Swimming pool filters
A well-maintained pool filter is the key to a healthy and sparkling pool. A good filtration system for swimming pool requires us to size the filter properly. Regardless of whether to replace an old filter or install a brand new filter, we’ll need to match the filter to the pump. We will talk about filter sizing in subsequent article.
There are three types of swimming pool filters, D.E. (Diatomaceous Earth) filter, Sand and Cartridge filters. The selection of the type of filter will depends on the customers’ preference and often the site condition. Most home owner will prefer D.E. filter, over Sand filter and Cartridge filters. The advice will be always buys the largest filter you can afford!
D.E. (Diatomaceous Earth) Filters
Water will follow through filter tank which contains filter element. For DE filter to work, the filter element has to be coated with the Diatomaceous Earth powder (a fine powder made from the chemically inert, fossilized remains of sea organisms). Typically each filter will has 8 pieces of elements with filtration area from 24 to 72 square feet. Filtration level is up to 5 micron which is best among other type of filters. Only disadvantage is that the element grids have to be re-coated with Diatomaceous Earth powder after each back-wash. The physical footprint is smaller than sand filter with diameter of only 55 cm.
Sand filters consist of a large tank, made of fiberglass or plastic and inside contain a thick bed of fine silica sand sized #20 or 0.45 to 0.55mm. The dirty water enters the top or side of the sand filter and sprays over the sand. The water flow through the sand media and the sharp edges of the sand will trap the dirt and impurities. Then the water is pushed through the laterals and out of the sand filter. Filtration area is much smaller than D.E. Filters. Filtration level is up to 25 micron. We can increase the filtration level to up to 2 micron if we replace the sand with extremely porous volcanic media called Zeolite. Silica sand media is able to last 5 to 15 years if you maintain the sand filter by the regular back-wash.
The design of the cartridge filters is similar to D.E. filter except there is no need for D.E. powder. Water will flows through the cylindrical cartridges of fine pleated mesh material (polyester). Filtration area starts from 25 square feet to up to 200 square feet. Filtration level is up to 10 micron. We cannot back-wash the cartridge element, they are removed and washed.