diatomaceous earth
Some filters use diatomaceous earth to help filter out contaminants. Commonly known as 'DE' filters, they exhibit superior filtration capabilities.[20] Often, a DE filter will trap waterborne contaminants as small as 1 micrometer. DE filters are banned in some states as they must be emptied periodically and the contaminated media must be flushed down the sewer, causing a problem in some districts' sewer systems.
As of 2020, several companies produce regenerative media filters, sometimes called precoat media filters, that use perlite "Perlite (geology)") as the filtration medium instead of diatomaceous earth. As of 2021, perlite can be safely disposed of down the sewer and is NSF approved and listed for use in the United States.
Other filter media that have been introduced to the residential pool market since 1970 include sand particles and paper-type cartridge filters with a filter area arranged in a compact 12" diameter x 24" long (300 mm x 600 mm) circular accordion-shaped cartridge. These units can be 'daisy-chained' to collectively filter home pools of almost any size. Cartridges are usually cleaned by removing them from the filter body and hosing them through a sewer connection. They are popular where water backwashed from a sand filter is not allowed to discharge or go into the aquifer.
Automatic pool cleaners, more commonly known as "automatic pool cleaners" and, in particular, robotic and electric pool cleaners provide an additional measure of filtration and, in fact, like handheld vacuum cleaners, can microfilter a pool, something that a sand filter without flocculation or coagulants cannot achieve.[21].
These pool cleaners are independent of the pool's main filter and pump system and are powered by a separate electricity source, usually in the form of a fixed transformer that is kept at least 10 feet (3 m) from the pool water, often on the pool deck. They have two internal motors: one to suck water through a self-contained filter bag and then return the filtered water at high speed to the pool water, and another that is a drive motor connected to tractor-like rubber or synthetic tracks and "brushes" connected by rubber or plastic bands through a metal shaft. The brushes, which resemble paint rollers, are located at the front and rear of the machine and help remove contaminating particles from the pool floor, walls, and in some designs, even pool steps (depending on size and configuration). They also direct particles toward the internal filter bag.[22][23].
Salt chlorination units, electronic oxidation systems, ionization systems, microbial disinfection systems with ultraviolet lamps and "Tri-Clor Feeders" are other independent or auxiliary systems to skimmers for pool sanitation.
A consecutive dilution system is available to remove organic waste in stages after passing through the skimmer. The waste matter is trapped within one or more sequential skimmer basket screens, each with a finer mesh to further dilute the size of the contaminant. Dilution here is defined as the action of making something weaker in strength, content or value.
The first basket is placed very close to the mouth of the skimmer. The second is connected to the circulation pump. Here 25% of the water drawn from the main drain at the bottom of the pool meets 75% drawn from the surface. The circulation pump strainer basket is easily accessible for maintenance and should be emptied daily. The third sieve is the sand unit. Here the smaller organic residues that have slipped through the previous sieves are trapped by the sand.
If not removed regularly, organic waste will continue to decompose and affect water quality. The dilution process allows organic waste to be easily removed. Ultimately, the sand screen can be backwashed to remove smaller trapped organic debris that otherwise leaches ammonia and other compounds into the recirculated water. These additional solutes eventually lead to the formation of disinfection byproducts (DBPs). The sieve baskets are easily removed each day for cleaning, as is the litter unit, which should be backwashed at least once a week. A perfectly maintained consecutive dilution system dramatically reduces the buildup of chloramines and other DBPs. The water returned to the pool must have been cleaned of all organic debris greater than 10 microns in size.
"Spa (Health)" Mineral Pool and Spa Disinfectants use minerals, metals or elements derived from the natural environment to produce water quality benefits that would otherwise occur with harsh chemicals or synthetics.
Companies cannot sell a mineral disinfectant in the United States unless it has been registered with the United States Environmental Protection Agency (EPA). Currently, two mineral disinfectants are registered with the EPA: one is a silver salt with a controlled release mechanism that is applied to calcium carbonate granules that help neutralize pH; the other uses a colloidal form of silver released into water from ceramic beads.
Mineral technology takes advantage of the cleaning and filtration qualities of common substances. Silver and copper are well-known oligodynamic substances that are effective in destroying pathogens. Silver has been shown to be effective against harmful bacteria, viruses, protozoa and fungi. Copper is widely used as an algaecide.[24] Alumina, derived from aluminates, filters harmful materials at a molecular level and can be used to control the delivery rate of desirable metals such as copper. Working through the pool or spa's filtration system, mineral sanitizers use combinations of these minerals to inhibit algae growth and remove contaminants.
Unlike chlorine or bromine, metals and minerals do not evaporate and do not degrade. Minerals can make water noticeably softer and, by replacing harsh chemicals in water, reduce the chance of red eyes, dry skin, and bad odors.
Skimmers
Water is normally drawn from the pool through a rectangular opening in the wall, connected through a device installed on one (or more) walls of the pool. The internal parts of the skimmer are accessed from the pool deck through a circular or rectangular cover, about a foot in diameter. If the pool's water pump is operational, water is drawn from the pool through a hinged floating weir (which operates from a vertical position at a 90-degree angle away from the pool, to prevent leaves and debris from flooding into the pool by wave action), and down into a removable "skimmer basket", the purpose of which is to catch leaves, dead bugs, and other larger floating debris.
Another piece of equipment that may be optional in the recirculation system is a pool water heater. They can be heat pumps, natural gas or propane gas heaters, electric heaters, wood heaters or solar hot water panel heaters, increasingly used in the sustainable design of swimming pools.
Diversions to electronic oxidation systems, ionization systems, microbial disinfection systems with ultraviolet lamps and "Tri-Clor Feeders" are other auxiliary systems for pool sanitation - as well as solar panels - and in most cases they are required to be placed after the filtration equipment, often being the last elements placed before the water returns to the pool.