Maintaining a clean, safe, and healthy swimming pool requires regular maintenance and using the right pool chemicals. Two essential components of pool care are sanitizers and shock treatments. While both are crucial in keeping your pool water clean and contaminant-free, they serve different purposes and are used differently.

This article will explore the differences between pool sanitizers and shock treatments and help you understand when to use each for the best results.

Pool Sanitizer Vs Shock

What is a Pool Sanitizer?

A pool sanitizer is a chemical continuously added to your pool water to kill bacteria, viruses, and other harmful microorganisms. The most common pool sanitizers are:

  1. Chlorine: Available in liquid, granular, or tablet form, chlorine is the most widely used. It effectively kills a wide range of contaminants and is relatively inexpensive.
  2. Bromine: An alternative to chlorine, bromine is gentler on the skin and eyes and has a lower pH impact. It’s often used in hot tubs and indoor pools.
  3. Salt: Saltwater pools use a salt chlorinator to convert salt into chlorine, providing a consistent and automated sanitizing process.
  4. Mineral Systems: These systems use minerals like silver and copper to sanitize the water, often in combination with a low chlorine or bromine level.

Pool sanitizers maintain a constant level of disinfectant in the water, preventing the growth and spread of harmful organisms. The ideal sanitizer level varies depending on the type of sanitizer used. Still, generally, you should aim for:

  • Chlorine: 1-3 ppm
  • Bromine: 3-5 ppm
  • Salt: 0.5-1 ppm (salt level), which generates 1-3 ppm of chlorine

What is Pool Shock?

Pool shock, also known as superchlorination, is when a high dose of chlorine or non-chlorine shock is added to the pool water to quickly eliminate contaminants, destroy chloramines (combined chlorine), and restore water clarity. The two main types of pool shock are:

  1. Chlorine-based shock: This type of shock contains a high concentration of chlorine, usually in the form of calcium hypochlorite or lithium hypochlorite. Chlorine-based shock is fast-acting and effective against a wide range of contaminants.
  2. Non-chlorine shock: Also known as oxidizing shock, this type of shock uses oxygen-based compounds like potassium monopersulfate to oxidize contaminants without adding chlorine to the water. Non-chlorine shock is ideal for people sensitive to chlorine or wanting to avoid a strong chlorine odor.

Pool shock is typically applied once a week or as needed when the water appears cloudy, has a strong chlorine smell, or after heavy pool usage or rainfall.

What is Pool Shock

Key Differences Between Pool Sanitizers and Shock

Now that we’ve defined pool sanitizers and shock treatments, let’s look at the key differences between them:

  1. Purpose: Pool sanitizers are used to maintain a consistent level of disinfectant in the water, while shock treatments are used to eliminate contaminants and restore water clarity quickly.
  2. Frequency of use: Sanitizers are continuously added to the pool water, either manually or through an automated system. Shock treatments are performed once a week or as needed.
  3. Concentration: Pool sanitizers are added in lower concentrations to maintain a steady disinfectant level, while shock treatments involve adding a high dose of chlorine or non-chlorine shock to the water.
  4. Effect on water chemistry: Pool sanitizers can affect the pH and alkalinity of the water over time, requiring regular testing and adjustment. Shock treatments can temporarily raise the chlorine level and may affect the pH, depending on the type of shock used.

When to Use Pool Sanitizer

Pool sanitizer should be used continuously to maintain a constant level of disinfectant in the water. This helps prevent the growth of bacteria, viruses, and algae, keeping your pool water clean and safe for swimming. Here are some guidelines for using pool sanitizer:

  1. Test the water regularly: Use a reliable test kit to measure the sanitizer level, pH, and alkalinity of your pool water at least once a week, or more often during heavy use.
  2. Maintain the proper sanitizer level: Add sanitizer as needed to keep the level within the recommended range for your specific type of sanitizer.
  3. Monitor and adjust pH and alkalinity: Regularly test and adjust the pH and alkalinity levels to ensure your sanitizer’s effectiveness and prevent swimmer discomfort or equipment damage.
  4. Use a consistent sanitizing method: Choose a sanitizing method that works for your pool and stick with it to maintain stable water chemistry and avoid complications.

When to Use Pool Shock

Pool shock should be used in the following situations:

  1. Weekly maintenance: Shock your pool once weekly to eliminate contaminants, destroy chloramines, and maintain water clarity.
  2. After heavy pool usage: If your pool has been used by many swimmers or for an extended period, shock the water to remove excess contaminants and restore sanitizer levels.
  3. After a rainstorm: Rain can introduce contaminants and dilute your pool water, making it necessary to shock the pool to restore proper water chemistry.
  4. When water appears cloudy or has a strong odor: If your pool water looks cloudy or has a strong chlorine smell (indicating the presence of chloramines), shock the pool to clarify the water and eliminate odors.
  5. When opening or closing your pool: Shock your pool when opening it for the season to remove any contaminants that may have accumulated during the off-season, and shock again when closing the pool to ensure clean water for the next season.

Pool Sanitizer vs Shock: FAQs

Can I use pool shock and sanitizer simultaneously?

It’s generally recommended to shock your pool at night or when it is not in use, as the high chlorine levels can irritate swimmers. After shocking, allow the chlorine level to return to the normal range (1-3 ppm) before using the pool again. You can continue to use your regular sanitizer after shocking, following the recommended dosage and testing the water to ensure proper levels.

How long after shocking can I add sanitizer to the pool?

You can add sanitizer to your pool immediately after shocking, as the shock treatment will not interfere with the sanitizer’s effectiveness. However, test the water and adjust the sanitizer level as needed to maintain the proper range.

Do I need to use chlorine and non-chlorine shocks?

Depending on your preferences and pool needs, you can choose to use either chlorine-based or non-chlorine shock. Some pool owners alternate between the two types of shock to take advantage of the benefits of each. Chlorine shock kills many contaminants, while non-chlorine shock oxidizes contaminants without adding chlorine to the water.

Will pool shock affect my pool’s pH level?

Some types of pool shock, particularly chlorine-based shock, can temporarily raise the pH level of your pool water. It’s essential to test the pH after shocking and adjust it to maintain the ideal range of 7.2-7.6. Non-chlorine shock generally has minimal impact on pH levels.

Can I over-shock my pool?

It is possible to over-shock your pool by adding too much chlorine or non-chlorine shock. This can lead to high chlorine levels that irritate swimmers and damage pool surfaces and equipment. Always follow the manufacturer’s instructions and use the appropriate dosage based on your pool’s size and water volume. If you accidentally over-shock your pool, allow the chlorine level to naturally dissipate or use a chlorine neutralizer to bring the levels back to normal.


Understanding the difference between pool sanitizers and shock treatments is crucial for maintaining a clean, safe, and enjoyable swimming environment. Pool sanitizers work continuously to prevent the growth of harmful organisms, while shock treatments are used periodically to eliminate contaminants, destroy chloramines, and restore water clarity.

Using pool sanitizers and shock treatments appropriately and with regular water testing and maintenance, you can keep your pool water sparkling clean and inviting all season long. Always follow the manufacturer’s instructions, use the right dosage, and allow proper time for the chemicals to work effectively.

Remember, a well-maintained pool is a safe and healthy, so stay on top of your pool care routine and enjoy the benefits of your backyard oasis!