The manufacturer's specified range of pressure expressed in pounds per square inch (PSI) in which a water processing device or water system is designed to function.
OPERATING TEMPURATURE
The manufacturer's recommended feed water or inlet water temperature for a water treatment system.
ORIFICE PLATE
A disc, placed in a water flow line, with a concentric sharp-edged circular opening in the center, which creates a differential pressure to measure flow and to operate feeders and instruments or other hydraulic equipment.
OSMOSIS
The natural tendency of water to pass through a semi-permeable membrane, so as to equalize concentrations on both sides of the membrane.
OSMOTIC PRESSURE
The force (pressure) resulting when two liquids, having different solute concentrations, are separated by a semi-permeable membrane. For every 100 ppm, an osmotic "back pressure" of 1 psi is generated and this "back pressure" must be overcome in the reverse osmosis process.
OSTEODYSTROPHY
Abnormal bone development which, in renal patients, may be attributed to parathyroid gland dysfunction and is characterized by high serum phosphorus and alkaline phosphates and low serum calcium levels.
OSTEOMALACIA
A softening of bone due to an accumulation of osteoid and reduced mineralization, which may cause fractures with minimal stress.
OSTEOPOROSIS
Demineralization of bone, which may cause fractures with minimal stress.
OVERFLOW GUTTER
The gutter around the top perimeter of the pool which is used to skim the surface of the water and to carry off the waste, or to collect it for return to the filters (sometimes incorrectly referred to as “scum gutter” or “spit trough”).
OVERFLOW SYSTEM
Refers to removal of pool surface water through the use of overflows, surface skimmers and surface water collection systems of various design and manufacture.
OXIDANTS (OXIDIZING AGENTS)
Chemicals, which provide oxygen and accept an electron in an oxidation-reduction reaction. Free chlorine and chloramines are oxidants, which are widely used for disinfection.
OXIDIZING FILTERS
Filters that use a catalytic media, such as managanous oxides or potassium permangenate, to oxidize iron, manganese and other impurities from water.
OZONE
An extremely active oxidizing agent and bacteriocide, which consists of three oxygen atoms. It is formed by the action of a high voltage electrical field on oxygen or air (such as occurs during an electrical storm). Some degree of ozone can also be produced by certain types of ultraviolet lamps.