On Swimming Pool Filtration System  

by Pool Builders on 04-23-2013 in Articles

A pool filtration system as described is termed a consecutive dilution system, as a constant and consecutive stream of fresh, chlorinated, and filtered water is being continually returned to the pool as part of a process that could ultimately result in a pool with 100 percent newly introduced fresh water over a period of time. Of course this goal is never achieved, as there is also a constant stream of new contaminants entering the pool. We can name some filtration units, the first is the sand. In this system, 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 of particles no less than 10 micrometers in size. The rapid sand filter type is periodically back washed as contaminants reduce water flow and increase back pressure. Indicated by a pressure gauge 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 will last five to seven years before all the rough edges are worn off and the more tightly packed sand no longer works as intended. Recommended filtration for public/commercial pools are 1 ton sand per 100,000 liters water.

Introduced in the early 1900s was the another type off sand filter, the rapid sand filter, whereby water was pumped into the top of a large volume tank 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. This type of filters is not greatly effective, and is no longer common in home swimming pools, being replaced by the pressure-fed type filters. The Diatomaceous Earth is used to filter out contaminants. Commonly referred to as D.E. filters, they exhibit superior filtration capabilities. Often a DE filter will trap water-borne contaminants as small as 1 micrometer in size. DE filters are banned in some states, as they must be emptied out periodically and the contaminant media flushed down the sewer, causing a problem in some districts sewage systems.

The cartridge filters are other filter media that have been introduced to the residential swimming pool market since 1970 include sand particles and paper type cartridge filers of 50 to 150 square feet (14 cubic meter) filter are arranged in a tightly packed 12 inches diameter x 24 inches long accordion-like circular cartridge. These units can be daisy-chained together to collectively filter almost any size home pool. The cartridges are typically cleaned by removal from the filter body and hosing-off down a sewer connection. They are popular where backwash water from a sand filter is not allowed to be discharge or goes into the aquifer.

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