How Long Can a Pool Last Without Chemicals?

Having a pool with completely untreated water seems very appealing to many people. After all, natural water doesn’t have any chlorine or other chemicals, so why should we not try to mimic that? However, there are vast differences between pool water and water in nature; untreated pool water is usually a perfect breeding ground for bacteria, which can negatively affect your health. 

Pool water cannot last long without chemicals. In the best-case scenario, it will last around three to six days before becoming stagnant and dangerous due to the concentration of bacteria and algae. Therefore, not treating your pool water with chlorine or similar chemicals can be hazardous and is not advised. 

In this article, I’ll go over how long pools can last without being treated and why you need to treat them in the first place. I’ll also discuss what can happen to your water if untreated and what dangers it might bring. 

Pools need chemicals to stay safe

How Long Before Pool Water Becomes Dangerous?

Pool water starts becoming dangerous after three to six days due to the buildup of bacteria and algae. So even though the water might still look clean and inviting, it will probably not be safe for swimming. 

The longer you leave it untreated, the worse it will look. After two weeks, you’ll notice green scum from the algae forming on the water surface, which should be an obvious sign that the water is dangerous. 

Leave it even longer, and it will turn into something closer to a toxic swamp than a pool. The layer of algae will just get thicker, you’ll probably get some plant growth, and soon enough, you might get a nice colony of mosquitoes to keep you company. You don’t want this happening, do you? 

Why Does Pool Water Become Dangerous?

Pool water becomes dangerous because warm and wet surfaces are the perfect breeding ground for bacteria, parasites, viruses, and algae. Pools, which are small, stagnant bodies of water, are very conducive to their proliferation and will enable them to multiply very quickly. 

Just to put things into perspective: bacteria can double in numbers every four to twenty minutes, which makes them some of the fastest-reproducing organisms in the world. You can only imagine how many of them you can get after a few days of not getting rid of them. 

Algae are very similar in this regard. Algae generally double in size every 24 hours. Some of them can even double every three and a half hours in their peak reproductive season. Combine that with the bacteria, viruses, and other dangerous microorganisms, and you’ve got a recipe for a disaster. 

Are Pool Chemicals a Cause for Concern? 

Pool chemicals are not a cause for concern. If pool chemicals, like chlorine, are used in appropriate quantities, they don’t cause any problems. In fact, chlorine keeps your pool water safe and prevents more problems than it causes. 

What’s more, you probably drink some amount of chlorine every day. Pretty much all of our tap water has to be treated with chlorine to render it safe for consumption. If you can drink it, why should you not swim in it?

The chlorine level deemed safe in drinking water is up to 4 ppm (parts per million), while the minimum amount required in commercial swimming pools is 1.5 ppm. We can see that the amount of chlorine in your typical pool is too low to cause you any harm.  

For more information on pool chemicals, check out The Beginner’s Guide to Pool Water Chemistry.

Are There Any Risks to Using Chlorine?

There are risks to using chlorine. If the amount of chlorine exceeds what’s recommended, it can lead to minor health issues (more so in children than adults), especially if they’re prone to health problems. However, the exposure to chlorine in your pool isn’t significant enough to cause problems.

Chlorine can irritate your

  • Eyes
  • Skin
  • Upper respiratory tract

In spite of this, most cases of chlorine poisoning happen outside of pools. They can occur after contact with certain cleaning products, rather than with pool water. Unless, of course, you literally drink the water treated with chlorine.

Pool Test Kit

Are There Any Alternatives to Chlorine? 

There are no alternatives to using chlorine to keep your pool clean. There are some other options you can choose from, but they have to be combined with at least a residual amount of chlorine to be useful. They also don’t come without any risks. 

Therefore, if you’re hell-bent on not using chlorine, the only option would be to replace your pool water every time you go swimming. This, of course, is extremely wasteful and would hike up your water bills in the blink of an eye.

Plus, you would have to scrub very hard to get rid of dirt and algae. This means that you would have to invest a lot of time in cleaning the pool on top of the water costs. So, this is not really an option for anyone. 

Some options you can look into include: 

  • Advanced Oxidation Process systems
  • Ozone pool systems
  • UV pool systems

Advanced Oxidation Process systems, or AOP for short, kill bacteria by creating hydroxyl radicals. They can achieve a great degree of water clarity, but they require a pump to work 24/7 to process the water. 

Ozone pool systems use ozone to kill contaminants. However, ozone is a toxic gas, so it can only purify the water in the pipes, not in the pool itself. On top of that, it takes weeks for it to fully ozonate the water. 

UV pool systems use UV lights to kill bacteria and other contaminants. However, they require a lot of energy to operate, so they might not be the best option if you’re looking for something that’s affordable. 

Final Thoughts

Chemicals, such as chlorine, make your pool water safe from contaminants and pose very little risk. This is especially true when it comes to your backyard pool. Therefore, you should not leave your pool water untreated for more than three to six days. Otherwise, it will become too dangerous to swim in, and you’ll have to replace it entirely.