Typical filtration equipment used in private swimming pools
Water pump
An electrically operated water pump is the prime motivator in recirculating the water from the pool. Water is forced through a filter and then returned to the pool. A typical pool pump uses 500 watts to 2,000 Kilowatts. Pumps are typical run for 4 hours per day in winter (when the pool is not in use) and up to 24 hours in summer. To save electricity costs most people run for between 6 hours and 12 hours in summer with the pump being controlled by an electronic timer.
Some pool pumps have two motor speeds to reduce power consumption at times when full power is not needed. Other pump manufacturers (typically Italian or other European) have redesigned their units to use a smaller electric motor with heavier windings, therefore consuming less energy, to power a larger pump impeller.
Pool pumps typically are "self priming": they may be positioned above the mean water level of the pool yet still start up and function after a timed rest period. Pumps that do not "self prime" are termed "flooded suction" and must be gravity fed by the pool by being located below the mean level of the pool water.
Most pool pumps available today incorporate a small filter basket termed a "hair and lint strainer" or "lint pot" as the last effort to avoid leaf or hair contamination reaching the close-tolerance impeller section of the pump.
[edit] Filter Unit
A pressure-fed filter is typically placed in line immediately after the water pump. The filter typically contains a media such as graded sand (called ¡¯14/24 Filter Media¡¯ in the UK system of grading the size of sand by sifting through a fine brass-wire mesh of 14 to the inch to 24 to the inch). A pressure fed sand filter is termed a ¡¯High Rate¡¯ sand filter, and will generally filter turbid water down to 10 micrometers in size.[2] The rapid sand filter type are periodically ¡¯back washed¡¯ as contaminants reduce water flow and increase back pressure. Indicated by a pressure gage on the pressure side of the filter reaching into the ¡¯red line¡¯ area, the pool owner is alerted to the need to ¡¯backwash¡¯ the unit. The sand in the filter will typically last five to seven years before all the "rough edges" are worn off and the more tightly packed sand no longer works as intended.
Introduced in the early 1900s was another type of sand filter; the ¡¯Rapid Sand¡¯ filter, whereby water was pumped into the top of a large volume tank (3¡¯ 0" or more cube) containing filter grade sand, and returning to the pool through a pipe at the bottom of the tank. As there is no pressure inside this tank, they were also known as ¡¯gravity filters¡¯. These type of filters are not greatly effective, and are no longer common in home swimming pools, being replaced by the pressure-fed type filter.
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