There are essentially 3 types of water filters used in the pool industry. These are: sand, cartridge and diatomaceous earth (D.E.). Each has its own advantages and disadvantages.

• Sand filters particles as small as 60 microns.
• Cartridges filter particles down to 20 microns.
• DE filters particles down to 10 microns.

 

 

Click here to see how a Sand Filter works

Sand filters are the oldest type of water filter and were actually used by the Romans in their Bath houses. It is the most popular filter media in our area due to its relative ease of use and cost effectiveness. The sand is contained inside a tank. Water is passed through the sand under pressure filtering out particles along the way. At the bottom of the tank there are straining devices called 'laterals'. They contain perforations large enough for the filtered water to pass through but small enough to hold back the sand.

While Sand filters don't do as good of a job filtering as DE or Cartridges, they are relatively maintenance free. When the filter gets dirty, just turn the valve to backwash, then to rinse and back to filter. It is advisable to change your sand once a season in order to keep your filter running efficiently.

This involves disassembling the filter, removing the old sand with a shop vac and discarding it, then refilling the tank with new sand. This can be a big chore as some sand filters hold as much as 600 lbs. of sand.

 

Click here to see how a D.E. filter works

Diatomaceous Earth filters do the best job at filtering water when compared with the others. DE is a fine white powder found in the ground. It is the fossilized skeletons of microscopic sponge-like creatures called 'diatom's'. DE is considered a hazardous material and care should be taken not to breath in the dust. Because of this, it is required that you have a separation tank installed in order to catch the spent Earth.

DE filters contain a vertical array of grids or long tubes known as 'fingers' covered with a plastic mesh material. Like the laterals in a sand filter this mesh lets water pass through but is fine enough to hold the DE back. Water passes through the DE which filters the water and then gets passed back to the pool.

Cleaning a DE filter is a two step process and quite messy. Some DE filters have a backwash valve much like a sand filter, allowing you to rinse the old DE out of the tank. Others require 'bumping', This consists of a lever or knob on top of the tank that forces water through the grids dislodging the Earth. A valve is then opened and a white slurry of DE pours form the filter into a separation tank where it can be disposed of properly.

Also about once every 6 weeks, it is recommended that the filter be taken apart and cleaned. The backwashing process does not dislodge all of the dirty DE powder from the tank. Inevitably it cakes up in the nooks and crannies of the grids reducing the filters performance. The is an extremely messy and time consuming job.

Regardless of the type of DE filter, all require 'recharging'. After backwashing or 'bumping', fresh Earth must be added in order to coat the grids and start filtering again.

 

 

Click here to see how a Cartridge filter works

Cartridge filters work much like DE filters except there is no DE filter media. A filter cartridge looks much like the air filter on your car. This type of filter contains on or more pleated cartridges made of tightly woven polyester. The pleats enable an extremely large surface area to be packed into a small area. Cartridge filters have been gaining in popularity over the past five years. They are inexpensive, filter particles almost as small as DE but are much less messy and easier to clean. When the cartridges get Dirty, simply pull them out, hose them off, and replace. Most Hot Tubs use Cartridge filters because of this. Once or twice a season it is recommended that you soak the cartridges in a chemical cleaner in order to remove the body oils and lotions that accumulate in the fabric. Most people have 2 sets of cartridges and leave one set soaking. This makes maintenance a breeze, simply remove the dirty cartridges, rinse, place them in a cleaning solution, and put your cleaned cartridges back in your filter.