Swimming Pool Filters

Sand Filters were introduced over 30 years ago.  The sand filter is perhaps the most popular filter in the market place.  They come in many shapes and sizes, manufactured by a wide range of manufactures, regardless they all have the same mode of operation the water comes in the top of the filter goes through the sand and out the bottom of the filter. The sand is held in place  by a series of laterals at the bottom of the filter. Sand filters use a Silica sand that as been strained to give a uniform size.  It is referred to has pool grade sand # 20 Silica. The sand is normally .45 mm to .55 mm in diameter. As water is passed through the filter, the sharp edges of the sand trap the dirt from the pool water.  When the pressure of the filter increases 3-5 psig., the filter needs to be cleaned, this is usually accomplished  by reversing the flow of the water through the filter and flushing the dirt out the waste pipe. The back wash process is simplified by a Multi-port valve.  The Multi-port Valve is a valve that has several positions on it, one of which is back wash, the pump is turned off and the valve is rotated to the backwash position and the pump is turned on and water flows from the bottom of the filter to the top and causes the trapped particles of dirt to be flushed out the waste port of the filter. After the water run clear (usually 2-3 minutes), the pump is turned off and the valve is rotated to the rinse position.  The rinse position directs water from the top of the filter to the bottom, but not back to the pool.  This process compacts the sand and causes any remaining dirt to be flushed out the waste pipe, rather than back to the pool (usually 30-45 seconds). Once  the rinse cycle is completed, the pump is turned off and the Multi-port valve is returned to the normal or filter position. Once again turn on the pump and the water is returned to the pool. .

Cartridge Filters have been around for many years, but only recently has gained in popularity in the pool industry. Like sand filters Cartridge filters come in many shapes and sizes, What ever the shape or brand, they all work on the same principal water is passed into the tank, the water is forced through the cartridge and the water is returned to the pool. When they Pressure of a Cartridge filter increase approximately 5 psig.   The pump is turned off and the top of the filter is removed, the cartridge is removed and hosed off.  If the filter is below the water level, be sure to close the inlet valves and possible a return valve. After cleaning the cartridge the cartridge is returned to its housing and the lid reassembled.

Diatomaceous Earth (DE):There are three types of DE filters Spin, Regenerative and vertical grids. Once again regardless of type they all work the same way, water comes into the filter, passes through the DE and is returned to the pool.  DE filters are considered the the finest, because they are capable of filtering the smallest particle size of all the filter types. Diatomaceous earth (DE) is a porous powder, made from the skeletons of billions off microscopic animals that died and were buried in deposits millions of years ago.

Spin DE - Spin De filters are designed in a manner that the grids are arranged vertically  along a shaft, that can be turned. This causes the DE to be dislodged and then re-coat the grids, the spin process also aids in cleaning of the grids during the back wash process.

Regenerative DE - The grids are generally tubes, more tubes more filtration, the tubes, hold the DE, as the pressure increases, the grids are bumped and this causes the DE to be dislodge, when the pump is turned on the tubes are re-coated and the DE can be reused.

Vertical Grids- Vertical grids filters use DE, but operate more like sand filters, they usually contain a Back wash system, that when the filter gets dirty you rotate the Multi-port valve to back wash to clean the filter.