How to Shock a Swimming Pool

Written by Michael Dean
July 7, 2023

shocking a swimming pool

Shocking is an inevitable part of pool maintenance. Shocking your swimming pool will eliminate the accumulation of chloramines and the strong smell of chlorine. It will also help kill bacteria and algae that have built up over time and clear cloudy water. Not quite sure where to start? In this article, I’ll guide you through how to shock a swimming pool.

Let’s get right into it with the steps you need to take to successfully shock your pool. If you’re a little more unfamiliar with the shocking process, skip down and read about how shocking works, types of shock, when to shock, and other tips.

Main Takeaways

  • To shock a swimming pool, you should test the water, calculate how much shock to use, ensure the pump is working, pour the shock into the pool, and test the water again.
  • To successfully shock your pool, you need to reach breakpoint chlorination, which is a ratio in which free chlorine is 10 times higher than chloramines.
  • You can shock a saltwater pool, but stick with dichlor or non-chlorine shock only.
  • Ensure you follow all safety protocols when handling chlorine, including wearing proper PPE gear, testing the water, and checking the labels.

Step-by-Step: How to Shock a Swimming Pool

If you want to shock your pool successfully, you should raise the free chlorine level to about ten times higher than the number of chloramines. This ratio will effectively break up those harmful bonds and make your pool clean again. Let’s start with some necessary supplies and then get into the steps for shocking your pool.

Supplies Checklist

  • Water testing kit or test strips
  • Enough pool shock to fix your chlorine ratio
  • A mixing bucket
  • Personal protective gear (Glasses, gloves, and full-cover clothing)
  • Brush or pool vacuum for final touch-ups

Step 1: Test the Pool Water

The first step in shocking the pool is to test the water and calculate the current chlorine levels. If your combined chlorine level is higher than your free chlorine level, you’ll know it is time to shock your pool. To find your combined chlorine (CC) level, you deduct the free chlorine (FC) from the total chlorine (TC).

While you are testing the chlorine levels, you should also go ahead and test your pH, alkalinity, and calcium hardness, as these all play a role in the effectiveness of your chlorine. Your pH should sit between 7.2 and 7.8. Your alkalinity should be 80 to 120 parts per million (ppm), and your calcium hardness should be 175 to 275 ppm. Check out my article covering pool chemistry for more on this.

Step 2: Calculate the Amount of Shock to Use

The next step is to calculate the optimal amount of shock to prepare. Check the instructions on the packaging, use my pool calculator to determine the volume of your pool (i.e., how many gallons of pool water you have), and use my pool shock calculator to determine the amount of shock you need to add. Most types require you to mix shock in a bucket to dissolve.

Step 3: Make Sure the Pump is Working

Next, you should ensure that the pool pump and filter are operating at full power so the pool shock can mix and thoroughly circulate throughout the pool.

Step 4: Dump Shock in the Pool

After confirming that the pool pump works well, you can dump the pool shock solution into the outer edge of the water. Once you dump the pool shock into the water, allow the pump to keep running for at least eight hours. Grab a drink and relax a bit!

Step 5: Test the Water Again to Check for Optimal Chlorine Levels

After those eight or more hours, you should test the water again to check for proper chlorine levels and other pool chemicals. You should aim for ten times more free chlorine than the combined chlorine levels.

If you’re still having trouble getting your pool’s free chlorine levels to the right spot, you may need to SLAM your pool.

Here’s a good video on the entire pool shocking process outlined above.

What is Pool Shock?

Pool shock is simply a large dose of chlorine administered at once, though it can be another type of sanitizer. Pool owners use shock in their pools to replenish “used-up” combined chlorine with free chlorine. This is done by super-chlorinating your pool water with a heavy dose of sanitizer. Doing this not only helps sanitize your pool and kill bacteria and algae in the water but also oxidizes the potentially hazardous chloramines in the water, which are a byproduct of chlorine that occurs when chlorine molecules come into contact with sweat, oils, or other contaminants.

The typical chlorine scent you associate with pools is actually the chloramines in the water, so if you smell a strong chlorine smell, it is likely an unclean pool that needs to be shocked.

Different Types of Chlorine

You should get to know a few different types of chlorine before you start chucking pool shock into your pool. As mentioned above, to properly determine how much chlorine to add to your pool, you need to know how to test for the free and total chlorine levels. This will help you determine the amount of combined chlorine in your pool. Here is a quick breakdown of the different types of chlorine.

Free Chlorine

Free chlorine is the golden boy of the chlorine family. This is essentially your pool’s reserve of chlorine molecules that are ready to fight off and oxidize contaminants in your pool. Think of chlorine as the new soldiers just deployed for battle.

Combined Chlorine

Combined chlorine is what you don’t want a lot of. This occurs when your free chlorine molecules oxidize the contaminants in your pool. The chlorine molecule then binds with the ammonia in the contaminant. When this happens, the chlorine is no longer active, so it cannot fight off any more unwanted contaminants. Combined chlorine, also known as chloramines, is what you generally get rid of when you shock your pool. Think of combined chlorine as the worn-out soldiers that have been fighting the war for some time now and are ready to be changed with new ready-for-battle soldiers.

Total Chlorine

Total chlorine is just the total amount of chlorine in your pool, including the total and combined chlorine. To find the combined chlorine level, you subtract the free chlorine from the total chlorine.

Breakpoint Chlorination

Breakpoint chlorination is a term that refers to the process in which a pool is super-chlorinated to the point that the free chlorine WAY outnumbers the chloramines, generally a 10:1 ratio. Essentially, it is necessary to reach breakpoint chlorination to successfully shock your pool. Reaching breakpoint chlorination will allow you to oxidize all of your chloramines, replacing them with free chlorine ready for duty!

Types of Pool Shock

So, what are the different kinds of pool shock? There are many different products that you can utilize, but here are the most popular and effective ones. For recommendations on specific pool shock products, read my guide on the best pool shock.

Calcium Hypochlorite

Also known as cal hypo, this chemical is a more affordable and practical option for shocking your pool. You can usually find calcium hypochlorite at the pool or hardware store in a granular condition. This type of shock must be dissolved in water before adding it to the pool. I recommend using this product at dusk, as UV rays can interfere with the process. And as a plus, you can sleep off the 8-hour wait before safely entering the pool again. One last note on cal hypo – this shock won’t affect your pool’s cyanuric acid level.

In The Swim Calcium Hypochlorite Chlorine Granular Pool Shock

In The Swim has a reliable cal hypo shock that is effective and easy to use.

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Lithium Hypochlorite

While cal hypo will add extra calcium to the water, lithium hypochlorite (liquid chlorine) will not. For this and other reasons, it is much more expensive. It dissolves more efficiently, but in reality, you won’t even need to dissolve it beforehand. You can add it directly to the pool water since it’s already in liquid form. Like cal hypo, you should add the shock at night and wait at least eight hours before reentering the pool.

Note: Lhium hypochlorite pool sanitizer is tough to find due to a short supply of lithium.


Out of the three main types of pool shock, dichlor is the easiest and safest to use. Dichlor (also known as sodium dichlor) is a granular pool shock that usually contains between 50-60% chlorine. It can be an excellent solution for both shock treatments and standard chlorine doses. Another superb feature of dichlor is that you do not have to dissolve it beforehand. Just like the other two mentioned products, dichlor must also be used after dark and sit for at least 8 hours.

In The Swim Chlorine Shock Granules (Dichlor)
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What About Non-Chlorine Shock?

Another option that you can use is non-chlorine shock. For more information on how to use it, please check out my guide on non-chlorine shock.

Why You Need to Shock Your Pool

Chlorine’s use in swimming pools is a double-edged sword. Pool chlorine is designed to eliminate dangerous bacteria in the water, making it safe for humans to swim in. But it will also attach itself to ammonia in the pool, producing dangerous chemicals called chloramines. The chlorine levels will fluctuate depending on the number of people who use your swimming pool.

Ammonia is a product of sweat, urine, fertilizers, sunscreen lotions, bird droppings, and other contaminants that find their way into the pool. If you want a clean pool, you must break the chlorine bond (chloramine) by shocking it.

When to Shock Your Pool and How Often

Shocking your pool is not a one-time thing. It should be a regular part of your swimming pool maintenance routine. I recommend keeping a record or logbook near your pool to stay on top of this maintenance. In general, I recommend shocking your pool once a week, especially during seasons when your pool is getting heavy use.

If you need to shock your pool between your standard stocking schedule, consider using a non-chlorine and chlorine shock.

It is important to note that you can also over shock your pool. Yes, there is such a thing as too much of a good thing! Head to my article on adding too much shock to your pool for more information.

So what are some specific circumstances when you must shock the pool?

Rain and thunderstorms can contaminate the water with debris, dust, and excess rainwater. This is why you should always shock your pool after rain.

Algae outbreaks are also a key signal that it is time for a pool shock. When algae blooms begin to appear, you should be vigilant and shock your pool before a major infestation occurs.

Pool parties can also introduce a lot of new contaminants to your pool water. You may want to shock or even double-shock your pool right after a big event.

You should also make sure to shock your pool when opening and closing for the season. After you have balanced the other chemicals, shocking the pool will eliminate bacteria and make the water nice and clear. Read my research on how much shock you need to open your pool for more information on this process.

How to Shock a Saltwater Pool

First off, it’s perfectly okay to shock a saltwater pool. All saltwater pools contain chlorine; it’s just generated by the filter system and doesn’t need to be manually added to the pool.

So, you can use pretty much the exact same process I outlined above to shock your saltwater pool. However, I recommend that you stick with dichlor or non-chlorine shock. I recommend these two pool shock types instead of the usually-popular cal hypo because the higher chlorine content of cal hypo can easily throw off the chemical balance of your saltwater pool and over-chlorinate it. Due to its calcium content, cal hypo is also known to create scaling problems in saltwater pools.

Remember that when shocking your saltwater pool, you should turn off your saltwater chlorine generator (SCG), as the excess chlorine can easily damage your salt cell.

As with traditional chlorine pools, you should shock your saltwater pool every week or every two weeks, depending on the amount of usage your pool gets.

Some saltwater generators have “super chlorinate” options which increases the amount of chlorine in your pool. In other words, you can shock your pool by switching to this option on your SCG.

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Pool Shock Safety Tips

When cleaning your pool, you will be in constant contact with hazardous chemicals, so it is important to follow the necessary safety precautions. Here are my top safety tips when shocking your pool:

  • Check the labels on your shock products to ensure proper storage.
  • Wear protective gear when handling the chemicals. Pool shock can cause chemical burns on the skin and damage your eyes. Gloves and eyeglasses are absolute necessities, but you should also wear long sleeves and pants to prevent contact with your skin.
  • Don’t mix pool shock types! You should never mix chemicals in general, but mixing different types of pool shock can have an explosive reaction. Add all chemicals separately to your pool.
  • Don’t add shock through your pool skimmer or chlorinator. Instead, pour the shock along the edges of your pool.
  • Wait the necessary time before allowing anyone into the water (about 24 hours).
  • Always test your water before jumping back into the pool after shocking. The chemical balance in the pool must be optimal before swimmers hop in.
  • Follow the manufacturer’s instructions. Always check the label, and ensure you are using the pool shock exactly the way the manufacturer intends.

Frequently Asked Questions

What’s the Difference Between Pool Shock and Chlorine?

Shock and chlorine share some active chemicals. However, shock is much more potent than traditional pool chlorine for everyday use and is used for a different purpose – to release combined chlorine and eliminate bacteria. You can read more about the similarities and differences in my article on pool shock vs. chlorine.

Can You Shock a Pool Without the Pump Running?

Technically, yes, you can shock a swimming pool without your pump running, but I don’t advise it. Your pump helps circulate the shock around the pool water to do its job. Without it, you risk your shock being ineffective, and it can cause cloudy water and damage to plaster and equipment.

Can You Shock a Pool After Adding Baking Soda?

Yes, it is perfectly safe to shock your swimming pool after adding baking soda. It will also help balance out the pH level of your pool water since baking soda is very alkaline.

Shock Consistently; Your Clean Pool Will Thank You

Although not too complicated, there is a process to follow when shocking your pool. Once you carefully run through the pool shock instructions a few times, you will soon be a maintenance professional who keeps your pool safe and clean! You must decide on a quality pool shock product or two that fits your needs and then nail down a consistent pool maintenance schedule.

Still need some advice on how to safely and properly shock your swimming pool? Feel free to reach out to me! I am always happy to give a fellow pool owner some expert advice.

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