POOL & WATER MAINTENANCE

How to Shock a Pool and How Long Does it Take?

Pools are lots of fun and bring families and friends together. However, pool maintenance can seem overwhelming, especially when it comes to balancing and shocking its water. Don’t worry, once you learn how to shock a pool, what chlorine to use, and other small tips, the process is quite easy. Continue reading for our step-by-step guide and additional information to help you shock your pool.

How to Shock a Pool


Pool shocking is the process of adding chlorine or non-chlorine pool chemicals to the water to raise the “free chlorine” level. This is done to destroy bacteria, algae, and more. It sounds intimidating, but the process is simple, and it will make swimming in your pool water safe for you and your family.

To shock your pool, you will need the following items:

  • Pool test kits
  • Pool shock – this comes in many forms
  • Water (depending on the type of shock you choose)
  1. Start by testing the water. This will tell you how much chlorine you need to add to the pool.
  2. Calculate the amount of shock chemical you will need to mix. It’s best to refer to the amount indicated on the package you are using.
  3. If your shock chemical needs water, add it now.
  4. Check to make sure your pool pump is running.
  5. Pour the mixture into the water around the edges of the pool.
  6. Let the pump run for about 8 hours or more, depending on what the shock chemical package suggests.
  7. Test the water to ensure proper chlorine levels.
  8. Wait for the chlorine levels to drop to around 1 to 3ppm before going into the pool.

How to Use Liquid Chlorine


Chlorine is the main chemical people use to keep their pools disinfected. Liquid chlorine is not stabilized and can evaporate if added to your pool during the daytime when the sun is shining, so liquid chlorine should be added after dusk. Learn more about the types of chlorine and when and how much chlorine to use to shock a pool.

How much chlorine do you need to shock a pool

To determine how much chlorine you need to shock a pool, you first need to know the amount of water in the pool. Generally, the dosage amount of pool shock is 1lb per 10,000 gallons, but you should always consult your shock package label.

Before you learn how to shock your pool, it’s important to understand the 3 main types of chlorine and how they affect your pool.

  • Free Chlorine – Free Available Chlorine is the amount of effective chlorine available to sanitize the pool water. It is effective and kills contaminants to disinfect the water. When people refer to pool shocking, they’re referring to the process of adding more chlorine to the pool to raise the Free Chlorine level. So this term is very important!
  • Combined Chlorine – the non-effective (dead) chloramines that form when there isn’t enough Free Chlorine present in the pool water.
  • Total Chlorine – also known as Total Active Chlorine, the total amount of Free and Combined Chlorine.

Types of pool shock

The type of shock you should use will depend on your water chemistry and the reason you are shocking. There are many different types of pool shock.
Here are the most common ones:

  • Sodium Hypochlorite: this is liquid chlorine that has about 10-12% active chlorine and is usually applied to a pool through an automatic chemical feeder. It’s used in big water parks and large commercial pools.
  • Lithium Hypochlorite: this has 35% active chlorine and dissolves very quickly. It’s expensive and used mostly for residential pool disinfecting.
  • Calcium Hypochlorite: this has about 40-78% active chlorine and is the most popular of the chlorines. It can be used to shock a pool and as an erosion feeder to disinfect pools. It’s used for residential and commercial pools.
  • Trichlor and Dichlor: both are stabilizing chlorines perfect for outdoor pools. The active chlorine levels are around 80-90% and are commonly used to treat pool problems due to algae.
  • Potassium monopersulfate (non-chlorine shock): this is a chlorine alternative oxygen-based shock. It can be used to oxidize, destroy contaminants, and help chlorine operate more efficiently. You can use it any time of day and swim 15 minutes later.

What Is Pool Shock?

Pool shock is the process of adding chlorine or pool chemicals to your water to raise the Free Chlorine level.

Why Shock Your Pool?

You shock a pool to raise the level of chlorine to a point where contaminants like algae and bacteria are destroyed. It keeps your pool water clear and safe to swim in.

How Long Does it Take to Shock a Pool?

The actual process of shocking your pool should not take longer than an hour, depending on the product used. However, it could be up to 8 hours before your pool is safe enough to swim in.

How Often to Shock Your Pool?

The more you use your pool, the more often you will need to shock it. We recommend shocking it weekly if you’re using it frequently.

How to Shock a Salt Water Pool?

Shocking a salt water pool is very similar to shocking a fresh water pool.
You’ll need:

  • a pool test kit
  • pool shocking chemicals
  1. Test your pool chemistry with a pool test kit.
  2. Balance your pool water to bring them into normal ranges, if needed.
    • pH: 7.4 – 7.6
    • Total alkalinity: 80 – 140 ppm
    • Calcium Hardness: 200-400
  3. Turn on your pool filter and add the shock to your pool using the shock chemical instructions.
  4. Turn down the salt cell system.
  5. After all this, your pool water should be a cloudy blue. Keep running your filter until the water is clear.

How to Shock a Green Pool?


Don’t worry, if your pool is green, it can be fixed with pool shocking! Usually, a green pool means there is little to no chlorine in the pool.

You’ll need the following items:

  • test kit
  • filter cartridges (optional, in case you need to replace yours)
  • brushing to clean the jets
  • pool shock chemicals.
  1. Start by testing the pH with a testing kit.
  2. Balance the pH to normal levels.
  3. Turn on your pool filter.
  4. Use calcium hypochlorite in the pool.
  5. Run the filter for 24 hours to let the algae and other bacteria in the pool start to clear out through the filter.
  6. After 24 hours, you will see your pool go from green to cloudy.
  7. Brush and filter for the next few days to remove all the green and cloudiness. You’ll want to clean your filters multiple times to remove build-up.

After you’re done getting your pool back to normal, don’t let it go green again! Perform weekly pool maintenance to keep your pool in perfect condition.

How Long After You Shock a Pool is it Safe to Swim?


The wait time depends on the type of pool shock you’ve used. Always refer to the package to determine how long you need to wait, but most pool shock requires you to wait 8 hours before it’s safe to swim.

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