Poorly maintained swimming pools can create serious health risks for users. Humans, animals and the environment can contaminate pools with infectious organisms. In most cases these organisms cause mild illness, but some infections can be serious or potentially fatal.
Pools that are poorly maintained can create potential health risks for users. Harmful bacteria and viruses must be killed quickly to prevent user infection. Contaminants such as sunscreen, skin and hair should also be treated or removed.
Algae must also be controlled. Contact with water contaminated with microorganisms may lead to infections of the skin, ears, eyes, central nervous system or digestive system. Dangerous organisms can be introduced from humans, animals and birds and the environment. Most cause mild disease, but some infections can be serious or fatal.
Pool safety is also important. Children should always be supervised and pools securely fenced. Domestic pool owners should be trained to perform cardiopulmonary resuscitation (CPR).
Only treated mains water from a domestic water supply should be used to fill a pool. However, this water may have unsuitable pH or mineral levels that may interfere with disinfection and damage your pool and equipment with stains, scale and corrosion. Therefore, pool water will usually require regular testing and chemical treatment.
Seek advice from an environmental health officer at the local council if another water source is to be used.
Water remains in a pool for long periods of time, so it must be treated to keep it clean and safe. Proper disinfection and filtration of pool water kills harmful microorganisms and removes body fats, oils, soil and other contaminants.
Pool water must be regularly circulated and filtered. If the pool filter doesn’t operate properly, the chemicals added to keep the pool disinfected and clean will not be effective.
Common filter types include sand filters, diatomaceous earth and cartridge filters.
The filter system should be able to completely filter a volume of water equivalent to the volume of all the water in the pool within six to eight hours. The filtration system should operate continuously when a pool is being used and for at least one hour afterwards.
Filters should be cleaned regularly to ensure they are operating at maximum efficiency.
It is important to test the water before use and at least once every day for pH and chlorine (or other disinfectant) concentration.
More frequent testing should be done in hot sunny weather or when the pool is being used by many people, so that changes in water quality are detected before problems develop. Other parameters (see below) should be measured at least weekly.
Reliable pool water test kits should be used - kits can be purchased from swimming pool shops, some supermarkets, hardware and major department stores.
The following parameters should be adjusted as necessary.
Commercially available disinfectants for domestic swimming pools should be used. Chlorine is the most common, but bromine, ozone, ultraviolet (UV) irradiation and ionising systems may be used.
If chlorine or bromine are not the main disinfecting agents, a small amount of >chlorine or another oxidising agent should be added to maintain residual disinfection activity in the water. Consult a pool supplier for more information.
The chlorine in the water that can effectively kill bacteria is called ‘free residual chlorine’. If chlorine is used, the free residual chlorine concentration in your pool should be maintained at 1.0 to 3.0 mg/L. The ideal level is 2 mg/L.
When a pool is not in use, a method such as a floating immersion dispenser should be used to disinfect the pool water at all times.
After a pool is heavily used, after a rainstorm, or if a pool has been poorly maintained it may require ‘shock dosing’ to bring it back to a safe standard for use.
Shock dosing instructions:
Add sufficient chlorine to the pool water to achieve 10 mg/L residual free chlorine. For example, add 200mL of liquid sodium hypochlorite (12.5% available chlorine) or 30g of granular calcium hypochlorite per 1000 litres of water.
Maintain 10 mg/L free residual chlorine for at least one hour.
Operate the pump and filter at all times during shock dosing.
Other products may be available for this purpose. Consult with your pool supplier.
Do not use the swimming pool until free residual chlorine falls to 4 mg/L. This may require leaving the pool overnight.
Salt pool chlorinators
One method of chlorinating a pool is to use a salt pool chlorinator. A measured quantity of salt is dissolved in pool water. As the salt water passes through a chlorine generating cell, it produces chlorine. Refer to your salt chlorinator’s operation instructions for specific details.
Disinfecting against Cryptosporidium infection
If someone in your household has been diagnosed with Cryptosporidium infection, they should not use a swimming pool two weeks after all symptoms have stopped. If an infected person has used your pool during the infectious period, you should disinfect the pool to prevent the spread of infection to others.
If you are not confident that you can successfully disinfect the pool on your own, contact a pool maintenance company (fees apply). When using chlorine to disinfect a pool against Cryptosporidium, the following process is recommended:
add sufficient chlorine to the water to achieve 10mg/L free chlorine residual
ensure 10mg/L free chlorine residual is maintained continuously for at least 25.5 hours (you will need to add more chlorine periodically)
operate the pump and filter at all times during disinfection
backwash the filter thoroughly after completing the disinfection process.
It may be quicker, easier and more cost effective to drain and thoroughly clean a spa rather than undertake the disinfection process.
Caution: After disinfection, do not use the swimming pool or spa until the free chlorine level falls to the normal concentration. This may require leaving the pool unused for another day or two.
To ensure chlorine works efficiently, the pH range must be maintained within 7.2 to 7.6. This is also the ideal pH of water for the comfort of pool users.
Stabiliser (cyanuric acid)
To prevent chlorine from rapidly breaking down in pools exposed to direct sunlight, cyanuric acid can be added to reduce the amount of chlorine consumed. It should be maintained at a level of at least 30 mg/L and no more than 50 mg/L.
Further advice on stabilisers can be obtained from a swimming pool supplier.
Total alkalinity should be checked at least once a week to prevent cloudy water, scale formation, metal corrosion and keep the water comfortable for users.
Total alkalinity should be maintained in the range of 60 to 200 mg/L and adjusted as necessary by using sodium bicarbonate as advised by a swimming pool supplier.
Add small quantities of chemical mixed with water at a time to the pool with the pump and filter operating. Wait 10 to 15 minutes before testing.
To prevent scale formation, calcium hardness should be checked once a week. The ideal range of calcium hardness is 150 to 400 mg/L.
Algae are small organisms that multiply rapidly and can form slimy, green floating material or coat surfaces. They are very common organisms brought in by rain, wind, soil or even on swimwear and cleaning equipment.
Good pool maintenance can prevent algae growth. In pools disinfected with chlorine, the presence of algae is an indicator that free chlorine is not being properly maintained. If algae is present ensure that disinfectant and pH levels are within the recommended range.
Algae can also be controlled by the use of an algaecide, but if algae persist consult your pool supplier.
Topping up the pool
The water in the pool should be topped up regularly using a hand-held hose or bucket. Disinfectant and pH levels should be checked after topping up. All top up water should be added via the skimmer box with the filtration system running.
Water temperature is one of the factors that affect disinfection, so treatment should be adjusted to maintain recommended values. If the pool is continuously heated it will require continuous disinfection. For heated pools, check the temperature regularly and maintain it at a comfortable 26 to 30º Celsius.
All domestic swimming pools need regular cleaning:
remove litter and vacuum the bottom of the pool regularly to remove dirt and debris
scrub the pool walls and surrounding areas regularly to remove debris
clean the pump lint-pot and filter system regularly (daily when using manual dosing)
repair any damaged pool surfaces
keep pipes, filters and motors in good working order.
service all pool equipment according to manufacturer’s directions
ensure all electrical equipment is maintained in good condition
use a pool cover when the pool is not in use to keep dirt, leaves and debris out, to minimise mosquito breeding, and to reduce water loss by evaporation
store, handle and use pool chemicals according to the manufacturer’s instructions
Domestic pools should not be used if:
the disinfectant level and/or pH is not within the recommended range or the pool water is dirty or cloudy
the water has been heavily contaminated
the recirculation pumps and filters are not operating properly.
Fencing and safety
All swimming pools must have a continuous safety barrier maintained by the pool owner that restricts access by young children to the pool. For all the details on fencing your pool, see Pool and spa safety.
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