What Is Free Chlorine VS Total Chlorine in a Pool – Test the Difference (2021)

Free Chlorine

If you own or frequent a swimming pool or are just well-versed in clean drinking water, you will have heard of chlorine as an additive to water to keep you safe from impurities, whether swimming or drinking.

Chlorine is chlorine, right? Why on earth would you call chlorine “free”?

The answer to the first is “No”, not all chlorines are equal and as to “free” chlorine, we’re going to try to explain it in this article.

What is chlorine?

Chlorine is a chemical element that is often added to drinking water globally to guarantee that your drinking water is clean and free from germs.

This particular element is highly effective in killing bacteria through a chemical reaction.

Adding the correct amount of chlorine whether to a swimming pool or at a treatment plant for water can keep the water germ-and-impurity-free.

You can add chlorine directly to a swimming pool where it separates into various smaller chemicals like hypochlorous acid and hypochlorite ion which are extremely effective in killing bacteria or microorganisms in pools, thus making it an ideal disinfectant.

It is used in numerous and various types of products.

Thanks to its disinfecting and bleaching qualities, you will often find it in household cleaning products, as well as in textiles, paints, and even paper.

Chlorine combined with ammonia will oxidize bacteria rendering them harmless.

It is even utilized in the manufacturing of the plastic material PVC used in the manufacturing of tubing, flooring, and window frames.

Chlorine in the Swimming Pool

The use of chlorine in a swimming pool is very effective in keeping the water sanitized, however, it is fundamental to use a chlorine test to maintain the correct chlorine levels, by using the correct amount.

Chlorine is a strong type of chemical, so in keeping your pool clean, the correct amount is everything.

The high chlorine content in water can contribute to irritated and itchy skin.

Benefits of Using Chlorine

The primary benefit is that it is highly effective in eliminating contaminants. It is also:

  • reasonably inexpensive
  • less harmful than other solutions
  • effective in offering long-term protection against contamination

The only negatives associated with its use are its strong odor and less effectiveness when used in dark cloudy pools.

Chlorine Types – Free Chlorine vs Total Chlorine

Chlorine can be characterized into three types:

  • Free chlorine refers to the quantity of chlorine that has not been added to water to sanitize. It is free to eliminate germs and microorganisms
  • Combined chlorine develops while it is in the process of sanitizing your swimming pool
  • Total chlorine is the combined total of the first two and its measurement, by using a chlorine tester, can be important for numerous reasons

Free chlorine refers to the specific amount of chlorine that can sanitize any type of contaminant.

Combined chlorine refers to chlorine that has been combined with contaminants and total chlorine is the sum of the first two types.

In other words, free chlorine + combined chlorine = total chlorine.

Measuring Free Chlorine and Combine Chlorine

If you need to sanitize your swimming pool, it’s important to monitor free chlorine levels.

If there is an insufficient amount, it won’t be effective in keeping your pool clean and eliminating germs and bacteria.

When checking the free chlorine in your swimming pool, the measurement should read between 2 parts per million and 4 parts per million.

As this chlorine has not yet been used, it is really important because it is present and ready for disinfecting.

When you measure the combined chlorine in your pool water, it should read less than 0.5 PPM otherwise you will need to “shock” your pool to rid it of the strong chlorine odor associated with higher measurements.

When combined chlorine shows in measurements, it signifies that free chlorine is doing its job in breaking down contaminants.

When your pool is completely disinfected the water should measure zero combined chlorine.

Therefore, if you always maintain the correct amount of free chlorine, your pool water will rarely show any combined chlorine.

When testing for total chlorine, you may be testing for free chlorine combined with the correct level of combined chlorine, which should read zero.

If it’s not, the test is useless because it doesn’t indicate separate chlorine amounts, just the chlorine total.

The ideal solution is to have sensors for measuring free chlorine, combined chlorine, and total chlorine.

While it would be ideal to test the free and combined chlorine in your water daily, every other day is sufficient.

This is important if you own an outdoor uncovered pool.

Free Chlorine Test

Free Chlorine Test

There are three types of testing used for chlorine measurements

  • test strips which consist of a chemical pad inserted in the water
  • test kits which have you add reagent drops to a sample of the water
  • electronic or digital sensors for testing which is the most accurate giving precise readings of components

Free Chlorine FAQs

What is free chlorine?

Free chlorine denotes hypochlorous acid and hypochlorite ions added to pool water for disinfection.

How do you increase free chlorine?

Add a sufficient amount to your pool which achieves a breakpoint chlorination level in your pool water.

Why is there no free chlorine in my pool?

Your pool may need greater quantities of total chlorine, and the actual level may be ineffective for disinfecting.

How do I test for chlorine in the water?

You can test the water by utilizing chlorine test strips, a chlorine testing kit, or by installing a digital sensor probe.

How do I lower the level of chlorine in my pool?

The level can be lowered by several methods:

  • Avoid adding chlorine and it will gradually lower the level
  • Sunlight exposure will lower the level
  • Adding sodium thiosulfate will lower the level
  • Adding hydrogen peroxide will reduce the level
  • Replace some of your pool water

How do I raise the chlorine level in my pool?

Add chlorine to your pool to bring the level up to the breakpoint chlorination level. Monitor the free, combined chlorine, and total chlorine level.

What is the ph of chlorine?

If the ph level is 5, it will be hypochlorous acid.

If it reads 8.5, it will be hypochlorite ion.

The ideal reading for pools should be 7.4 which is also the ph level for eyes and mucous membranes and yet is still effective as a disinfectant.

What happens if chlorine levels are too high?

Pool water which is overchlorinated can irritate the skin causing itching and general discomfort.

An exceptionally high reading can cause poisoning with symptoms including nausea, vomiting, burning sensations, itchy eyes, irritated red skin, and breathing difficulty.

What does “shocking” a pool do?

Shocking refers to adding chemicals to raise the free chlorine level in the pool, thus destroying bacteria, algae, and contaminants in general.

How do I measure chlorine granules?

By using a measuring device or even the cap and then adding to the pool water.

Free Chlorine – The Bottom Line

Chlorine-based products are necessary to keep your pool water safe from contaminants and infections while protecting friends and family during the enjoyment of warm days.

Free chlorine is necessary but should be frequently measured along with combined chlorine and total chlorine, and handled with care.