Filters

THERE ARE 3 TYPES OF RESIDENTIAL SWIMMING POOL FILTERS.  SOME CHARACTERISTICS OF EACH ARE SHOWN BELOW

Sand Filters:  The filter housing is filled with sand, which is the filter media.  Dirty water flows down through the sand bed where the dirt is collected.  The clean water flows out the bottom of the filter and back into the pool.  As the filter collects more dirt, it will be more difficult for the water to pass through the sand bed.  As a result, the filter pressure will increase.  Backwashing the filter causes the water to be pumped through the filter in the opposite direction, pushing the dirt out the discharge pipe.  Sand is not lost in this process since the sand particles  are larger and heavier than the dirt.  Once the discharge water is clear, stop the backwash, rinse and go back to the filtration cycle.  After several years, the sand may need to be changed.  This is a rather difficult procedure.

Cartridge Filters:  Here the filter media is a paper cartridge.  The dirty water is pumped from the outside to the inside of the cartridge.  The dirt is collected on the outside of the paper cartridge.  As the cartridge gets dirtier, the pressure will increase.  When the pressure gets about 5 to 8 lbs. above what it was when the cartridge is clean, the filter needs to be removed and hosed off.  The cartridges can be chemically cleaned by soaking in a TSP solution or in extreme situations, a 1 to 4  muriatic acid to water solution.  If, shortly after cleaning, the filter pressure increases quickly or if the filter pressure shows no reduction after cleaning, the filter should be replaced.  Cartridge filters are the only filters that do not come with backwash or waste valves, so in order to be able to waste pool water, a valve must be added.

Diatomaceous Earth Filters:  There are a number of grids (usually 8) inside the filter housing.  The grids consist of a plastic matrix covered with a fabric.  All the grids are connected to a top manifold.  Diatomaceous earth, consisting of tiny ground up fossils, is added into the skimmer where it is pumped into the filter.  The DE is collected on the outside of the fabric covering the grids.  As dirty water is pumped through the filter, the dirt is collected on the surface of the DE powder.  Clean water goes inside the grid and exits through the top manifold.  As the dirt level increases, the filter pressure will increase, indicating that it is time to backwash.  When backwashing, the water is pumped through the manifold inside the grid, forcing both the dirt and DE out the discharge pipe.  Continue backwashing until the water is clear.  After backwashing, new DE must be added into the skimmer.  (Check the filter instructions for the amount of DE to be added.)  Backwashing will not remove all of the DE and dirt.  Therefore, every 6 to 12 months, the filter should be dissassembled and the grids hosed off and checked for any tears in the fabric.  Grids will need to be replaced periodically.  If a customer complains about DE coming back into his pool, this is usually an indication of torn grids.