
Swimming pool sanitation is the process of ensuring healthy conditions in
swimming pool
A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable Human swimming, swimming and associated activities. Pools can be built into the ground (in-ground pools) or built abo ...
s. Proper sanitation is needed to maintain the
visual clarity of water and to prevent the transmission of infectious
waterborne diseases
Waterborne diseases are conditions (meaning adverse effects on human health, such as death, disability, illness or disorders) caused by pathogenic micro-organisms that are transmitted by water. These diseases can be spread while bathing, washing ...
.
Methods
Two distinct and separate methods are employed in the sanitation of a swimming pool. The
filtration system removes
organic waste
Biodegradable waste includes any organic matter in waste which can be broken down into carbon dioxide, water, methane, compost, humus, and simple organic molecules by micro-organisms and other living things by composting, aerobic digestion, ana ...
on a daily basis by using the sieve baskets inside the skimmer and circulation pump and the sand unit with a backwash facility for easy removal of organic waste from the water circulation.
Disinfection
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
- normally in the form of
hypochlorous acid
Hypochlorous acid is an inorganic compound with the chemical formula , also written as HClO, HOCl, or ClHO. Its structure is . It is an acid that forms when chlorine dissolves in water, and itself partially dissociates, forming a hypochlorite an ...
(HClO) - kills infectious
microorganism
A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...
s. Alongside these two distinct measures within the pool owner's jurisdiction, swimmer hygiene and cleanliness helps reduce organic waste build-up.
Guidelines
The
World Health Organization
The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
has published international guidelines for the safety of swimming pools and similar recreational-water environments, including standards for minimizing microbial and chemical hazards. The United States
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency under the United S ...
also provides information on pool sanitation and water related illnesses for health professionals and the public. The main organizations providing certifications for pool and spa operators and technicians are the National Swimming Pool Foundation and Association of Pool & Spa Professionals. The certifications are accepted by many state and local health departments.
Contaminants and disease
Swimming pool
contaminants
Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for the physical body, natural environment, workplace, etc.
Types of contamination
Within the scie ...
are introduced from environmental sources and swimmers. Affecting primarily outdoor swimming pools, environmental contaminants include windblown dirt and debris, incoming water from unsanitary sources,
rain
Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...
containing microscopic
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
spores and droppings from birds possibly harboring disease-causing pathogens.
Indoor pools are less susceptible to environmental contaminants.
Contaminants introduced by swimmers can dramatically influence the operation of indoor and outdoor swimming pools. Contaminants include micro-organisms from infected swimmers and body oils including
sweat
Perspiration, also known as sweat, is the fluid secreted by sweat glands in the skin of mammals.
Two types of sweat glands can be found in humans: eccrine glands and Apocrine sweat gland, apocrine glands. The eccrine sweat glands are distribu ...
,
cosmetics
Cosmetics are substances that are intended for application to the body for cleansing, beautifying, promoting attractiveness, or altering appearance. They are mixtures of chemical compounds derived from either Natural product, natural source ...
,
suntan lotion,
urine
Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...
,
saliva
Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which ...
and
fecal matter; for example, it was estimated by researchers that swimming pools contain, on average, 30 to 80 mL of urine for each person that uses the pool. In addition, the interaction between disinfectants and pool water contaminants can produce a mixture of chloramines and other
disinfection by-product
Disinfection by-products (DBPs) are organic and inorganic compounds resulting from chemical reactions between organic and inorganic substances such as contaminates and chemical treatment disinfection agents, respectively, in water during water di ...
s. The journal ''
Environmental Science & Technology
''Environmental Science & Technology'' is a biweekly peer-reviewed scientific journal published since 1967 by the American Chemical Society. It covers research in environmental science and environmental technology, including environmental policy. ...
'' reported that sweat and urine react with chlorine and produce
trichloramine
Nitrogen trichloride, also known as trichloramine, is the chemical compound with the formula . This yellow, oily, and explosive liquid is most commonly encountered as a product of chemical reactions between ammonia-derivatives and chlorine (for ex ...
and
cyanogen chloride
Cyanogen chloride is an inorganic compound with the formula . This triatomic pseudohalogen is an easily condensed colorless gas. More commonly encountered in the laboratory is the related compound cyanogen bromide, a room-temperature solid that is ...
, two chemicals dangerous to human health
An answer to the perennial question: Is it safe to pee in the pool?Nitrosamine
Nitrosamines (or more formally ''N''-nitrosamines) are organic compounds produced by industrial processes. The chemical structure is , where R is usually an alkyl group. Nitrosamines have a nitroso group () that are "probable human carcinogens", ...
s are another type of the
disinfection by-products
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
that are of concern as a potential health hazard.
[
]Acesulfame potassium
Acesulfame potassium (, or ), also known as acesulfame K or Ace K, is a synthetic calorie-free sugar substitute (artificial sweetener) often marketed under the trade names Sunett and Sweet One. In the European Union, it is known under the E n ...
is widely used in the human diet and excreted by the kidneys. It has been used by researchers as a marker to estimate the degree to which swimming pools are contaminated by urine. It was estimated that a commercial-size swimming pool of 220,000 gallons would contain about 20 gallons of urine, equivalent to about 2 gallons of urine in a typical residential pool.[
Pathogenic contaminants are of greatest concern in swimming pools as they have been associated with numerous recreational water illnesses (RWIs).] Public health pathogens can be present in swimming pools as viruses, bacteria, protozoa and fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
. Diarrhea
Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
is the most commonly reported illness associated with pathogenic contaminants, while other diseases associated with untreated pools are Cryptosporidiosis
Cryptosporidiosis, sometimes informally called crypto, is a parasitic disease caused by ''Cryptosporidium'', a genus of protozoan parasites in the phylum Apicomplexa. It affects the ileum, distal small intestine and can affect the respiratory tr ...
and Giardiasis
Giardiasis is a parasitic disease caused by the protist enteropathogen ''Giardia duodenalis'' (also known as ''G. lamblia'' and ''G. intestinalis''), especially common in children and travellers. Infected individuals experience steatorrhea, a typ ...
. Other illnesses commonly occurring in poorly maintained swimming pools include otitis externa
Otitis externa, also called swimmer's ear, is inflammation of the ear canal. It often presents with ear pain, swelling of the ear canal, and occasionally decreased hearing. Typically there is pain with movement of the outer ear. A high fever ...
, commonly called swimmers ear, skin rashes and respiratory infections.
Maintenance and hygiene
Contamination can be minimized by good swimmer hygiene practices such as showering before and after swimming, and not letting children with intestinal disorders swim. Effective treatments are needed to address contaminants in pool water because preventing the introduction of pool contaminants, pathogenic and non-pathogenic, into swimming pools is, in practice, impossible.
A well-maintained, properly operating pool filtration
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filte ...
and re-circulation system is the first barrier, combating the contaminants large enough to be filtered. Rapid removal of these filterable contaminants reduces the impact on the disinfection system thereby limiting the formation of chloramine
Monochloramine, often called chloramine, is the chemical compound with the formula NH2Cl. Together with dichloramine (NHCl2) and nitrogen trichloride (NCl3), it is one of the three chloramines of ammonia. It is a colorless liquid at its melting ...
s, restricting the formation of disinfection by-product
Disinfection by-products (DBPs) are organic and inorganic compounds resulting from chemical reactions between organic and inorganic substances such as contaminates and chemical treatment disinfection agents, respectively, in water during water di ...
s and optimizing sanitation effectiveness. To kill pathogens and help prevent recreational water illnesses, pool operators must maintain proper levels of chlorine or another sanitizer.
Over time, calcium from municipal water tends to accumulate, developing salt deposits in the swimming pool walls and equipment (filters, pumps), reducing their effectiveness. Therefore, it is advised to either completely drain the pool, and refill it with fresh water, or recycle the existing pool water, using reverse osmosis
Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane, semi-permeable membrane to separate water molecules from other substances. RO applies pressure to overcome osmotic pressure that favors even distribu ...
. The advantage of the latter method is that 90% of the water can be reused.
Pool operators must also store and handle cleaning and sanitation chemicals safely.
Prevention of diseases in swimming pools and spas
Disease prevention should be the top priority for every water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
management program for pool and spa operators. Disinfection is critical to protect against pathogens, and is best managed through routine monitoring and maintenance of chemical feed equipment to ensure optimum chemical levels in accordance with state and local regulations.
Chemical parameters include disinfectant levels according to regulated pesticide label directions. pH should be kept between 7.2 and 7.8. Human tears have a pH of 7.4, making this an ideal point to set a pool. More often than not, it is improper pH and not the sanitiser that is responsible for irritating swimmers' skin and eyes.
Total alkalinity should be 80–120 ppm and calcium hardness
In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...
between 200 and 400 ppm.
Good hygienic behavior at swimming pools is also important for reducing health risk factors at swimming pools and spas. Showering before swimming can reduce introduction of contaminants to the pool, and showering again after swimming will help to remove any that may have been picked up by the swimmer.
Those with diarrhea
Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...
or other gastroenteritis
Gastroenteritis, also known as infectious diarrhea, is an inflammation of the Human gastrointestinal tract, gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of ...
illnesses should not swim within 2 weeks of an outbreak, especially children. Cryptosporidium
''Cryptosporidium'', sometimes called crypto, is an apicomplexan genus of alveolates which are parasitism, parasites that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea (inte ...
is chlorine resistant.
In order to minimize exposure to pathogens, swimmers should avoid getting water into their mouths, and should never swallow pool or spa water.
Standards
Maintaining an effective concentration of disinfectant is critically important in assuring the safety and health of swimming pool and spa users. When any of these pool chemicals are used, it is very important to keep the pH of the pool in the range 7.2 to 7.8 – according to the Langelier Saturation Index, or 7.8 to 8.2 – according to the Hamilton Index; higher pH drastically reduces the sanitizing power of the chlorine due to reduced oxidation-reduction potential (ORP), while lower pH produces more rapid loss of chlorine and causes bather discomfort, especially to the eyes. However, according to the Hamilton Index, a higher pH can reduce unnecessary chlorine consumption while still remaining effective at preventing algae and bacteria growth.
To help ensure the health of bathers and protect pool equipment, it is essential to perform routine monitoring of water quality factors (or "parameters") on a regular basis. This process becomes the essence of an optimum water quality management program.
Systems and disinfection methods
Chlorine and bromine methods
Conventional halogen-based oxidizers such as chlorine
Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
and bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
are convenient and economical primary sanitizers for swimming pools and provide a residual level of sanitizer that remains in the water. Chlorine-releasing compounds are the most popular and frequently used in swimming pools whereas bromine-releasing compounds have found heightened popularity in spas and hot tubs. Both are members of the halogen
The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...
group with demonstrated ability to destroy and deactivate a wide range of potentially dangerous bacteria and viruses in swimming pools and spas. Both exhibit three essential elements as ideal first-line-of-defense sanitizers for swimming pools and spas: they are fast-acting and enduring, they are effective algaecides, and they oxidize undesired contaminants.
Swimming pools can be disinfected with a variety of chlorine-releasing compounds. The most basic of these compounds is molecular chlorine (Cl2); however, its application is primarily in large commercial public swimming pools. Inorganic forms of chlorine-releasing compounds frequently used in residential and public swimming pools include sodium hypochlorite
Sodium hypochlorite is an alkaline inorganic chemical compound with the formula (also written as NaClO). It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of ...
commonly known as liquid bleach or simply bleach
Bleach is the generic name for any chemical product that is used industrially or domestically to remove color from (i.e. to whiten) fabric or fiber (in a process called bleaching) or to disinfect after cleaning. It often refers specifically t ...
, calcium hypochlorite
Calcium hypochlorite is an inorganic compound with chemical formula , also written as . It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow decomposition in moist air. This compound is ...
and lithium hypochlorite
Lithium hypochlorite is a chemical compound with the chemical formula of . It is the lithium salt of hypochlorous acid. It consists of lithium cations () and hypochlorite anions (). It is a colorless, crystalline compound. It has been used as a di ...
. Chlorine residuals from Cl2 and inorganic chlorine-releasing compounds break down rapidly in sunlight
Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...
. To extend their disinfectant usefulness and persistence in outdoor settings, swimming pools treated with one or more of the inorganic forms of chlorine-releasing compounds can be supplemented with cyanuric acid
Cyanuric acid or 1,3,5-triazine-2,4,6-triol is a chemical compound with the chemical formula, formula (CNOH)3. Like many industrially useful chemicals, this triazine has many synonyms. This white, odorless solid finds use as a precursor or a com ...
– a granular stabilizing agent capable of extending the active chlorine residual half-life Half-life is a mathematical and scientific description of exponential or gradual decay.
Half-life, half life or halflife may also refer to:
Film
* Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang
* ''Half Life: ...
(t½) by four to sixfold.
Chlorinated isocyanurates, a family of organic chlorine-releasing compounds, are stabilized to prevent UV degradation due to the presence of cyanurate as part of their chemical backbone. These are commonly sold for general use in small summer pools, where the water is expected to be used for only a few months and is expected to be regularly topped up with fresh, due to evaporation and splash loss. It is important to change the water frequently, otherwise, levels of cyanuric acid will build up to beyond the point at which the mechanism functions. Excess cyanurates will actually work in reverse and will inhibit the chlorine. A steadily lowering pH value of the water may at first be noticed. Algal growth may become visible, even though chlorine tests show sufficient levels.
Chlorine reacting with urea
Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...
in urine and other nitrogen-containing wastes from bathers can produce chloramines
Chloramines refer to derivatives of ammonia and organic amines wherein one or more N−H bonds have been replaced by N−Cl bonds. Two classes of compounds are considered: inorganic chloramines and organic chloramines. Chloramines are the most wi ...
. Chloramines typically occur when an insufficient amount of chlorine is used to disinfect a contaminated pool. Chloramines are generally responsible for the noxious, irritating smell prominently occurring in indoor pool settings. A common way to remove chloramines is to "superchlorinate" (commonly called "shocking") the pool with a high dose of inorganic chlorine sufficient to deliver 10 ppm chlorine. Regular superchlorination (every two weeks in summer) helps to eliminate these unpleasant odors in the pool. Levels of chloramines and other volatile compounds in water can be minimized by reducing contaminants that lead to their formation (e.g., urea, creatinine, amino acids and personal care products) as well as by use of non-chlorine "shock oxidizers" such as potassium peroxymonosulfate
Potassium peroxymonosulfate is widely used as an oxidizing agent, for example, in pools and spas (usually referred to as monopersulfate or "MPS"). It is the potassium salt (chemistry), salt of peroxymonosulfuric acid. Potassium peroxymonosulfate ...
.
Medium pressure UV technology is used to control the level of chloramines in indoor pools. It is also used as a secondary form of disinfection to address chlorine-tolerant pathogens. A properly sized and maintained UV system should remove the need to shock for chloramines, although shocking would still be used to address a fecal accident in the pool. UV will not replace chlorine but is used to control the level of chloramines, which are responsible for the odor, irritation, and enhanced corrosion at an indoor pool.
Copper ion system
Copper ion systems use an electric current
An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge c ...
across .500 gm bars (solid copper, or a mixture of copper and .100 gm or silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
) to free copper ions into the flow of pool water to kill organisms
An organism is any living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been pr ...
such as algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
in the water and provide a "residual" in the water. Alternative systems also use titanium
Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
plates to produce oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
in the water to help degrade organic compound
Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
s.
Private pool filtration
Water pumps
An electrically operated water pump
A pump is a device that moves fluids (liquids or gases), or sometimes Slurry, slurries, by mechanical action, typically converted from electrical energy into hydraulic or pneumatic energy.
Mechanical pumps serve in a wide range of application ...
is the prime motivator in recirculating the water from the pool. Water is forced through a filter and then returned to the pool. Using a water pump by itself is often not sufficient to completely sanitize a pool. Commercial and public pool pumps usually run 24 hours a day for the entire operating season of the pool. Residential pool pumps are typically run for 4 hours per day in winter (when the pool is not in use) and up to 24 hours in summer. To save electricity costs, most pools run water pumps for between 6 hours and 12 hours in summer with the pump being controlled by an electronic timer
A timer or countdown timer is a type of clock that starts from a specified time duration and stops upon reaching 00:00. It can also usually be stopped manually before the whole duration has elapsed. An example of a simple timer is an hourglass ...
.
Most pool pumps available today incorporate a small filter basket as the last effort to avoid leaf or hair contamination reaching the close-tolerance impeller section of the pump.
Filtration units
Sand
A pressure-fed sand filter
Sand filters are used as a step in the water treatment process of water purification.
There are three main types; rapid (gravity) sand filters, upward flow sand filters and slow sand filters. All three methods are used extensively in the water ...
is typically placed in line immediately after the water pump. The filter typically contains a medium such as graded sand (called '14/24 Filter Media' in the UK system of grading the size of sand by sifting through a fine brass-wire mesh of 14 to the inch (5.5 per centimeter) to 24 to the inch (9.5 per cm)). A pressure fed sand filter is termed a 'High Rate' sand filter, and will generally filter turbid water of particulates no less than 10 micrometers
The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...
in size. The rapid sand filter
The rapid sand filter or rapid gravity filter is a type of filter used in water purification and is commonly used in municipal drinking water facilities as part of a multiple-stage treatment system. These systems are complex and expensive to ope ...
type are periodically 'back washed' as contaminants reduce water flow and increase back pressure. Indicated by a pressure gauge on the pressure side of the filter reaching into the 'red line' area, the pool owner is alerted to the need to 'backwash' the unit. The sand in the filter will typically last five to seven years before all the "rough edges" are worn off, and the more tightly packed sand no longer works as intended . Recommended filtration for public/commercial pools is 1 ton sand per 100,000 liters water (10 ounces avdp. per cubic foot of water) .48 US or 6.23 UK gallons
Introduced in the early 1900s was another type of sand filter – the 'Rapid Sand' filter, whereby water was pumped into the top of a large volume tank (3' 0" or more cube) (1 cubic yard/200US gal/170UK gal/770 liters) containing filter grade sand and returning to the pool through a pipe at the bottom of the tank. As there is no pressure inside this tank, they were also known as "gravity filters". These types of filters are not greatly effective, and are no longer common in home swimming pools, being replaced by the pressure-fed type filter.
Diatomaceous earth
Some filters use diatomaceous earth
Diatomaceous earth ( ), also known as diatomite ( ), celite, or kieselguhr, is a naturally occurring, soft, siliceous rock, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging fr ...
to help filter out contaminants. Commonly referred to as 'D.E.' filters, they exhibit superior filtration capabilities. Often a D.E. filter will trap waterborne contaminants as small as 1 micrometer in size. D.E. filters are banned in some states, as they must be emptied out periodically and the contaminated media flushed down the sewer, causing a problem in some districts' sewage systems.
As of 2020, several companies now produce regenerative media filters, sometimes called precoat media filters, which use perlite
Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the Hydrate, hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an indu ...
as the filtration media rather than diatomaceous earth. As of 2021, perlite can safely be flushed down the sewer and is approved and NSF
NSF may stand for:
Political organizations
*National Socialist Front, a Swedish National Socialist party
*NS-Frauenschaft, the women's wing of the former German Nazi party
* National Students Federation, a leftist Pakistani students' political g ...
listed for use in the United States.
Cartridge filters
Other filter media that have been introduced to the residential swimming pool market since 1970 include sand particles and paper type cartridge filters of filter area arranged in a tightly packed 12" diameter x 24" long (300 mm x 600 mm) accordion-like circular cartridge. These units can be 'daisy-chained' together to collectively filter almost any size home pool. The cartridges are typically cleaned by removal from the filter body and hosing-off down a sewer connection. They are popular where backwashed water from a sand filter is not allowed to be discharged or go into the aquifer
An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...
.
Fabric Filters
Traditional pool filters vary in the micron particle sizes that they can capture. Fabric filters can capture particles smaller than that of standard swimming pool filtration systems. This type of filter connects where the water return to the pool after passing through a standard filter. They are usually in the form of a bag. With filtration levels as small as 1 micrometer, users can attain much cleaner water, when using a sand of cartridge filter. These levels are equal or better than that of a diatomaceous earth
Diatomaceous earth ( ), also known as diatomite ( ), celite, or kieselguhr, is a naturally occurring, soft, siliceous rock, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging fr ...
filter.
Automated pool cleaners
Automated pool cleaners more commonly known as "Automatic pool cleaners" and in particular electric, robotic pool cleaners provide an extra measure of filtration, and in fact like the handheld vacuums can microfilter a pool, which a sand filter without flocculation or coagulants is unable to accomplish.
These cleaners are independent from the pool's main filter and pump system and are powered by a separate electricity source, usually in the form of a set-down transformer that is kept at least from the water in the pool, often on the pool deck. They have two internal motors: one to suck in water through a self-contained filter bag and then return the filtered water at a high speed back into the pool water, and one that is a drive motor connected to tractor-like rubber or synthetic tracks and "brushes" connected by rubber or plastic bands via a metal shaft. The brushes, resembling paint rollers, are located on the front and back of the machine, and help to remove contaminating particles from the pool's floor, walls, and, in some designs, even the pool steps (depending on size and configuration). They also direct the particles into the internal filter bag.
Other systems
Saline chlorination units, electronic oxidation systems, ionization systems, microbe disinfection with ultra-violet lamp systems, and "Tri-Chlor Feeders" are other independent or auxiliary systems for swimming pool sanitation.
Consecutive dilution
A consecutive dilution system is arranged to remove organic waste in stages after it passes through the skimmer. Waste matter is trapped inside one or more sequential skimmer basket sieves, each having a finer mesh to further dilute contaminant size. Dilution here is defined as the action of making something weaker in force, content, or value.
The first basket is placed closely after the skimmer mouth. The second is attached to the circulation pump. Here the 25% of water drawn from the main drain at the bottom of the swimming pool meets the 75% drawn from the surface. The circulation pump sieve basket is easily accessible for service and is to be emptied daily. The third sieve is the sand unit. Here smaller organic waste that has slipped through the previous sieves is trapped by sand.
If not removed regularly, organic waste will continue to rot down and affect water quality. The dilution process allows organic waste to be easily removed. Ultimately the sand sieve can be backwashed to remove smaller trapped organic waste which otherwise leaches ammonia and other compounds into the recirculated water. These additional solutes eventually lead to the formation of disinfection by-products
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
(DBP's). The sieve baskets are easily removed daily for cleaning as is the sand unit, which should be back-washed at least once a week. A perfectly maintained consecutive dilution system drastically reduces the build-up of chloramines and other DBP's. The water returned to the pool should have been cleared of all organic waste above 10 microns in size.
Mineral sanitizers
Mineral sanitizers for the swimming pool
A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable Human swimming, swimming and associated activities. Pools can be built into the ground (in-ground pools) or built abo ...
and spa use mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
s, metal
A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...
s, or elements derived from the natural environment to produce water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
benefits that would otherwise be produced by harsh or synthetic chemical
A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...
s.
Companies are not allowed to sell a mineral sanitizer in the United States unless it has been registered with the United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent agency of the United States government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on De ...
(EPA). Currently, two mineral sanitizers are registered with the EPA: one is a silver salt with a controlled release mechanism which 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 cleansing and filtering
Filtration is a physical process that separates solid matter and fluid from a mixture.
Filter, filtering, filters or filtration may also refer to:
Science and technology
Computing
* Filter (higher-order function), in functional programming
* Fil ...
qualities of commonly occurring substances. Silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
and copper
Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
are well-known oligodynamic substances that are effective in destroying pathogen
In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
s. Silver has been shown to be effective against harmful bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
, virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...
es, protozoa
Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...
and fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
. Copper is widely used as an algicide
Algaecide or algicide is a biocide used for killing and preventing the growth of algae, often defined in a loose sense that, beyond the biological definition, also includes cyanobacteria ("blue-green algae"). An algaecide may be used for controlled ...
. Alumina
Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly ...
, derived from aluminates, filters detrimental materials at the molecular level and can be used to control the delivery rate of desirable metals such as copper. Working through the pool or spa filtration system, mineral sanitizers use combinations of these minerals to inhibit algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
growth and eliminate contaminants.
Unlike chlorine
Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
or bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
, metals and minerals do not evaporate and do not degrade. Minerals can make the water noticeably softer, and by replacing harsh chemicals in the water they lower the potential for red-eye, dry skin
Xeroderma, xerosis or xerosis cutis, or simply dry skin, is a skin condition characterized by excessively dry skin. The term derives .
In most cases, dry skin can safely be treated with moisturizers (also called emollients). Xeroderma occurs ...
and foul odors.
Skimmers
Coping apertures
Water is typically drawn from the pool via a rectangular aperture in the wall, connected through to a device fitted into one (or more) wall/s of the pool. The internals of the skimmer are accessed from the pool deck through a circular or rectangle lid, about one foot in diameter. If the pool's water pump is operational water is drawn from the pool over a floating hinged weir
A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the water level. Weirs are also used to control the flow of water for outlets of l ...
(operating from a vertical position to a 90-degree angle away from the pool, in order to stop leaves and debris being back-flooded into the pool by wave action), and down into a removable "skimmer basket", the purpose of which is to entrap leaves, dead insects and other larger floating debris.
The aperture visible from the pool side is typically 1' 0" (300 mm) wide by 6" (150 mm) high, which intersects the water midway through the center of the aperture. Skimmers with apertures wider than this are termed "wide angle" skimmers and may be as much as 2' 0" wide (600 mm). Floating skimmers have the advantage of not being affected by the level of the water as these are adjusted to work with the rate of pump suction and will retain optimum skimming regardless of water level leading to a markedly reduced amount of bio-material in the water. Skimmers should always have a leaf basket or filter between it and the pump to avoid blockages in the pipes leading to the pump and filter.
Prior to the mid 1970s most skimmers were either made of metal like copper or stainless steel either a large round or square shape. Built in concrete pour skimmers were also common on concrete pools before the introduction of PVC Skimmers in the late 1960s
Pool re-circulation
Water returning from the consecutive dilution system is passed through return jets below the surface. These are designed to impact a turbulent flow as the water enters the pool. This flow as a force is far less than the mass of water in the pool and takes the least pressure route upward where eventually surface tension reforms it into a laminar flow on the surface.
As the returned water disturbs the surface, it creates a capillary wave. If the return jets are positioned correctly, this wave creates a circular motion within the surface tension of the water, allowing that on the surface to slowly circulate around the pool walls. Organic waste floating on the surface through this circulation from the capillary wave is slowly drawn past the mouth of the skimmer where it is pulled in due to the laminar flow and surface tension over the skimmer weir. In a well-designed pool, circulation caused by the disturbed returned water aids in removing organic waste from the pool surface, directing it to be trapped inside the consecutive dilution system for easy disposal.
Many return jets are equipped with a swivel nozzle. Used correctly, it induces deeper circulation, further cleaning the water. Turning the jet nozzles at an angle imparts rotation within the entire depth of pool water. Orientation to the left or right would generate clockwise or anti-clockwise rotation respectively. This has the benefit of cleaning the bottom of the pool and slowly moving sunken inorganic debris to the main drain where it is removed by the circulation pump basket sieve.
In a correctly constructed pool, rotation of the water caused by the manner it is returned from the consecutive dilution system will reduce or even waive the need to vacuum the bottom. To gain the maximum rotation force on the main body of water, the consecutive dilution system needs to be as clean and unblocked as possible to allow maximum flow pressure from the pump. As the water rotates, it also disturbs organic waste at lower water layers, forcing it to the top. Rotational force the pool return jets create is the most important part of cleaning the pool water and pushing organic waste across the mouth of the skimmer.
With a correctly designed and operated swimming pool, this circulation is visible and after a period of time, reaches even the deep end, inducing a low-velocity vortex above the main drain due to suction. Correct use of the return jets is the most effective way of removing disinfection by-products caused by deeper decomposing organic waste and drawing it into the consecutive dilution system for immediate disposal.
Heaters
Another piece of equipment that may be optioned in the recirculation system is a pool water heater. They can be heat pump
A heat pump is a device that uses electricity to transfer heat from a colder place to a warmer place. Specifically, the heat pump transfers thermal energy using a heat pump and refrigeration cycle, cooling the cool space and warming the warm s ...
s, natural gas or propane gas heaters, electric heaters, wood-burning heaters, or Solar hot water panel heaters – increasingly used in the sustainable design
Environmentally sustainable design (also called environmentally conscious design, eco-design, etc.) is the philosophy of designing physical objects, the built environment, and services to comply with the principles of ecological sustainability ...
of pools.
Other equipment
Diversions to electronic oxidation systems, ionization systems, microbe disinfection with ultra-violet lamp systems, and "Tri-Chlor Feeders" are other auxiliary systems for swimming pool sanitation - as well as solar panel
A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...
s - and are in most cases required to be placed after the filtration equipment, often the last items being placed before the water is returned to the pool.
Other features
Recreation amenities
Features that are part of the water circulation system can extend treatment capacity needs for sizing calculations and can include: artificial stream
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...
s and waterfall
A waterfall is any point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge
of a tabular iceberg or ice shelf.
Waterfalls can be formed in seve ...
s, in-pool fountain
A fountain, from the Latin "fons" ( genitive "fontis"), meaning source or spring, is a decorative reservoir used for discharging water. It is also a structure that jets water into the air for a decorative or dramatic effect.
Fountains were o ...
s, integrated hot tub
A hot tub is a large tub full of water used for hydrotherapy, relaxation or pleasure. Some have powerful jets for massage purposes. Hot tubs are sometimes also known as "spas" or by the trade name Jacuzzi. Hot tubs may be located outdoors or ...
s and spas, water slide
A water slide (also referred to as a flume, water chute, or hydroslide) is a type of Playground slide, slide designed for warm-weather or indoor recreational use at swimming pools or water parks. Water slides differ in their riding method and ...
s and sluices, artificial "pebble beaches", submerged seating as bench-ledges or as "stools" at in-pool bars, plunge pool
A plunge pool (or plunge basin or waterfall lake) is a deep depression in a stream bed at the base of a waterfall or Shut-in (river), shut-in. It is created by the erosion, erosional forces of cascading water on the rocks at the formation's bas ...
s, and shallow children's wading pools.
See also
* Automated pool cleaners
* Copper ion swimming pool system
* Fountain
A fountain, from the Latin "fons" ( genitive "fontis"), meaning source or spring, is a decorative reservoir used for discharging water. It is also a structure that jets water into the air for a decorative or dramatic effect.
Fountains were o ...
* Reflecting pool
A reflecting pool, also called a reflection pool, is a water feature found in gardens, parks and memorial sites. It usually consists of a shallow pool of water with a reflective surface, undisturbed by fountain jets.
Design
Reflecting pools are o ...
* Respiratory risks of indoor swimming pools
* Water purification
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for hu ...
References
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Swimming pools
Swimming pool equipment
Water filters
Water treatment
Water technology
da:Filter (vand)