How Much Liquid Chlorine Do I Need to Shock My Pool?

Are you opening your pool for the first time in the late spring after not using it all winter? Is the water cloudy? Before you use it, you’ll probably want to shock your pool to ensure it has the proper pH level and any algae or bacteria are destroyed. 

But how much chlorine should you be using, and how often do we need to shock a pool? The answer to both of these questions depends, but we’re here to help you understand when it’s time to shock and how much chlorine to use. 

When to Shock

For the best pool shock results, it’s recommended that you shock your pool at least once before using your pool for the first time in the warmer months, and at least once after the last time you use the pool, before the winter months. 

Other times that are good to shock your pool are when you notice a strong chlorine smell. Contrary to popular belief, a strong chlorine smell is actually a sign that the chlorine in your pool has stopped mixing with the water and begun to bind with other bacteria in your pool and become what is known as chloramine. Chloramine is what gives the water that strong smell and burns your eyes. 

For heavy-use pools, you can shock your pool once a week or every two weeks. Alternatively, if you threw a big pool party last week, there’s a decent chance all that skin bacteria your guests had on them is now in the pool and binding with the chlorine, so it might be advisable to shock your pool. 

Other times to shock are after extended periods of hot and sunny weather when bacteria can build up due to warm conditions, and after heavy rains which can dilute your water and introduce other types of bacteria. The time of day you shock your pool is also important–it’s not advisable to shock your pool in the daytime, as UV light breaks down the chlorine. It’s best to shock your pool after sundown so the chlorine has time to bind with the water, kill off the bacteria, and level out the pH. 

If your pool has gone green and has algae buildup, it’s a good idea to clean the pool of all that debris and gunk before shocking it. 

How Much Liquid Do I Use?

How much chlorine you need to use is going to be determined by the size of your pool. More water requires more chlorine. Generally speaking, you should aim for one to two gallons of 12.5% liquid chlorine per 10,000 gallons of water. You can try one gallon first and see how it goes before you decide to add that second gallon. For highly-green pools, go ahead and just use two gallons. Be sure to wear gloves and be careful not to splash the liquid pool shock on yourself. If you get any on your skin, rinse it off quickly with lots of water.

After shocking your pool, you should wait for at least twenty-four hours before swimming in it. Adding all that chlorine is going to cause the pH level in your pool to spike, and it will take around a day before the pool’s pH level comes down to normal. Always test your pool’s pH to make sure it’s at roughly 7.5 before going for a dip. 

If it’s still high, you should wait another day or try adding baking soda to lower the pH level. You can shock your pool after using baking soda—it won’t cause a reaction because the levels are too low in such a large amount of water. If your pH level is still too low, you can add some more chlorine in the evening, and try again after waiting another twenty-four hours. 

For those wondering how much bleach to use to shock a pool, the calculation is different because bleach and pool shock chlorine contain different percentages of chlorine, so be sure you understand how much chlorine is in the bleach you’re using.

In Conclusion

Using chlorine properly is an important part of keeping your pool clean and ensuring it has a long life. By following these simple tips, you can make sure you have the perfect pool for swimming for years to come.