Dichlor vs. Trichlor: What’s The Difference?

Written by Michael Dean
August 25, 2023

dichlor vs. trichlor

Many pool owners use stabilized chlorine, specifically dichlor or trichlor, as they contain cyanuric acid, which helps protect the chlorine from the sun’s UV rays. But how do these two types of stabilized chlorine differ, and how do you decide which one to use?

In this article, I will compare dichlor and trichlor so that you can decide which chlorine type is best for you.

Main Takeaways

  • Dichlor is easy to use and does not cause changes in pH. However, it requires careful monitoring and is more expensive.
  • Trichlor is slow-dissolving, easy to use, and has a long shelf life. But it has high pH and is not suitable for shocking.
  • The main differences between dichlor and trichlor lie in chlorine concentration, dissolution rate, type, pH level, suitable pool types, and price.
  • Use trichlor for continuous chlorination and dichlor for routine maintenance and shock treatments.

What Is Dichlor?

Dichlor is a type of chlorine also known as Dichloro-S- Triazinetrione. It is a chemical compound that contains both chlorine and cyanuric acid. Dichlor is typically sold in granular or tablet form, making it easy to measure and add to the pool water. Dichlor has a chlorine concentration of around 55% to 62% and has a relatively neutral pH of 6.5.

Pros And Cons Of Dichlor

Like any pool sanitizer, dichlor has both advantages and disadvantages. Here are some of the pros and cons of using dichlor for your swimming pool.


  • High concentration of chlorine: Dichlor has a high concentration of available chlorine, making it very effective for sanitizing your pool.
  • Easy to use: Dichlor is available in granular or tablet form, making it easy to measure and add to the pool water. It also has a longer shelf life than other chlorine sanitizers.
  • Stable: Dichlor is a stabilized chlorine, meaning it contains cyanuric acid. So, if you have low CYA levels and low chlorine, this is a great way to kill two birds with one stone.
  • No big changes to pH: As dichlor has a neutral pH, it won’t significantly impact your pool’s pH level.


What is Trichlor?

Trichlor, also known as Trichloro-S-Triazinetrione, is a type of stabilized chlorine. It is a slow-dissolving tablet with a strong odor. Trichlor contains up to 90% available chlorine. It has a low pH level, typically around 3, which means that it is highly acidic.

Pros And Cons Of Trichlor

Here are the pros and cons of using trichlor in your pool.


  • High chlorine concentration: Trichlor has a very high concentration of chlorine, which makes it effective in killing bacteria, viruses, and other harmful microorganisms that can contaminate pool water.
  • Slow-dissolving: Trichlor releases chlorine over a longer period. This makes it ideal for use in automatic chlorinators, as it can provide a steady and consistent level of chlorine to the pool.
  • Long shelf life: Trichlor has a long shelf life, so you can buy it in bulk.
  • Affordable: Trichlor is more affordable than many other chlorine types, including dichlor.
  • Stable: Trichlor contains cyanuric acid, which protects the chlorine from breaking down in the sun.


  • Low pH: Trichlor has a low pH level, which can cause the pool’s pH levels to drop significantly.
  • High cyanuric acid levels: As mentioned, trichlor contains cyanuric acid, but too much of it can reduce the effectiveness of chlorine.
  • Not suitable for all pool types: Trichlor is not recommended for use in vinyl-lined pools, as it can cause the liner to deteriorate.
  • Not suitable for shocking: You can’t use trichlor to shock your pool.

Main Differences Between Dichlor And Trichlor

Dichlor and trichlor are two common chlorine sanitizers used in outdoor pools. While both types of chlorine can effectively sanitize pool water, several key differences exist between them.

Chlorine Concentration

Trichlor has a higher concentration of available chlorine than dichlor. While dichlor contains around 56% available chlorine, trichlor contains about 90% available chlorine.

Dissolution Rate

Dichlor dissolves quickly in water, while trichlor dissolves more slowly. This means that trichlor provides a slower, more consistent release of chlorine over time, while trichlor’s release is more immediate.

pH Level

Dichlor has a higher pH level than trichlor. While dichlor has a pH level of around 6.5, trichlor has a pH level of around 3. This means using dichlor is less likely to cause a significant drop in the pool’s pH level than using trichlor.


Dichlor can be found in either tablet or granular form, while trichlor can only be found as tablets. 

Suitable Pool Types

Dichlor is suitable for all types of pools, including vinyl pools. However, trichlor is not recommended for use in vinyl pools, as it can cause the liner to deteriorate over time due to its low pH.


Neither dichlor nor trichlor is the most expensive form of chlorine available, but dichlor is much more expensive than trichlor. In fact, dichlor granules may cost nearly twice as much as trichlor tablets. For example, if we look at In The Swim’s products, 10 pounds of dichlor will cost around $147, while 10 pounds of trichlor will cost approximately $90.

In The Swim Chlorine Shock Granules (Dichlor)
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In The Swim 3-Inch Stabilized Chlorine Tablets (Trichlor)
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I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Summary of the Main Differences Between Dichlor And Trichlor

Chlorine ConcentrationAround 56%Around 90%
Dissolution RateDissolves more quicklyDissolves more slowly
pH Level6.53
TypeGranular or tabletTablet only
Suitable Pool TypesAll pool typesNot recommended for vinyl pools
Price10 pounds for around $14710 pounds for around $90

When To Use Dichlor In Your Pool

Understanding when to use dichlor in your pool can help you effectively maintain your pool. Here are the scenarios in which I commonly recommend dichlor.

Regular Maintenance

Dichlor is ideal for routine pool maintenance. Its high concentration of available chlorine ensures efficient and effective sanitization, keeping the pool water clean and free from harmful microorganisms.

Shock Treatments

Dichlor is often used as a shock treatment to rapidly increase chlorine levels in pools experiencing contamination or algae growth. Its high chlorine concentration provides a powerful sanitizing effect, effectively eliminating organic contaminants and restoring water clarity.

Low Cyanuric Acid Levels

Check your CYA levels; if they are lower than the recommended 30-50 ppm, adding dichlor can be a good way to raise both your CYA and chlorine levels. 

When To Use Trichlor In Your Pool

Trichlor is a popular chlorine sanitizer that can be suitable for certain pool maintenance scenarios.

Continuous Chlorination

Trichlor is ideal for maintaining a consistent chlorine residual in your pool. Its slow-dissolving nature allows for a gradual release of chlorine, ensuring continuous sanitization over an extended period. Trichlor is often used in pool floaters or automatic chlorinators to maintain a stable chlorine level in the pool. This is the perfect choice for pool owners looking for a low-maintenance solution for sanitizing the pool.

Low Cyanuric Acid Levels

Just like dichlor, trichlor contains CYA, a stabilizer that protects chlorine from degradation due to sunlight exposure. If you have low cyanuric acid levels, use trichlor to add CYA along with the needed chlorine.

High pH

Trichlor is acidic with a pH level of 3, so if you’re battling high pH levels, trichlor can potentially help lower your pH. But this is not a true fix! The only real methods to lower pH are to use sodium bisulfate or muriatic acid. On the other hand, if you already have low pH, do not use trichlor.

Should You Use Trichlor or Dichlor To Shock Your Pool?

To shock your pool, if you must choose between trichlor and dichlor, use dichlor. Dichlor may not be as powerful as a shock as the more popular calcium hypochlorite, but it is still effective. However, cal-hypo is the best type of chlorine to shock your pool. One advantage dichlor has over cal-hypo is that it can be added during the day since it’s stabilized. But you’ll still need to wait at least 8 hours before you jump back into the pool. And make sure you test the water to ensure the chlorine levels are between 1 to 3 ppm before swimming.

Get My Free Pool Care Checklist

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Frequently Asked Questions

Can you mix trichlor and dichlor?

Do not mix trichlor and dichlor. In fact, do not mix any types of chlorine. Mixing can lead to uncontrolled reactions and the release of harmful gases, causing a potential hazard to your health and pool equipment. Use each product separately and follow the manufacturer’s instructions for proper application and storage.

Does dichlor have stabilizer in it?

Yes, dichlor contains cyanuric acid, a stabilizer that protects chlorine from sunlight degradation.

What is the best chlorine for a pool?

The best type of chlorine for a pool depends on your specific needs and your pool. Trichlor may be a good option if you have a slightly high pH level and are looking for a low-maintenance option. On the other hand, dichlor is ideal for routine maintenance and shock treatments. There are also other types of chlorine to consider, such as cal-hypo, sodium hypochlorite, and lithium hypochlorite.

Bottom Line

Dichlor and trichlor are both types of stabilized chlorine that can be used to sanitize swimming pools. They can be used similarly; however, they have different uses and should never be mixed. 

Have any more questions about how the different types of chlorine? Check out my article comparing all of the different types of chlorine.

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