer gas from entering the building.

The portion of pipe between the trap weir and the vent connection; its length and slope are limited so that the trap is not self-siphoned by the discharge of the fixture.

A U-shaped trap with a swivel or union connection that retains a water seal and discharges horizontally through an arm to a drain; it is the standard trap for fixtures without an integral trap.

A vertical pipe installed to provide circulation of air to and from the drainage system, extending from a soil or waste stack above the highest fixture connection to open air above the roof.

The extension of a soil or waste stack above the highest horizontal drain connected to it, serving as the vent for that stack and terminating outdoors above the roof.

A vertical drainage pipe that carries the discharge of water closets and may also receive other fixture wastes; it must be vented and sized according to the fixtures it serves.

A vertical drainage pipe that carries liquid waste from fixtures other than water closets, such as sinks and lavatories, and is vented to protect trap seals.

A vertical section of a stack equal in height to one story, used to limit the number of fixture units that may connect to a stack of a given size and to determine vent sizing.

A vent connecting two or more fixture drains to a common vent that serves as the vent for a battery of fixtures, allowing a single vent to protect multiple traps.

A vent installed to provide additional air between a vent stack and a soil or waste stack, preventing pressure differences that could siphon fixture traps in tall drainage systems.

An accessible opening with a removable plug or cover installed in drainage piping to allow clearing of blockages; required at the base of stacks, at changes in direction, and at intervals along horizontal runs.

The lowest piping of a drainage system that receives the discharge of soil, waste, and other drains inside the building and conveys it to the building sewer, ending at the building wall.

The pipe carrying sewage from the building drain to the public sewer or private disposal system, beginning outside the building wall and typically owned by the property owner.

A trap installed in the building sewer near the foundation that separates the building drainage system from the public sewer; many codes now prohibit it except where required by the authority having jurisdiction.

The system of roof drains, leaders, area drains, and storm sewers that conveys rainwater and surface water away from a building, kept separate from the sanitary drainage system.

A fitting installed at the low point of a flat roof that collects rainwater and directs it into a leader; its size and number depend on roof area and local rainfall intensity.

A vertical pipe that conducts rainwater from a roof drain or gutter to a storm drain or approved point of disposal; it must not be used to carry sanitary waste.

Devices such as grease traps, sand traps, or oil separators installed in drainage lines to capture fats, oils, grease, or solids before waste enters the sewer, protecting the system from clogging.

An interceptor that separates fats, oils, and grease from kitchen wastewater by flotation, retaining the grease while allowing clarified water to flow to the drainage system.

A receptacle that receives liquid waste from fixtures or equipment through an air break or air gap and discharges to the drainage system, used for food-service equipment and similar fixtures.

A pump installed in a sump pit to remove accumulated water from basements, crawl spaces, or storm drainage systems, discharging to an approved point such as a storm drain or exterior grade.

A one-way valve installed in a drainage line to prevent sewage from backing up into a building during surcharge of the public sewer; it must be accessible for maintenance.

A pressure surge caused by the sudden stopping of water flow, producing a banging noise and potential pipe damage; controlled by air chambers, water hammer arrestors, or slow-closing valves.

A device containing a trapped air cushion or piston that absorbs the shock wave created when water flow stops abruptly, protecting piping and fixtures from pressure spikes.

A valve that reduces incoming water pressure to a safe, usable level for the building distribution system, typically installed where street pressure exceeds the code maximum.

The increase in water volume as it is heated in a closed system, which can raise pressure and require a thermal expansion tank or relief valve to prevent damage.

An appliance that heats potable water for domestic use, requiring a temperature and pressure relief valve, a safe discharge pipe, and proper venting when fuel-fired.

A safety device on a water heater that opens to release water if temperature or pressure exceeds safe limits, with its discharge piped to an approved drainage point.

The passage or pipe that carries combustion products from a fuel-burning appliance to the outdoors, sized and installed to maintain proper draft and prevent spillage of gases.

A device on a gas appliance that admits dilution air and stabilizes draft, preventing downdrafts and ensuring combustion gases are safely vented.

The system of pipes, fittings, and valves that conveys fuel gas from the meter or supply source to appliances, sized by load and length and tested for leaks before being placed in service.

A short vertical leg installed at the appliance connection to catch dirt, scale, and condensate before they reach the gas controls, required on most gas appliances.

A vertical extension of gas piping at an appliance connection that collects condensate and debris; often used interchangeably with sediment trap in common practice.

A manually operated shutoff valve installed in gas piping near an appliance so the gas supply can be isolated for service or emergency; must be accessible and clearly identified.

A three-dimensional representation of piping in which vertical, horizontal, and depth lines are drawn at fixed angles, used to plan and lay out drainage and supply systems.

A schematic drawing showing the vertical arrangement of piping, fixtures, and vents in a building, with stacks and floors depicted to clarify drainage and venting relationships.

A drawing that shows a building layout as seen from above, indicating fixture locations, pipe routes, and dimensions used for material takeoffs and installation layout.

The total length of pipe measured along its centerline including all fittings and changes in direction, used for material takeoffs and for sizing gas and water piping.

The friction loss of a fitting or valve expressed as a length of straight pipe that would produce the same pressure drop, added to actual pipe length when sizing systems.

The pipe connecting a fixture or group of fixtures to a soil, waste, or vent stack, sized by the fixture units it carries and limited in length by venting requirements.

The fall of a horizontal drainage pipe expressed as inches per foot, commonly one-quarter inch per foot for small pipe, ensuring gravity flow and scouring velocity.

A fixture that receives human waste and discharges it through an integral trap into the drainage system; its flush volume and connection size are regulated by code.

The legal authorization granted by a state or local board to perform plumbing work, requiring documented experience, examination, and continuing education for renewal.

An official document issued by the authority having jurisdiction authorizing specific plumbing work, subject to plan review, inspection, and compliance with adopted codes.

The organization, office, or individual responsible for enforcing code requirements, approving materials and methods, and conducting inspections of plumbing installations.

The pressure drop caused by water flowing through pipe and fittings, increasing with flow rate, pipe length, and roughness; it must be accounted for when sizing distribution systems.