Pools - Water Quality Factsheet .au



|Introduction |

Most concerns about swimming relate to drowning, diving injuries, and sunburn. Less concern is paid to getting ill from contaminated water. Be ahead of the crowd by learning more about recreational water illnesses (RWIs) and how to protect yourself and your family when swimming. Protecting swimmers and their families from RWIs is the reason that chlorine and pH levels should be regularly checked.

|What does chlorine do? |

Chlorine kills germs in pools—but it takes time to work. Therefore, it’s important to make sure chlorine levels are always at the recommended levels. Learning how to test your pool water will allow you to identify the chlorine residual and demand in pool water. More frequent testing is needed if there is heavy bather load. Listed below are some helpful definitions that will assist you in understanding the terms and tasks of applying chlorine-based sanitizers.

• Free available chlorine (FAC). The portion of the total chlorine remaining in chlorinated water that has not reacted with contaminants. Make sure your test kit can measure FAC; many only test for total chlorine.

• Combined available chlorine (CAC) or chloramines. The portion of chlorine in the water that has reacted and combine with ammonia, nitrogen containing contaminants and other organics such as perspiration, urine and other swimmer waste. Some chloramines can cause eye irritation and chlorine odours.

• Total chlorine. The sum of both the free available and combined chlorines.

• Forms of chlorine commonly used in pools. Sodium hypochlorite (liquid bleach), calcium hypochlorite (granular or tablet), chlorine gas, chlorinated isocyanurates.

• Parts per million (ppm). Measurement that indicates the parts of a substance, such as chlorine, by weight in relation to one million parts by volume of pool water.

• Shock treatment. The practice of adding significant amounts of an oxidizing chemical to water to destroy ammonia, nitrogen-containing and organic contaminants. Adding chlorine as a shock treatment can also control algae and bacteria, but read the label to make sure that your product can do this.

Carefully read and follow the manufacturer’s instructions printed on the chlorine treatment package. Test the water regularly – it’s a simple process to use a test kit. You want to maintain water balance by measuring:

• Free available chlorine (FAC), which should never fall below 1.0ppm.

• Total chlorine, to ensure that combine available chlorine (CAC) levels are less than 0.2ppm.

• The pH level to keep it between 7.2 and 7.8, indicating that the chorine is working effectively.

• Total alkalinity to make sure that pH level stay steady.

• Calcium hardness to protect pool surfaces from corrosion.

|Why does chlorine need to be tested regularly? |

All sorts of things can reduce chlorine levels in pool water. Some examples are sunlight, air, debris and material from swimmer’s bodies. That’s why the levels must be routinely measured. However, the time it takes for chlorine to work is also affected by the other part of the disinfection team, pH.

|Why is pH important? |

Two reasons, first, the germ-killing power of chlorine varies with pH level. As pH goes up, the ability of chlorine to kill germs goes down. Secondly, a swimmer’s body has a pH between 7.2 and 7.8, so if the pool water isn’t kept in this range then swimmers will start to feel irritation of their eyes and skin. Keeping the pH in this range will balance chlorine’s germ-killing power while minimizing skin and eye irritation.

|Shock Treatment |

Contrary to what most people think, a strong chlorine smell is not an indication of too much chlorine in the pool but actually a red flag that a super dose of chlorine (shock treatment) may be required to correct the problem.

Shock treatment adds a larger than normal amount of oxidizing chemicals to pool water. This additional dose destroys organic contaminants and oxidizes ammonia and nitrogen compounds to rid the area of irritating chloramine odour and, if chlorine is used for the purpose, to sanitize the water. Many chlorine shock products also provide usage instructions for destroying algae and bacteria, which can be an added benefit. Shocking should be done with the pump and filter operating, but after sundown to avoid the loss of chlorine to the sun’s ultraviolet rays.

Superchlorination is another term that is sometimes used for shock treatment with chlorine products when 5 or more ppm of FAC is added. This mode of shock treatment – in addition to oxidizing undesired wastes – is used to rid the pool of algae and bacteria that might be concealed in filters and hard-to-sanitize areas. Superchlorination also eradicates chloramine odour. Super chlorination should achieve so-called breakpoint chlorination - when there is enough extra chlorine to consume the irritating chloramines and the test for free available chlorine and total chlorine will give the same value.

This fact sheet was initially developed by Gold Coast City Council and is recognised and adopted by participating Queensland Councils.

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