HBA

Home Builders Association

HD

Head

HP

Horsepower

HT

Hose Threads. Note: Garden hose threads are different from standard pipe threads.

HVAC

Heating, Ventilation, and Air Conditioning.

Hand-shower

A showerhead designed with a handle that's connected to a water supply and a flexible hose.

Hanger

A device used to support pipes.

Hard Water

Natural water containing impurities in various proportions. Traditional hardness is a measure of calcium or dissolved solids in a solution, measured in parts per million. Hard water generally ranges from 100 to 250 ppm.

Hardness

The amount of dissolved minerals in water measured in grains per gallon (GPG). The most common minerals are calcium and magnesium.

Hardness Leakage

The presence of a consistent concentration of hardness in the effluent from an ion exchange water softener, often due to high concentrations of hardness or sodium in the water being treated (see Leakage)

Head

The pressure of water (or steam) in a closed system (see Pressure Head.) It represents the differential in the gravitational force exerted by a liquid at two different depths.

Head Loss

The pressure of water as measured at a stated point, either in feet or in pounds per square inch (PSI).

Heat Exchanger

A heat transfer system.

Heat Sensors

Heat-triggered devices on sprinkler systems that release the flow of water.

Heat Trap

Restriction of heat loss through water connections to a tank.

Hermetic

Completely sealed, especially against the escape or entry of air.

Hold Down

A type of pipe anchor consisting of a U-strap bolted at either end onto a horizontal plate.

Hollow-jet Valve

A valve having a closing member that moves upstream to shut off the flow. The hollow-jet valve discharges a hollow or annular jet dispersed over a wide area.

Horizontal Branch

Lateral drain pipes that run from plumbing fixtures to the waste stack in a building or in the soil.

Horizontal Run

The horizontal distance between the point where fluid enters a pipe and the point at which it leaves.

Hose Bibb

An outdoor faucet, also used to supply washing machines.

House Trap

U-shaped fitting with two adjacent cleanout plugs visible at floor level if main drain runs under floor.

Hub & Spigot Piping

Gravity rated DWV or pressure pipe that has a bell-shaped section at one end and a straight section at the other. As lengths are assembled, the straight end of one fits into the bell of the next.

Hydration

The chemical absorption of water into a substance.

Hydraulic Pressure

Pressure that exists in a system containing non-compressible liquid.

Hydrolysis

The reaction of a salt with water to form an acid and a base.

Hydronic

System of forced hot water.

Hydrojet

Cold inlet tube designed to reduce sediment build-up and increase efficiency in a water heater.

Hydro Jetting (Service)

The process of clearing blocked pipes using high pressure water as a boring and flushing mechanism.

Hydrostatic Pressure

Pressure exerted by or existing within a liquid at rest with respect to adjacent bodies

Hydrostatic Test

Test using non-compressible liquid under pressure at a level equal to or greater than the maximum pressure that will be utilized when in use, such as in steam boilers.

Hypochlorite

The OCL anion; calcium and sodium hypochlorite are commonly used as bleaches and disinfecting agents.