Three Types Of Swimming Pool and Spa Filters, Sand, DE and Cartridge

There are three types of pool filters, let’s discuss the differences of these units.

The first type of filter is a SANDFILTER, it uses fine filter sand inside a vessel or tank to collect and trap dirt and debris from a swimming pool.  The pool water is sent to the filter from the pool pump to the top of the tank and a fitting inside the vessel called the distributor “rains” the water down and through the sand. As the water migrates down through the bed of sand the pool water is collected by the laterals inside the bottom of tank and returned to the pool filtered and clean. The sand inside the filter can last for many years if the filter is “backwashed”. What is backwashing?  Backwashing is when the water flow inside the filter is reversed (using the selector valve outside the filter) and the dirty water and debris are flushed out through the waste line of the pool system.  Some sand will be lost each time and the level of the pool will be lowered each time the system is backwashed.  When it is time to replace the sand, the old sand will need to be removed, either by hand or tool and the filter will need to be replenished with new fresh filter media.

            The second type of filter is a CARTRIDGE FILTER, it uses a replaceable cartridge element to capture dirt and debris from a pool and or spa. The cartridge is housed in a tank, the upper dome or lid is held on by a knob or clamp and is manufactured with remove ability in mind. When the cartridge has collected enough dirt and debris the cartridge is removed, hosed off, dirt removed and the element is replaced back into the tank.  The cartridge will last for many years if it is cleaned on a regular basis and not allowed to become over filled.  Cartridge filters when cleaned do not require backwashing; the pool water level is unaffected during cleaning. Cartridge filters are a perfect choice for spas due to this fact and the fact of easy of cleaning.

            The third type of filter is a DE FILTER or Diatomaceous Earth unit.  This type of filter has grids which are inside the tank and which hold a thin layer of DE.  As the pool water is sent to the tank from the pool pump it passes through these grids, covered with DE and the DE captures the dirt and debris for removal. DE filters just like sand filters can also be “backwashed” to remove the dirt from inside the filter. Just like the sand filter each time the filter is backwashed, the pool level is lowered and some DE is lost.  Eventually the filter will need to be disassembled, the old DE removed and fresh diatomaceous earth replaced inside the filter.  Fresh DE can be added directly to the filter tank when open.