Types of Chlorine You Can Use In Your Pool

Swimming pools can be full of bacteria if they are left unsanitized. And this is why chlorine is an essential part of swimming pool maintenance. It is one of the most common swimming pool sanitizers because it is economical and effective.

But did you know chlorine comes in several different types? While the type of chlorine you use ultimately depends on the make of your pool, understanding the differences between them and how they are used can be helpful knowledge for pool owners.

In this article, I will discuss the five types of chlorine and their pros and cons, so let’s dive in!


Main Takeaways

  • There are five types of chlorine: sodium hypochlorite, calcium hypochlorite, lithium hypochlorite, trichlor, and dichlor.
  • Each type offers various advantages and disadvantages; for example, lithium hypochlorite is expensive but fast-dissolving.
  • The pool chlorine you choose will depend on factors such as whether or not you are shocking your pool and your pool water chemistry.

What Are The Different Types of Chlorine?

There are five types of chlorine: sodium hypochlorite, calcium hypochlorite, lithium hypochlorite, trichlor, and dichlor. Each type has a different purpose depending on your pool. These five types of chlorine can be divided into two main categories: stabilized and unstabilized.

Sodium hypochlorite, calcium hypochlorite, and lithium hypochlorite are unstabilized. In other words, these types of chlorine do not have cyanuric acid, which acts like a sunscreen for your chlorine, preventing it from breaking down from the sun’s UV rays. On the other hand, trichlor and dichlor are stabilized chlorine, so they contain cyanuric acid.

Pros and Cons of The Different Types of Chlorine

Each type of chlorine has both advantages and disadvantages. I will cover each type in detail and explain their pros and cons below.

Sodium Hypochlorite

Sodium hypochlorite is a liquid chlorine or bleach. It is the most commonly available type of chlorine used by pool professionals. It is a popular choice as it is very economical and has been widely used since the 18th century. This chlorine also has a naturally high pH level of 13 and a chlorine concentration of around 10% by volume. It’s best used for large public pools. Sodium hypochlorite is arguably the safest, easiest, and cheapest chlorine type to handle.

Pros:

  • It is very cost-effective and easily available.
  • It is very effective in eradicating microorganisms and is good at removing stains.
  • It is an excellent solution for pools with high calcium hardness.

Cons:

  • It has a limited shelf life and can easily lose potency if stored poorly.
  • As a liquid chlorine, it is a lot heavier than tablets or granules.
  • With a pH level of 13, you may need to rebalance your water with muriatic acid.

Calcium Hypochlorite

Calcium hypochlorite is a granular chlorine used for shock. It is mainly used for small private pools and is easy and safe to use. This type of chlorine is commercially available in a powder form or as tablets and is sold with 65% to 75% chlorine concentration. It has a naturally high pH of about 12.

Pros:

  • A cost-effective chlorine type.
  • Since it is available in powder or tablet form, it is very safe to use and dissolves quickly.
  • It has an excellent shelf life and can be stored for a long time without losing potency.

Cons:

  • It can raise the calcium hardness levels of your pool water if left unchecked; this can cause scaling on plaster or a buildup on your pool equipment.
  • For consistency, the tablet form of calcium hypochlorite requires special equipment to add it to the water, which is an additional expense.
  • Since it is a strong oxidizer, it is a very volatile substance and can combust if left near other substances (including other types of chlorine), making it a potential fire hazard.

Lithium Hypochlorite

Lithium hypochlorite is a dry granular form of chlorine. The volume of chlorine available in this form is around 28% to 35%, making it weaker than calcium hypochlorite. Lithium hypochlorite is slightly more expensive than other chlorine options – primarily due to the high demand for lithium in other industries, such as batteries.

Pros:

  • It has a very fine consistency and dissolves rapidly, making it most suitable for fiberglass or vinyl pools.
  • It has a longer shelf life than the other two unstabilized chlorine types.
  • It is not a fire hazard.

Cons:

  • More expensive compared to other chlorine types.
  • It contains less chlorine than calcium hypochlorite.

Trichlor

Trichlor is a powerful, dry solid substance with around 90% available chlorine – the highest level of chlorine available you can get. Trichlor is a stabilized chlorine since it is a mixture of chlorine and cyanuric acid. It is commercially available in tablet form and can be dispersed by a floating container. It is also acidic and has a pH level of about 3.

Pros:

  • Trichlor is one of the most cost-effective options since it has a long and stable shelf-life, has a high chlorine level, and dissolves quite slowly.
  • It is safe and easy to use for private pool owners.
  • Since it is acidic, trichlor can stop the pH from rising naturally.

Cons:

  • The acidity level can also be a disadvantage, as trichlor tabs can corrode pool equipment and etch pool surfaces.
  • Since it has a low pH level of about 3, it is acidic and can lower your pH – you might need a pH increaser to keep your pool at the desired level of 7.2-7.8.
  • Trichlor can raise your cyanuric acid levels (CYA) by 0.6 ppm for each 1.0 ppm of chlorine added, which can only be adjusted by the water being drained and refilled. High CYA can slow down the chlorine’s killing speed.

Dichlor

Dichlor is more commonly available in a granular form, although it also is sold as tablets. This type of chlorine is also used as a shock treatment. The free chlorine available in dichlor is around 55% to 65%, making it less potent than trichlor. It has a neutral pH of approximately 6.2-7 and contains cyanuric acid, which makes it a stabilized substance. However, it does contain a lot of CYA, which makes it trickier to use since too much CYA can make it difficult for chlorine to work effectively.

Pros:

  • Dichlor dissolves very quickly and easily, whether in granular or tablet form. If used in tablet form, it can be added to the pool skimmer or an automatic chlorinator for ease of use.
  • It has a fairly neutral pH level, which means you do not have to fiddle with the water chemistry of the pool to adjust alkalinity or acidity.
  • It has a stable shelf-life and stores well, as long as it is sealed in an airtight container.

Cons:

  • Dichlor is more expensive than trichlor, making it less cost-effective in comparison.
  • It is a fairly volatile substance and can explode if mixed with other chemicals, even in minimal amounts or if stored improperly. 
  • In the granular form, due to its fast-dissolving nature, it cannot be introduced using an automated feeding system and must be added manually, which means more work for a pool owner.

What Type Of Chlorine Is Best For You?

The best type of chlorine for you ultimately comes down to your preferences, needs, pool type, and water’s natural chemistry.

For instance, if you have a pool with low cyanuric acid levels and a low budget, you could use trichlor, which is a fast-dissolving substance that will raise the levels of CYA in your water. It also contains a high chlorine concentration, so you get more bang for your buck.

If you have a higher budget, you could opt for lithium hypochlorite, which is also fast-dissolving, while using a pool stabilizer to manually adjust the cyanuric acid levels.

If you are an expert at balancing water chemistry and have a tight budget, you could opt for sodium hypochlorite, an inexpensive option that may, however, affect your pH levels, which you’ll need to adjust accordingly.

If you’re looking to shock your pool, you should use calcium hypochlorite or dichlor. Cal-hypo is the cheaper option of the two, but it may require you to adjust the calcium hardness levels. I go over more tips on the right type of chlorine for shocking in my guide on pool shock vs. other chlorine. You can also view all the steps in my how to shock a pool article.

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If you have doubts about which chlorine to opt for, you could always contact a pool professional or reach out to me with your questions! I would be happy to help address any doubts. And make sure to check out my pool maintenance routine article for more tips on keeping your pool clean.

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