useful GLOSSARY

air gap: a vertical space between a water or drain line and the

flood level of a receptacle used to prevent backflow or

siphonage from the receptacle in the event of negative

pressure or vacuum.

aquifer: an underground waterway that is replenished by

precipitation.

backflow: flow of water in a pipe or water line in a direction

opposite to normal flow.

backflow preventer: a device or system installed in a water

line to stop backflow from a nonpotable source.

blackwater: the wastewater from toilets

and kitchen sinks.

buffer: to shift pH to a specific value.

building footprint: the area of a building on the ground.

cistern: an above or below ground tank used to store water,

generally made of galvanized metal, fiberglass, ferrocement

or concrete.

disinfection: a process in which pathogenic (disease producing)

bacteria are killed by use of chlorine or physical processes.

diverter: a mechanism designed to divert the first flush

rainwater from entering the cistern.

erosion: the loss of topsoil that occurs as a result of run-off.

filtration: the process of separating particles of 2 microns or

larger in diameter from water by means of a porous substance

such as a permeable fabric or layers of inert material housed in

a media filter or removable cartridge filter.

first flush: generally the first 10 gallons of rainwater per 1,000

square feet of roof surface that is diverted due to potential for

contamination.

flow rate: the quantity of water which passes a given point in

a specified unit of time, expressed in gallons per minute.

forcebreaker: an extension of the fill pipe to a point 1” above

the bottom of the cistern, which dissipates the pressure of

incoming rainwater and thus minimizes the stirring of settled

solids.

greywater: the wastewater from residential

appliances or fixtures except toilets and kitchen sinks.

groundwater: water found below ground that has seeped

there through spaces in soil and geologic formations.

hardness: a characteristic of groundwater due to the presence

of dissolved calcium and magnesium which is responsible for

most scale formation in pipes and water heaters.

hydrologic cycle: the continual exchange of water from the

atmosphere to the land and oceans and back again.

leaf screen: a mesh installed over gutters and entry points to

downspouts to prevent leaves and other debris from clogging

the flow of rainwater.

micron: a linear measure equal to one millionth of a meter,

or .00003937 inch.

nonpotable water: water intended for non-human consumption

purposes, such as irrigation, toilet flushing, and

dishwashing.

pH: a logarithmic scale of values of 0 to 14 that measure of

hydrogen ion concentration in water which determines

whether the water is neutral (pH 7), acidic(pH 0-7) or basic

(pH 7-14).

pathogen: an organism which may cause disease.

potable water: water which is suitable and safe for human

consumption.

pressure tank: a component of a plumbing system that

provides the constant level of water pressure necessary for the

proper operation of plumbing fixtures and appliances.

rainwater harvesting: the principle of collecting and using

precipitation from a catchment surface.

roof washer: a device used to divert the first flush rainwater

from entering a cistern.

run-off farming: the agricultural application of harvested

rainwater involving a system of terraces that directs the

rainwater from higher to lower elevations.

sedimentation: the process in which solid suspended particles

settle out (sink to the bottom ) of water, frequently after

the particles have coagulated.

total dissolved solids: a measure of the mineral content of

water supplies.

xeriscape: a landscape practice which specifies regionallyadapted,

drought-resistant plants and other water-conserving

techniques.