ASSE 5150 key terms

The unobstructed vertical distance through free atmosphere between the lowest opening of a water supply outlet and the flood-level rim of the receiving fixture or vessel. It is the strongest form of backflow protection.

The unwanted reversal of normal flow direction in a piping system, caused by backpressure or backsiphonage, which can draw contaminated water into a potable supply. Prevention devices and assemblies are required wherever a hazard exists.

Backflow produced by a negative or reduced pressure in the supply piping, which pulls nonpotable fluid into the potable system through an unprotected connection. It commonly occurs during main breaks or high-demand events.

Any actual or potential physical link between a potable water system and a source of contamination or pollution. Such connections must be eliminated or isolated by an approved backflow prevention method.

A testable backflow preventer with two independently acting check valves and a hydraulically operated differential relief valve between them. It protects against both backpressure and backsiphonage at high hazard levels and must be tested annually.

A testable assembly of two independently acting, internally loaded check valves with shutoff valves and test cocks. It protects against backpressure and backsiphonage for low-hazard, non-health conditions only.

A backflow device with an air inlet that opens to atmosphere when supply pressure drops, breaking a siphon. It must be installed above the highest downstream outlet and cannot be used under continuous pressure.

The edge of the receptacle from which water would overflow if the fixture's drain were blocked. It establishes the reference elevation for air gaps and vacuum breaker placement.

A drain-line arrangement in which a pipe discharges into a receptor through an air space, preventing sewage backup from entering the fixture or appliance. It differs from an air gap because the drain is not potable supply.

The vertical depth of water held in a trap that blocks sewer gas from entering a building. Code sets minimum and maximum depths, and the seal must remain intact under normal use.

A U-shaped fitting that retains a water seal and connects a fixture outlet to the drainage system. It must be self-cleaning and installed with a uniform, level seal depth.

The pipe segment between a trap weir and the vent connection or stack fitting. Its developed length and slope are limited by code to keep the trap self-cleaning and prevent siphonage.

A vertical pipe that provides air to a drainage system and relieves pressure so trap seals are not siphoned or blown out. It extends above the roof and may serve one or more fixture groups.

The extension of a soil or waste stack above the highest horizontal drain connected to it, terminating outdoors. It vents the stack itself and is distinct from a separate vent stack.

A vent that connects to two or more fixture drains and relieves pressure in a horizontal branch, allowing a row of fixtures to share one vent. It requires specific sizing and installation conditions.

A single vent serving two fixture traps, usually installed between two fixtures on opposite sides of a partition. Its sizing and length limits depend on the fixture drain sizes it serves.

A vertical drainage pipe that carries the discharge of water closets and may also receive other fixtures. It conveys sewage downward and must connect to an approved venting arrangement.

A vertical drainage pipe that carries wastewater from fixtures other than water closets. It must be vented and sized according to the fixture units it serves.

The lowest horizontal piping of a drainage system that receives soil and waste from inside the building and conveys it to the building sewer. It ends at the building wall.

The pipe carrying sewage from the building drain to the public sewer or private disposal system. It begins outside the building wall and is often subject to local jurisdiction requirements.

A dimensionless measure of the probable load a fixture places on the drainage or water supply system. Fixture unit tables convert fixture counts into required pipe sizes.

A value expressing the probable demand a fixture places on the water distribution system, accounting for flow rate and frequency of use. Total values determine the required supply pipe size.

The total measured length of pipe along its centerline, including all fittings and bends converted to equivalent lengths. It is used with friction loss to size supply and drainage piping.

The pressure exerted by water at rest in a piping system, measured in psi or kPa. It must be sufficient at the highest fixture but limited to avoid damaging fixtures and fittings.

The pressure remaining in a water supply system while water is flowing at a given rate. It reflects friction losses and is used to verify adequate fixture flow at remote outlets.

A device that lowers incoming water pressure to a safe, code-compliant level for downstream piping and fixtures. It is required when supply pressure exceeds the code limit and may need a bypass or relief provision.

The increase in water volume as it is heated, which raises pressure in a closed plumbing system. An expansion tank or relief device is needed to control the resulting pressure rise.

A device with a trapped air chamber or piston that absorbs the pressure surge created when flow stops suddenly. It protects piping, valves, and fixtures from noise and damage.

An appliance that heats and stores or delivers potable hot water for domestic use. It requires a temperature and pressure relief valve, proper venting, and clearance from combustibles.

A safety device on a water heater that opens to discharge excess pressure or temperature before the tank fails. Its discharge must terminate safely and must not be capped or reduced.

The air supplied to fuel-burning appliances for complete combustion and safe venting of flue gases. Its quantity and source are regulated and may require outdoor openings or mechanical supply.

A passage or duct that conveys products of combustion from an appliance to the outdoors. It must be sized, sloped, and terminated in accordance with code to prevent spillage of combustion gases.

An accessible opening with a removable cap that allows the drainage system to be cleared of blockages. Required locations and spacing depend on pipe size and length of run.

The fall of a drainage pipe expressed as a ratio or percentage, needed to move waste by gravity without leaving solids behind. Minimum and maximum slopes vary with pipe size.

The pipe from the trap of a fixture to the point where it connects to another drain or vent. Its size and slope are governed by the fixture's load and the venting arrangement.

A receptacle that receives liquid waste indirectly through an air gap or air break rather than a direct connection. It protects the potable supply and drainage system from contamination.

The pre-permit evaluation of construction documents by the authority having jurisdiction to confirm compliance with code before work begins. It commonly results in written comments or approval.

The organization or official responsible for enforcing code requirements, approving materials, and issuing permits. Their interpretations and approvals govern acceptance of installations.

Written authorization from the code authority to perform regulated plumbing or mechanical work. Work must comply with approved plans and be inspected before concealment or use.

A required inspection of piping and connections performed after installation but before walls, floors, or ceilings are closed. It verifies materials, sizing, slope, and venting before concealment.

The last inspection of completed work, confirming that fixtures, appliances, and systems operate properly and match approved plans. Approval precedes occupancy or use of the system.

A pressure test that fills a system with water to verify joints and piping are leak-free. It is commonly used for drainage and water supply piping before final acceptance.