Swimming pool sanitation refers to methods for ensuring healthy conditions in swimming pools, lap pools, hot tubs, plunge pools, and similar recreational water venues. Proper sanitation is needed to maintain the visual clarity of water and to prevent the transmission of infectious diseases.
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 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 and bromine 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[13] whereas bromine-releasing compounds have found heightened popularity in spas and hot tubs.[14] Both are members of the halogen family 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 exhibit strong oxidizer action of undesired contaminants.
Swimming pools can be disinfected with a variety of chlorine-releasing compounds. The most basic of these compounds is elemental chlorine gas (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 commonly known as liquid bleach or simply bleach, calcium hypochlorite and lithium hypochlorite. Chlorine residuals from elemental chlorine and inorganic chlorine-releasing compounds break down rapidly in sunlight. 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 — a granular stabilizing agent capable of extending the active chlorine residual half-life (t½) by four to six fold.[15] 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.
Chlorine reacting with urea in urine and other nitrogen-containing wastes from bathers can produce chloramines. 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 “super-chlorinate” (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.”
Other methods
Conditions sometimes exist in heavily-used commercial and/or public swimming pools whereby supplemental oxidation is warranted. In these instances Advanced Oxidation Processes (AOPs) can be employed whereby water contaminants are oxidized by one or more of four different precursors: ozone, hydrogen peroxide, oxygen, and air in combination with UV radiation and in some instances a catalyst such as titanium dioxide (TiO2). These AOPs react with water (H2O) to produce powerful oxidants such as hydroxyl radical (OH·), singlet oxygen (O) and molecular oxygen (O2).[16]
Water pumps
An electrically operated water pump is the prime motivator in recirculating the water from the pool. Water is forced through a filter and then returned to the pool. A typical pool pump uses 500 watts to 2,000 watts. Commercial and public pool pumps usually run 24 hours a day for the entire operating season of the pool. Residential pool pumps are typical 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 people run for between 6 hours and 12 hours in summer with the pump being controlled by an electronic timer. Commercial pools require a minimum 4 hour circulation of the total water volume. Some use of solar panel generation power for the pumps is done in the Southwestern United States, along with Solar hot water panel pool water heaters.
Some pool pumps have two motor speeds to reduce power consumption at times when full power is not needed. Other pump manufacturers (typically Italian or other European) have redesigned their units to use a smaller electric motor with heavier windings, therefore consuming less energy, to power a larger pump impeller. Variable-speed pumps reduce power consumption even more. Popular in the United States, these pumps run slowly 24 hours a day. The slow speed typically cleans better because smaller particles can be filtered. At the slow speed, minimal resistance in the pipes reduces the energy needed to move the water. [17]
Pool pumps typically are “self priming”: they may be positioned above the mean water level of the pool yet still start up and function after a timed rest period. Pumps that do not “self prime” are termed “flooded suction” and must be gravity fed by the pump by being located below the mean level of the pool water.
Most pool pumps available today incorporate a small filter basket termed a “hair and lint strainer” or “lint pot” 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 filter is typically placed in line immediately after the water pump. The filter typically contains a media 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 to 24 to the inch). A pressure fed sand filter is termed a ‘High Rate’ sand filter, and will generally filter turbid water down to 10 micrometers in size.[18] The rapid sand filter 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 are 1 ton sand per 100,000 liters water.
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) 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 type 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 to help filter out contaminants. Commonly referred to as ‘D.E.’ filters, they exhibit superior filtration capabilities.[19] Often a D.E. filter will trap water-borne 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.
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 50 to 150 square feet (14 m2) 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 goes into the aquifer.
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 pool filtration system as described (above) is termed a “consecutive dilution” system, as a constant and consecutive stream of fresh, chlorinated, and filtered water is being continually returned to the pool as part of a process that could ultimately result in a pool with 100% newly introduced fresh water over a period of time. Of course this goal is never achieved, as there is also a constant stream of new contaminants entering the pool as subsequent sections of this page will indicate.
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. On lifting the lid you will see water being drawn from the pool (if the pool water pump is operational), over a floating weir (operating from a vertical position to 90 degrees 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 and other floating debris.
The aperture visible from the pool side is typically 1′ 0″ wide by 6″ high, which intersects the water midway though 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.
Perimeter Overflow channels
An overflow channel is a gutter that surrounds the pool, covered by a removable grille. Surface water flows over the edge of the pool and runs by gravity to the filtration plant, usually via a catchment and top-up tank. Often the exterior pool wall is higher than the overflow channel, eliminating the possibility of pool water overflowing onto the adjacent pool surround. Other designs may not have this feature, relying instead on a wider drainage system to trap any overflowing water.
Overflow channels allow faster turnover of the surface water than is possible with simple weir skimmers, which is why they are commonly found in public pools. They can also be attractive designs, particularly when transformed into a total Infinity edge pool. This design has been used to great effect in prize winning contemporary home design, notably in Southern California and the surrounding desert states.
Pool recirculation
The final link in the pool recirculation system: skimmer-pump-filter-returns are the water returns. Typically these are referred to as “eyeballs” as they incorporate a swiveling nozzle that can be locked down to point in the desired direction and are reminiscent of a swiveling human eyeball. The directional adjustment is usually a 360 degree radius circle of 45 degrees away from the pool wall. Most home pools would incorporate at least two such “eyeballs”.
One recent development in skimmers was the 1970s “Aquagenie(TM)” which differs considerably operationally from conventional skimmers—most of which are quite similar in operation, if not appearance—by both drawing the pool water and returning it to the same location through a submerged slot which diverts the water downwards and in a wide fan shape. The concept incorporates a reservoir system to contain saturated trichor tablets which the resulting high strength chlorinated water dribbles back into the recirculation system, so it doubles up as a chlorine feeder as well as a normal skimmer. Arguably an “improvement” in skimmer design, patents on the device expired in 2003 and the system is now available from several US manufacturers.
Heaters
Other equipment which may be optioned in the recirculation system include pool water heaters. They can be heat pumps, natural gas or propane gas heaters, electric heaters, and Solar hot water panel heaters – increasingly used in sustainable design 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 panels; are in most cases required to be placed after the filtration equipment, and are the last items before the water is returned to the pool.
Other features
Equipment enclosure
Most swimming pool installations incorporate an outdoor structure designed to house the pool filtration equipment; as a protective measure against premature deterioration from sunlight and rain; and as motor noise-sound insulation for the pool users and neighboring properties. Typically, these structures range in size from a simple flip-lid three-sided sound-insulated box set against a convenient house wall, the lid being constructed on a 15 to 20 degree slope and the interior large enough to hold the filter plant, pump, and whatever chlorination system has been included.
Some structures are, in addition to a separate sound-proofed pool equipment location, a Pool House (Pool Cabana – “Pool Shed”) with a bathroom, shower, changing, and storage area; and sometimes a full-size building with an: entertainment and recreation room, a small kitchen, and “guest house” accommodations. . Consistent vigilance for the safety of young children in and around the pool, often by a designated adult, is important where social distraction is possible.
Recreation amenities
Features that are part of the water circulation system can extend treatment capacity needs for sizing calculations and can include: artificial streams and waterfalls, in-pool fountains, integrated hot tubs and spas, water slides and sluices, artificial “pebble beaches,” submerged seating as bench-ledges or as”stools” at in-pool bars, plunge pools, and shallow children’s wading pools.
Landscape designers often integrate the pool and its amenities and surrounding decking with the property’s gardens and the residence. Outdoor kitchens, barbecues and pizza ovens, walkways and patios, plantings, shade structures, garden furniture and outdoor fireplaces, and landscape lighting in the pool and the garden, all can expand the recreational and aesthetic possibilities of a well sanitized sparkling pool.