A permanently installed device that can be gripped by a bather for the purpose of resting and/or steadying him/herself. Is not limited to but may be located within or without the pool, spa or hot tub or as part of a set of steps or deck-installed equipment.
HARDNESS
The amount of calcium and magnesium in the water in grains per gallon, (expressed as calcium carbonate). This level is important to control during distillation or reverse osmosis processes to prevent scaling. Each grain is equal to 17.1 ppm of calcium and magnesium (expressed as calcium carbonate). What constitutes truly "hard" water is subject to much debate and controversy. Proponents of water softening systems tend to call water "hard" which contains between 3 and 10 grains of hardness. This definition is supported by the American Society of Agricultural Engineers and the Water Quality Association, major supporters of the water softening industry. Water with 10 grains of hardness, is regularly used by consumers, with little or no adverse affect on plumbing or other household functions. Water, which approaches 15 to 20 grains is more in line with situations which require water softening or conditioning. Water with 3 grains of hardness and is termed "moderately hard" by these organizations is typically found in surface and spring water sources, far removed from what one would consider hard water sources.
HEAD
A term used to define water pressure in vertical feet. Or a term representing the energy content of a liquid, expressed as the height of an equivalent vertical column of water. a. This is expressed in feet of head. b. This can apply to both sides of a pump; the suction side and discharge side. c. It is also used to express the total losses in a pumping system (Total Dynamic Head).
HEAVY METALS
Metals having a high density or specific gravity. A generic term used to classify contaminants such as cadmium, lead and mercury. These contaminants can damage living things even at low concentrations and tend to accumulate in the food chain.
HERMETIC
Completely sealed, especially against the escape or entry of air.
HI-RATE PERMANENT MEDIA FILTER
A filter using high velocity
HOMOGENEOUS MEMBRANES
See membranes.
HORIZONTAL RUN
The horizontal distance between the point where fluid enters a pipe and the point at which it leaves.
HOSE CONNECTOR
The fitting used to connect the hose to the vacuum wall fitting (usually a combination hose sleeve and nut).
HOT TUB
A spa constructed of wood with sides and bottom formed separately; and the whole shapes to join together by pressure from the surrounding hoops, bands or rods; as distinct from spa units formed from plastic, concrete, metal or other materials.
HYDRAULIC SHOCK
A damaging condition that occurs when a column of liquid changes direction quickly and increases in velocity. Weakest point in system will break. Causes can be sudden loss of power to the driver, valve closing too quickly, valve closing too slowly allowing backflow.
HYDROGEN SULFIDE
A toxic gas that is detectable by a strong "rotten egg" odor. Associated with high levels of bacterial decay. Commonly found together with iron and manganese contaminants.
HYDROJETS
A fitting that bleeds air and water creating a high velocity, turbulent stream of air enriched water.
HYDROLOGIC CYCLE
The term used to describe how water travels through the environment by evaporation, condensation and precipitation. Identical process is observed in steam distillation systems.
HYDROLYSIS
A chemical process resulting from reactions with water; frequently used in reference to the breakdown of polymers.
HYDROPHILIC
Pertaining to a substance, which readily absorbs water ("water-loving").
HYDROPHOBIC
Pertaining to a substance, which does not readily absorb water ("water-hating").
HYDROTHERAPY INLET FITTING
A special high velocity air entraining inlet fitting to produce a massage effect.
HYDROTHERAPY SPA OR HOT TUB
A unit that may have a therapeutic use which is not drained, cleaned or refilled for each individual. It may include, but not be limited to, hydrojet circulation, hot water and cold water mineral baths, air induction bubbles or any combination thereof. Industry terminology for a spa includes, but is not limited to, “therapeutic pool,” “hydrotherapy pool,” “whirlpool,” “hot spa,” etc.
HYPOCHLORINATOR
A device used to feed, control and measure a solution of sodium or calcium hypochlorite into a water being treated. There are three general types: The positive displacement type which is usually a motor driven unit, the aspirator type actuated by a pressure differential created within the hydraulic system, and the metering type connected to the pump suction using an orifice which is opened and closed by a timing mechanism.
HYPOCHLORITE
A chemical compound commonly found in two forms for use with pools, spas and hot tubs: calcium hypochlorite is a chlorine carrier in both granular and solid form normally containing 70% to 80% available chlorine by weight; sodium hypochlorite is a liquid chlorine carrier normally containing 5% to 16% available chlorine by weight.
HYPOCHLORITE, CALCIUM
A compound of chlorine and calcium used in powder or granulated form usually containing 70% to 80% available chlorine by weight which is released in water solution to act as a germicide or algaecide.
HYPOCHLORITE, SODIUM
A compound usually containing 5% to 16%, or more, available chlorine by weight, in a caustic soda solution, which releases chlorine when added to pool water.