How to Lower Chlorine Levels in Pools?

how to lower chlorine in pool

Pool hygiene is maintained by using a balanced amount of chlorine. Certain levels of chlorine are acceptable to keep the pool chemistry intact. However, over-chlorination is a very common problem in pool management. First, let us understand why a pool becomes over-chlorinated, why a higher amount of chlorine is added in the pool, what is the correct level of chlorine that is important for our health.

How Can We Correct Over-chlorination?

It is a very critical task to keep your pool clean and pathogen-free, it’s not as simple as it sounds. Adding the correct amount of chlorine into the pool is of utmost importance. But if there are a lot of organisms built up in the pool over the period, then you will have to shock the water by adding a high concentration of chlorine to combat algae and other bacterias. If the pool was just filled or hasn’t been treated for some time, then shock it first.

Please note that the normal chlorine range is generally between 1.0 ppm to 3.0 ppm (PPM is a unit used to express the diluted concentration of substances) depending upon the level of Cyanuric Acid (CYA) also known as pool/chlorine stabilizer, pool conditioner, etc.

CYA protects chlorine from being consumed by the ultraviolet rays, so if your CYA level dips, the chlorine will be completely gone in no time. Now, the catch here is, if the CYA level is too high, then also it makes chlorine less effective. In a nutshell, the right balance of pool stabilizer or CYA is required to maintain a correct level of chlorine in the water.

reduce chlorine level in pool

If your pool is indoor and doesn’t get sunlight at all, only then you will not require CYA. CYA is available in many forms. For instance, in liquid or granule form, or mixed with chlorine tablets or sticks (trichlor) and in chlorine shock (dichlor). The CYA is generally added once at the beginning of the season but mostly the chlorine products you buy also contain CYA, so your pool gets a regular dose of stabilizer.

Chlorine level may vary as per the season, use more chlorine on a hot sunny day and less on a cloudy day. The pools that have more swimmers and heavier leaf debris require more chlorine to maintain pool hygiene. Moreover, pools that are equipped with highly efficient filtration and circulation systems, tertiary sanitizers like minerals, UV systems, may need 50% less chlorine for sanitizing.

Why Is The Chlorine Level In My Pool So High?

Very high levels of chlorine are a result of adding too much pool shock or putting a very high concentration of chlorine. Leaving a liquid chlorine pump overnight is the most common way of over-chlorinating the pool.

High levels of CYA slows down the natural degradation of chlorine. To curb over-chlorination, what you could do is reduce the amount of chlorine used after adding pool stabilizer.

lower chlorine levels in pool

What Amount Of Chlorine Is Considered Overly High?

over chlorinated pool

Sensitivity to chlorine may vary from person to person. Swimmers may experience itchy skin or irritable eyes and dry hair when free chlorine is above 5 ppm, Very high levels can irritate the esophagus and lungs when exposed for a longer period, specifically in indoor pools where the concentration of chlorine is naturally high due to the absence of sunlight.

You’ll be surprised to know that swimsuits fade out if the chlorine level is above 10 ppm and such high levels may not be considered healthy for swimmers. For overall swim comfort and safety, shut the pool and remove solar covers, until chlorine levels are below 5 ppm.

Testing Chlorine Levels

Very high levels of chlorine when get tested, 10 ppm is the maximum any tests by kits or strips, and if it is higher than 10 in that case DPD test samples bleach out or strips are clear. In such cases, you should dilute the test sample with half distilled water and make it double.

In such cases, you should dilute the test sample with half distilled water and make it double.

how to lower chloride levels in pool

For Example:

Throw out half of the water test vial and fill up with distilled water and then multiply test report ×2 to get readings above 10 ppm. The same thing can be achieved with test strips by adding a cup of pool water with a cup of distilled water or any sort of water that doesn’t have chlorine or a known, lower level of chlorine.

Various Pool Sanitization Methods:

how to lower chlorine levels

1. Add sodium thiosulfate, also called chlorine neutralizer for instant reduction

2. Ascorbic acid is added to water, also called Vitamin C to remove chlorine.

3. Hydrogen Peroxide is added, also known as H2O2, to break chlorine molecules.

4. Chlorine can be removed naturally with sunlight, aeration, and agitation of the water.

Sodium Thiosulfate

Most probably the cheapest and quite reliable solution to decrease chlorine levels, in pools or spas is sodium thiosulfate. About 8 oz of the dry white crystals per 5000 gallons of pool water or 1 oz per 100 gallons is required to lessen chlorine by 10 ppm. Firstly, one must check pool water pH, and add directly to the pool or spa.

how to reduce chlorine in swimming pool

Sodium Thiosulfate Dosage

lowering chlorine in pool

One has to be careful not to exceed the mark, or add too much of a dose to the pool with sodium thiosulfate, else one may face trouble adding new chlorine for some time.

One must follow the label instructions attentively while working with chlorine remover for dosages and water balance.

There is another very good resource, the sodium thiosulfate calculator on

Just type your pool size in gallons or liters and the current chlorine level in ppm, and it suggests you about what quantity of sodium thiosulfate to add to lower chlorine to zero.

Ascorbic Acid

Vitamin C in Granular form. Chlorine level can be lowered by adding 32 oz par 10,000 gallons of pool water by about 9 ppm. This is nothing but stain remover what we get in the market.

Hydrogen Peroxide

  • Use 1 gallon of aqua silk oxidizer per 10,000 gallons of pool water, to lessen chlorine level by 55 ppm.
  • To lessen chlorine level by approx 10 ppm for spas, 3% drug store Peroxide, 2 ounces per 100 gallons of spa water is required.

over chlorinated pool water

Checking Ph Levels Of Water To Determine What Amount Of Sanitizer Is Required

The ph level of the water also needs to be considered before adding chlorine in the pool water. The right level of chlorine won’t help if the pH level of the water is too high as chlorine is ineffective in acidic water. Such water is also not safe for swimming.

You must look for a ph balance that is the same as human tears i.e. 7.2 to 7.6. To reduce the high levels of pH, it is recommended to add muriatic acid in the deep end of the pool when the pump is running.

This will quickly mix the concentration and you can test the pH level again after six hours of adding this chemical. You can add chlorine, after making sure that the Ph balance is maintained and not fluctuating.

Try avoiding the chlorine tablets/stick that requires water running over them to dissolve as you will be required to put it in the skimmer basket, causing it to reduce pH level significantly and prematurely fail. Also, refrain from using tablets that fall apart. Use good quality tablets that will dissolve at an even rate, especially if those are floating chlorinators.

lower chlorine levels

You need to ensure that pH levels are checked every 2-3 days as the Ph level affects the efficiency of chlorine in sanitization. Also, bear in mind that chlorine needs to be neutralized first when it interacts with any contaminant and UV rays. You may try manipulating the size of the chlorine tablets, if a 1-inch tablet is not working then you may switch to a 3-inch tablet or try adjusting your chlorine feeder with an automatic system.

Pool owners prefer automatic chlorine feeders as they are easy to use and perfect for maintaining a good pool environment. These devices are an efficient means of automatically controlling the concentration of chlorine in the pool.

No matter, which system you choose to add chlorine to the water, make sure that chlorine level should remain between 1.0 and 3.0 ppm to maintain healthy pool chemistry.

Higher levels then this will involve risk of irritability of the skin and eyes. A certain amount of smell will be there given the concentration of chlorine in the pool but a strong smell is an indicator of organism deposits.

Also in such a case, you should go ahead and shock the pool to remove organic built up and other contaminants. How much chlorine is required to add in the pool, depends on the total gallons of water. After ascertaining the total volume of the pool water, consider adding one ounce of chlorine that will give you 1 ppm in 75000 gallons of water or 0.013 ounces of chlorine/100 gallons.

Minimizing High Chlorine and Bromine Levels in Spa Pools

Chlorine neutralizer will remove the chlorine and bromine from your hot tub, but leaving the jet pump open on high with the air blower running and leaving the hot tub uncovered can shrink a high concentration in just a few hours. However, if you are looking for hassle-free and quick results then, you can go for a very effective chlorine neutralizer or bromine neutralizer for turning down very high levels of chlorine or bromine.

Draining spa is another way of checking the levels of chlorine in water but that may damage your lawns and plants given the high concentration of chlorine. What you could do is either you can partially drain in the swimming pool or directly to a storm drain and refill again chlorine-free water to maintain an optimum level of sanitizer. Chlorine is less heavy than bromine, 1ppm of chlorine equals 2.5 ppm of bromine.

how to lower chlorine level in pool

Spa owners should use 3-5 ppm of bromine or if mineral sanitizer is being used then up to 1-3 ppm. Mostly, people can bear with up to 10 ppm of bromine or 5 ppm of chlorine for a short hot bath without any discomfort. A very high level of chlorine or bromine levels may leave an odor on the skin and hair of pool users. It is an alarming sign for the pool or spa managers to control the level of chlorine or bromine levels in the pool or spa.

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