Pool filters work to remove particles from pool water. While chemicals can kill bacteria present in the water, they cannot remove the dead bacteria, and they cannot do anything about minerals or organic waste that accumulates in the pool. The filter removes these contaminants before they can do any damage. Sand filters are one of the most common types of filters, but they require special sand sold at pool and spa stores.
A sand filter is essentially a cylinder partially filled with sand. The water is pumped through this filter and then drawn through the sand. Any particles in the water become trapped in the sand, while the water flows easily through. The water, now clean, is pumped back into the pool while valves keep the sand in place.
Owners of sand filters must be sure to buy specific types of sand for their systems. Ordinary sand found at the beach will not work: pool sand is made of very small, fine grains. The finer the sand, the more easily it can trap small particles while letting water flow through. Normal sand is to angular and large to be effective at the filtration process.
Places to Look
Owners of sand filters should look at local pool stores for bags of filter sand, usually available in five- or 10-pound quantities. There are several different brands of pool sand, and while some filters are meant to be used with certain types of sand, there is little difference between the brands. Owners should look for sand by Quikrete, HTH, Aqua Quartz or Zeosand.
Those with pool filters should also look at what the sand is made out of. One of the most popular materials is silica, which is a very effective filtering material but can be dangerous to inhale. Some manufacturers, such as Zeosand, make their sand out of green zeolite, which is also acceptable.
Sand filters typically have backwash systems that get rid of the contaminants that the sand collects. It is not common for filters to run out of sand, especially not within the first few years of service. Sand only leaves the filter when valves break, and with proper cleaning techniques, the same sand can be re-used for much of the filter's life.