The flow pattern in which water flows from the outside of a filter element to the center core. For example, a replaceable particulate or carbon cartridge filter unit.
RATE OF FLOW (GPM)
The measurement of the volume of flow per unit of time expressed in gallons per minute.
RATE OF FLOW INDICATOR
A device to indicate the rate of flow in a pipe line (sometimes referred to as a “rate-of-flow meter”).
RATED PRESSURE
That pressure that is equal to or less than the designed pressure and appears on the dataplate of the equipment.
RECIRCULATING SYSTEM
The entire system including the suction piping, pump, strainer, filter, face piping and return piping.
RECOVERY (PERCENT RECOVERY)
A measurement applied to distillation, reverse osmosis and ultrafiltration equipment, which characterizes the ratio of product water to feed water flow rates. The measurement is descriptive of distillation reverse osmosis or ultrafiltration equipment as a system and not of individual membrane elements. Expressed as a , recovery is defined as: % Recovery = (Product flow rate/Feed flow rate) x 100.
REGENERATION
Carried out using either an acid or alkali to remove the accumulated cations or anions, respectively from a filtration media. At the same time, the cation exchanger takes on hydrogen ions, to restore them to the original hydrogen or hydroxide form, respectively.
REJECTION (PERCENT REJECTION)
A measure of the ability of a reverse osmosis membrane to remove salts. Expressed as a percentage, rejection is defined as: Rejection = (l-Product concentration/Feed concentration) x 100.
REMOVABLE
Capable of being disassembled with the use of only simple tools such as a screwdriver, pliers or wrench.
RESIDUAL
Usually refers to chlorine residual, or the amount of measurable chlorine remaining after treating water with chlorine. Free residual differs from combined residual in that it is not combined with ammonia or other elements or compounds, and is a more effective disinfectant.
RESIN
Specially manufactured polymer beads used in the ion exchange process to remove dissolved salts from water.
RETURN PIPING
That part of the pool, spa or hot tub piping between the filter and the vessel through which filtered water passes.
REVERSE OSMOSIS
A reversal of the natural phenomenon of osmosis brought about by application of hydraulic pressure greater than the osmotic pressure in water (containing dissolved solids) to cause the water molecules to flow through the membrane away from the dissolved substances.
RO
Reverse Osmosis-a method of water treatment.
RYZNAR INDEX
A modification of the Langelier index used to calculate the degree of calcium carbonate saturation and to predict the likelihood of scale formation from a water supply.