Safety and Regulation

Important information and guidance published by Australian Health bodies

Consistent disinfection under varying conditions

Water treatment and chemical automation information for swimming pools and spas has been published by many Australian Health bodies and their Fact-sheets could be found over the web. However, the following primary objectives are crucial for the safety of every recreational water environment:

  • Maintaining clean and safe water that meets the bacteriological and physiological requirements of the country/state and local Health Departments,
  • Protecting the equipment from corrosion or scaling caused by the aggressiveness of water and its constituents.

To meet with these objectives and for the convenience of our readers, we’ve gathered some important information and guidance from:

  1. NSW Government/ Health Protection Department
  2. Australian swimming pool and spa associations (SPASA).
  3. World Health Organisation (WHO)

NSW Government, Health Protection Department

NSW Health guidance regarding Swimming pool and spa/ last published in 2013.
Public Swimming Pool and Spa Pool Advisory Document


Clause no.6.3.4. Automatic Controllers
“recently, some oversees manufacturers have developed advanced controllers which are reported to make the most of the benefits of each sensor technology and are capable of combining the inputs of both free chlorine probes, and/or redox (ORP) probes using patented control algorithms. This approach ensures both consistent disinfection under varying water conditions and reliable free chlorine residual levels”.


Clause 6.3.2 Oxidation-reduction potential
“Oxidation-reduction potential (ORP, redox) measures the rate of oxidative disinfection caused by the addition of the effects of all oxidants in the pool water. ORP is determined by using a high quality ORP probe and meter. The unit of measurement of ORP is millivolts (mV)”.

“ORP is an indicator of micro-organism inactivation. Studies on specific micro-organisms have found a direct correlation between increasing ORP and micro-organism inactivation as shown in Graph 6.1. Drinking water is adequately disinfected at an ORP of 650 mV. In swimming pools, an ORP of 700 to 720 mV allows for both a quick disinfection and for breakpoint chlorination (destruction of chloramines) where conditions permit”.


Clause 6.4 Water balancing
“The term ‘chemical water balance’ means that pH, total alkalinity and calcium hardness are within an optimum range to prevent calcium scaling, calcium corrosion and bather discomfort.

Balanced pool water prolongs the life of a pool and its fittings, assists with preventing stains and improves bather comfort”.  Water balance is most significantly affected by:

  • pH
  • Total alkalinity
  • Calcium hardness
  • Temperature


Clause 6.4.2 pH


 “pH is a measure of the hydrogen ion concentration in water or more simply a measure of how acid or alkaline a pool is. The pH scale ranges from 0 to 14, with 7.0 being neutral. A pH below 7.0 indicates acidic conditions and a pH above 7.0 indicates alkaline conditions.

To maintain disinfection levels and bather comfort, pH should be maintained between 7.2-7.6 (maximum 7.8). At a pH below 7.2 there is discomfort to bathers and corrosion to pool equipment. See section 4.4.1 for a discussion on the effect of pH on chlorine disinfection”.



6.4.3 Total alkalinity
“Total alkalinity is a measure of the alkaline salts (bi-carbonates, carbonates and hydroxides) present in water. Total alkalinity prevents large fluctuations in pH, known as pH bounce. To increase total alkalinity, a buffer such as sodium bicarbonate is added to the water; to lower total alkalinity, acid is added. pH will need to be re-adjusted as a change in total alkalinity alters pH. Table 6.1 is an overview of total alkalinity levels”.










6.4.4 Calcium hardness
“Calcium hardness is a measure of the amount of dissolved calcium salts present in the water. Pool water that is very high in calcium hardness can cause scaling of heaters and pool finishes. Pools that have low calcium hardness can cause corrosion of pool equipment and etching of cement and tile grout. Some raw water sources from rural areas are naturally hard (hardness over 250 mg/L CaCO3) making these water sources more suited to treatment using sodium hypochlorite rather than calcium hypochlorite. Similarly, soft waters (hardness under 50 mg/L CaCO3) should be treated with an alkaline disinfectant such as calcium hypochlorite or sodium hypochlorite plus calcium chloride, and a gentle acid such as carbonic acid from carbon dioxide should be used to decrease pH with a gentle buffering effect. A pool consultant should be engaged to determine the most suitable pool treatment system”.


6.4.5 Temperature
“Temperature has an important effect on water balance, mainly because calcium salts become less soluble at higher temperatures. Hence high temperature pools are often subject to scaling as the calcium salts deposit on equipment and pipes. At a lower temperature the water can absorb more calcium which could cause etching of pool surfaces”.


6.4.6 Langelier saturation index
“In order to measure or to give an indication of the solubility of calcium carbonate (CaCO3) in the swimming pool water, the Langelier saturation index (LSI) is used”.

“There are four parameters that need measuring and input into a formula to calculate the index:

  • pH
  • Temperature – temperature factor (TF)
  • Total alkalinity – alkalinity factor (AF)
  • Calcium hardness – calcium factor (CF).

The LSI formula is: pH + TF + AF + CF – 12.1 = LSI where 12.1 is an adjustment constant. The ideal result for the LSI is –0.2 with a range of –0.5 to + 0.5”.


Disinfection of Public Swimming Pools and Spa Pools

“Infections are caused by many pathogenic microorganisms simply known as germs. Disinfection is a process that kills germs, but not their spores, and reduces the risk of disease transmission. Public swimming pools and spa pool must maintain recommended disinfectant, pH and alkalinity levels to minimise the risk of disease transmission.”


“Disinfection is a process which kills germs, but unfortunately not their spores. The aim of disinfection is to reduce the risk of transmission of infections. Disinfection is not an instantaneous process but takes time. The higher the concentration of disinfectant the more rapidly it kills. At the minimum recommended concentrations of chlorine and bromine, the kill time is about one minute or less for most germs.

Most germs are easily controlled by disinfection but Cryptosporidium oocysts and Giardia cysts, which are types of spores, are resistant to disinfectants. Their transmission needs to be controlled by preventing these germs and their spores from entering into pool or spa. There is a separate fact sheet about Cryptosporidium and Giardia.

Disinfectant levels above the recommended minimum concentrations must be present in the pool water at all times. Disinfection must be provided by a disinfectant which leaves an effective residual in the pool that is not harmful to swimmers.”

Suitable disinfectants

“Chlorine and bromine based disinfectants are the only satisfactory pool and spa disinfectants recognised by NSW Health for use in public swimming pools and spa pools. They also oxidise and destroy some organic chemicals which may enter the pool. These disinfectants provide a readily measurable residual in the pool water. Each disinfectant has its advantages and disadvantages and pool operators should consider any disinfectant or disinfectant system carefully before use.”

Dosing of disinfectants (See separate Fact Sheet)

“All public swimming pools and spas must, as a minimum, have continuous metered dosing equipment to continuously dose the disinfectant. Automatic dosing equipment should be used it is important to respond quickly to changes in chlorine demand in busy pools. Dosing systems must be active while the pool or spa is open and for at least one hour before and after the pool is open.

Efficient chlorine pools operate on the chemical process known as breakpoint chlorination which can only be reliably and constantly achieved with dosing equipment (see separate Fact Sheet – Continuous Breakpoint Chlorination).”

Disinfection factors

  • Increasing pH decreases disinfection power so that above pH 7.6, chlorination is ineffective and above pH 8.0, bromination is less effective.
  • Stabiliser (cyanurate) should not exceed 50mg/L as disinfection becomes ineffective and chlorine levels should be increased if stabiliser is used. Stabiliser is not suitable for use with bromination.
  • Pools should be equipped with a circulation system and filters capable of producing clean, clear water. Filtered water is easier to disinfect, reduces contaminants and produces less by-products. Circulation systems should be operated at all times while the pool or spa is open, and for at least one hour before and after the pool is open.

Australian swimming pool and spa associations (SPASA)

(Below some links and Fact Sheets from SPASA in NSW, VIC and QLD).

  • Automatic Control – “Automatic controllers can now monitor and adjust pool chemical balance with a high degree of accuracy”“Conditions in and outside the pool or spa are always changing and that affects the demand for sanitiser and pH balance. On hot, windy days, when the pool or spa is full of people, the demand for sanitiser is far greater than on a cool overcast day with only one person in the pool or spa. Chemical controllers are truly automatic. They are programmed to consistently monitor and maintain chlorine and pH levels at all times whilst the system is running”.


  • Water Balance – “When the chemicals are out of balance, the water will aggressively seek to balance itself by either attacking the pool surface, corroding pool equipment, or forming scale on various surfaces. This can be expensive and it can also inhibit the sanitising process. In simple terms, the pool owner should balance the pool’s pH, its total alkalinity and the calcium hardness”.



  • Sanitizing – “The primary reason for treating pool and spa water with sanitising chemicals is to prevent the growth of bacteria which would make swimmers and bathers sick. These bacteria can cause infections in ears, nose and throat and possibly other more dangerous diseases like Meningitis”. “It is generally accepted that most harmful bacteria will be killed when exposed to a “free chlorine residual” as low as one milligram per litre or, in other words one part per million (ppm). By regularly testing the water and adding the required amount of chlorine to the pool, a residual level of 1.0 or 2.0 ppm is easily maintained.



  • TOTAL ALKALINITY (T.A.) – “This is a measure of bi-carbonates, carbonates and hydroxides in the pool. The Australian Standard recommends a range of 60 to 200 parts per million (ppm). Usually, 120 to 160ppm in swimming pools and 60 to 150ppm in spas is the accepted range, depending on the other balance factors”.


  • CALCIUM HARDNESS – “This is a measure of the amount of dissolved calcium in your pool water. Depending on the other balance factors, the Australian Standard recommends a range of 80 to 500ppm. Both Total Alkalinity and Calcium Hardness need to be in balance”.

World Health Organisation (WHO)

Guidelines for safe recreational water environments, World Health Organisation

The World Health Organisation has published international guidelines for the safety of swimming pools and similar recreational-water environments, including standards for minimizing microbial and chemical hazards: “The oxidation–reduction potential (also known as ORP or redox) can also be used in the operational monitoring of disinfection efficacy. In general terms for swimming pools and similar environments, levels in excess of 720 mV (measured using a silver/ silver chloride electrode) or 680 mV (using a calomel electrode) suggest that the water is in good microbial condition, although it is suggested that appropriate values should be determined on a case-by-case basis.”