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.
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.
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.
Swimming pools need chlorine to keep the water clean and safe to swim in. Chlorine helps keep water clean by preventing the growth of algae. It keeps your pool water safe by attacking and neutralizing harmful bacteria and microorganisms. The magic of chlorine is in a simple chemical reaction.
We're probably all familiar with at least one of the common side-effects of swimming: sore eyes, skin irritations, fading swimming costumes, and that lovely smell that lingers until you've had a good shower. But chlorine itself, when used at the recommended low levels, is perfectly safe.
What can happen if you go into a pool too soon after it's been shocked? There are a few potential issues. "Chlorine will react with water to produce an acid," Alan says. "The effects will be different depending on whether chlorine is inhaled or whether there is skin or eye contact."
If the chemicals used to kill germs (chlorine or bromine) in pools, hot tubs, and water playgrounds are not kept at the right level, these germs can multiply and make swimmers sick.
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.
Statistically, a pool without chlorine is more likely to make you sick because of the possibility of being exposed to the things not contained or killed by chlorine. Remember, your skin is porous, so microscopic impurities can pass through. A pool sans chlorine is akin to a big puddle of murky water.
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.
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.
“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.”
After you shock the pool — As soon as your chlorine levels reach 5 ppm or lower, it's officially safe to swim. Depending on the type of shock used, as well as the amount used, it can take anywhere from 24 hours or even up to a couple of days.
Chlorine, either solid or liquid, is a pesticide used in pools to destroy germs, including those from feces, urine, saliva and other substances. But excessive exposure to chlorine can cause sickness and injuries, including rashes, coughing, nose or throat pain, eye irritation and bouts of asthma, health experts warn.
It is a good idea to wait at least 20 minutes after adding the water balancing chemicals. After 24 hours, it is safe to swim if you have a chlorine level of at least 5 parts per million. ...
While the quart or so of water that was setting in the hose may have some chemical contaminants in it, by the time that is diluted into thousands of gallons of water, it's of no concern. That is of course assuming that your swimming pool is not your primary source of all drinking water.
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.
Pros of Saltwater Pools
They're gentler on the skin, with less irritation to the eyes, hair and swimsuits. The water has a softer, silkier feel to it compared to chlorine water. They have lower maintenance costs than chlorine pools. There's no need to store harmful chemicals.
Yes you can turn your pool pump off for a week. You can turn it off for a month, but there are consequences. The pool will get dirty—no pump, no filtering. The chemicals will not circulate and the water could start turning a nice shade of green as algae forms.
If ground water is not a problem a pool can be left empty for weeks or even months as long the hydrostatic relief in the bottom of the pool is open and functioning. If the time frame of the pool being empty gets into freezing weather there is real risk of freeze-thaw damage to surface of the pool.