I think the answer to your question is about 3-6 days. The problem is that the chlorine that you need to keep the bacteria in check is used up more quickly as the temperature rises, the activity increases, and as sweat and other body stuff is put into the pool.
It takes a lot of chemicals to make pool water safe for swimming. Untreated water can accumulate harmful Escherichia coli and Salmonella bacteria and protozoans such as Cryptosporidium parvum and Giardia lamblia.
The ideal level of free chlorine in the swimming pool is 2 to 4 ppm. 1 to 5 ppm is acceptable and 9 ppm is on the high side. 9 ppm would likely be safe to swim, but could be more of an irritant. Ideally, the level would be alllowed to come down to 5 ppm before swimmers are allowed to swim.
CDC recommends pH 7.2–7.8 and a free chlorine concentration of at least 1 ppm in pools and at least 3 ppm in hot tubs/spas.
Warmer air will cause the chlorine to evaporate more rapidly. If you decide to place the water in a jug that's left open in the refrigerator, the chlorine should evaporate completely within 24 hours. For quicker evaporation times, leave the water at room temperature.
Even from a health standpoint, it is simply not safe to operate a pool without some added “chemicals” to combat bacteria and contaminants in the water. A pool without chemicals is the perfect breeding ground for bacteria, viruses, and parasites.
When water sits in place for too long and is exposed to an unsterile environment, it becomes contaminated. Swimming in stagnant water can expose you to serious health hazards. Stagnant water becomes a breeding ground for parasites, mold, and bacteria.
There are alternatives to chlorine including bromine, ionizers, and ozonators, though with each you'll still need to use some chlorine. A fourth alternative is PHMB, which doesn't require the use of any chlorine.
Using swimming pool salt instead of chlorine delivers greater swimming comfort: Swimming pool salt does not give off an unpleasant odour as chlorine does. It is much less harsh on hair and skin. It does not cause your eyes to sting.
“It's important to change the paddling pool water every day – drain it and let it dry at the end of the day and use an anti-bacterial spray to kill any germs so it is safe to use the next day.”
In fact, bleach is often recommended for emergency water disinfection, so reasoning suggests it can work well in a kiddie pool. However, not much bleach is required to properly sanitize a given amount of water.
Why is chlorine added to swimming pools? Chlorine is added to the water to kill germs. When it is added to a swimming pool, it forms a weak acid called hypochlorous acid that kills bacteria like salmonella and E. coli, as well as germs that cause viruses such as diarrhea and swimmer's ear.
So free chlorine is the chlorine you want in your pool, but sunlight can affect its ability to work. The chlorine breaks down and is released into the atmosphere when the sun's UV rays hit it. On a day with full sun, it only takes around 2 hours for 90% of your pool's chlorine to be broken down.
Yes, boiling water for 15 minutes is one way to release all the chlorine from tap water. At room temperature, chlorine gas weighs less than air and will naturally evaporate off without boiling. Heating up water to a boil will speed up the chlorine removal process.
Simple aeration can remove the chlorinated compounds from water. However, from a cost perspective, it is much cheaper to use chemicals for the dechlorination. The reason is that an aeration system takes a considerable amount of time and energy to remove the chlorine.
Do not use Epsom salt in an ordinary, chlorinated pool. Epsom salt will quickly corrode traditional filters and can cause other pool problems that will require the intervention of a professional.
Is a salt water pool better than a chlorine pool? In our professional opinion, YES! Salt water pools are generally lower in chlorine. The chlorine found in saltwater pools are naturally produced from salt, rather than adding harsh liquid chlorine (a.k.a bleach).
It's recommended to wait at least 20 minutes to swim after adding salt to your pool. If you're adding calcium chloride to your pool water, it's recommended to wait two to four hours before swimming again.
Short answer: yes. Longer answer: it depends on the formulation. The label on every bleach bottle should tell you the ratio of sodium hypochlorite (and available chlorine) in the bottle to everything else. A higher percentage is generally better, as you'll need to use less bleach to treat your pool.