What pool water should read, and why the states differ

Three pages, three readings

Each row below is one health page, and each figure is that page's own. Where a page gives no figure for something, the cell says so rather than borrowing another state's number.

From SA Health, Queensland Health on rural properties, Queensland Health on spa pools, the Better Health Channel.

Which page applies where

None of these is a national figure. Each was written by one state's own health department for its own readers: SA Health's page for a pool at home in South Australia, Queensland Health's two pages for a pool on a rural property and for a private spa in Queensland, and the Better Health Channel's as a summary for a domestic pool in Victoria. The page for your own state is the one to keep; another state's number is not a stand-in for it.

The disagreement that is easiest to see is the chlorine figure. SA Health gives one range, with no temperature written into it: free residual chlorine maintained at 1.0 to 3.0 mg/L, with the ideal level 2 mg/L. Queensland Health's rural page writes the temperature into the number instead. "In outdoor pools, free chlorine levels (the amount of chlorine that remains in the water as a residual and is available to destroy any new germs) of 2mg/L should be maintained if the temperature is less than 26°C", it says, and "Where temperatures exceed 26°C, 3mg/L free chlorine should be maintained." On the pH the three are closer: Queensland Health's rural page says "The ideal pH level should be between 7 and 7.6", the Better Health Channel says to aim for a pH between 7 and 7.6, and SA Health keeps a narrower band, 7.2 to 7.6, so that the chlorine works efficiently.

Queensland Health's two pages do not even agree with each other, and the reason is written at the top of each. One is a guide to maintaining a private spa pool, and the other is a page about water on rural properties with a section for domestic swimming pool water quality. The spa page says "The pH of the water in your spa pool should be maintained between 7.2 and 7.8" and "The ideal pH is 7.5", which is a narrower and higher band than the 7 to 7.6 its other page gives an outdoor pool.

The rest of the readings

pH and chlorine are not the whole of it. The same pages give numbers for the things that hold the pH steady and protect the pool's own surfaces.

• Stabiliser. Cyanuric acid can be added to a pool in direct sunlight to reduce the amount of chlorine consumed, SA Health's page says, and "It should be maintained at a level of at least 30 mg/L and no more than 50 mg/L." The Better Health Channel says a chlorine stabiliser is what extends the chlorine's half-life, and prints no number for it.
• Total alkalinity. "Alkalinity is a measure of how resistant the water in your spa is to changes in pH", Queensland Health's spa page says, and "Water with a low alkalinity will be very susceptible to changes in pH." SA Health keeps a pool's total alkalinity in the range of 60 to 200 mg/L, checked at least once a week, and the spa page keeps a spa's between 80 and 200mg/L. The Better Health Channel adds that total alkalinity and pH are interconnected, so lifting one can lift the other.
• Calcium hardness. This is the amount of the mineral calcium dissolved in the water. SA Health keeps it in the ideal range of 150 to 400 mg/L, checked once a week to prevent scale formation. The Better Health Channel says calcium that is too low will deteriorate pool surfaces, while too much leaves a scum or scale on surfaces and equipment.
• Temperature, if the pool is heated. SA Health says that for heated pools the temperature should be checked regularly and maintained at a comfortable 26 to 30 degrees Celsius, and that a continuously heated pool will require continuous disinfection.

Why these numbers matter is written on the same pages. "The pH of the water in your spa is important because it affects the effectiveness of the disinfectant you use", the spa page says, so "it is therefore essential that the right pH is maintained at all times." On the outdoor pool its other page adds a consequence a swimmer can feel: "Levels above 8 increase the risk of skin rashes and levels lower than 7 can sting eyes." The Better Health Channel puts the same two effects in its own words, and adds that total alkalinity that is too low can make the pH balance unstable.

Testing, and how often the pages say to do it

The four pages set four rhythms, and each one is written for the pool it describes. SA Health's page says it is important to test the water before use and at least once every day for pH and chlorine concentration, and that the other parameters it lists should be measured at least weekly. The Better Health Channel says to check pH and chlorine levels daily, and that the test should preferably be done before the first swim of the day, so that water quality that altered overnight is caught before anyone is in the water. Queensland Health's rural page sets the floor rather than the ceiling: "As a minimum, pH and chlorine levels should be checked weekly." Its spa page asks for more, because a spa is smaller and warmer: "Disinfectant levels should be tested prior to use and at least three times a week", and "Both pH and alkalinity should be tested prior to use and at least three times a week during use."

Three of the four put the reading before the swim; Queensland Health's rural page sets only a weekly minimum. SA Health also says to use a reliable pool water test kit, and its page notes that kits can be purchased from swimming pool shops, some supermarkets, hardware and major department stores.

A strong chlorine smell means the opposite of what most people think

Two of the pages correct the same belief, and this is the reading a person is most likely to get wrong. Queensland Health's rural page states it in full: "If there is a strong smell of chlorine from your pool, contrary to popular belief, it means that there is not enough chlorine in the pool and chloramines are forming which can irritate the eyes and skin." The Better Health Channel's page says the same thing from the other end: it is too little chlorine, not too much, that causes the smell, because a low chlorine level lets chloramine compounds form, and those compounds are what carry the smell and cause the irritation. Its advice is to check the chlorine level, because the answer may be to add more rather than less.

What the water can carry, and when not to swim

The readings matter because of what the water carries when they slip. Poorly maintained swimming pools can create serious health risks for users, SA Health's page says. Contact with water contaminated with microorganisms may lead to infections of the skin, ears, eyes, central nervous system or digestive system, and the organisms arrive from humans, animals and birds and the environment around the pool. Queensland Health's rural page puts the everyday version of it plainly: "If the water is not properly maintained bacteria, viruses and treatment chemicals may build up and cause health problems such as upset stomachs, rashes and ear, nose and throat infections." The Better Health Channel says the microbes a domestic pool can carry include bacteria, viruses and protozoa, and that they can cause gastroenteritis, ear, nose and throat infections. Queensland Health's spa page adds who is most exposed to them: "The very young, the elderly and the immunocompromised are at particular risk of contracting these diseases."

There is one rule about people rather than water, and the two pages that give it use two different clocks. Queensland Health's rural page says "Users who have suffered diarrhoea or upset stomach in the past 48 hours should not enter the water to prevent spreading illness", and that someone diagnosed as suffering cryptosporidiosis should stay out of the water for two weeks after the diarrhoea has stopped. SA Health's page puts the same two weeks on a household member diagnosed with Cryptosporidium infection, counted from the point at which all symptoms have stopped.

SA Health's page also lists the states the water itself can be in where it should not be swum in at all. Under its heading for when domestic pools should not be used, it names a disinfectant level or pH outside the recommended range or water that is dirty or cloudy, water that has been heavily contaminated, and recirculation pumps and filters that are not operating properly.

Algae, read as a reading

In pools disinfected with chlorine, "the presence of algae is an indicator that free chlorine is not being properly maintained", SA Health's page says, and where algae is present the disinfectant and pH levels should be brought back within the recommended range. The Better Health Channel describes algae as single-celled organisms that multiply fast and can turn a pool green within a few hours.

What this has to do with cleaning a pool

Everything above is a reading, and a reading is only as good as the water it is taken from. Cleaning a pool, in the sense this circuit uses the phrase, is keeping the water moving through the filter and keeping these figures inside the ranges their own state's page gives: the water is read as often as its own state's page asks, the filter runs, and the chemicals go in on the way round. The next guide follows the water out of the pool at the skimmer, where the cleaning starts and where the danger is.