How Much Bleach Do I Need to Shock My Pool?

Many people may wonder if it’s possible to shock your pool with bleach instead of liquid chlorine. The answer is yes–you can use store-bought bleach, but the amounts you use will be different, as household bleach and professional liquid chlorine are not the same concentration. 

However, how much bleach to add isn’t the only part of the equation–it’s also important to consider when to give a shock treatment to your pool. Luckily, we’re here to help you figure out the how and the when.

When to Shock Your Pool

If you’re just opening your pool for the first time this year, it’s a fantastic time to shock it. After all, it’s probably a little green after sitting for so long, especially if you didn’t shock it during the winter months. 

Another great time to shock your pool is after a pool party. Any time your pool gets a lot of use, it can cause a rise in bacteria levels. This is because, despite our best efforts, humans are covered in microorganisms and bacteria that wash off in pools. Once there, they begin multiplying and changing the chemistry of the pool. 

Many people falsely assume that if there is a strong chlorine smell and your eyes are burning, it’s because your chlorine levels are too high; in reality, the levels are too low. The cause of the chlorine smell is that the chlorine in your pool has stopped bonding with the water and started to bond with the bacteria instead. This creates a chemical known as chloramine that gives off that terrible smell and makes your eyes red. For this reason, for heavy-use pools, it’s not a bad idea to shock your pool every week or two. Other causes of chloramine formation include heavy rain and extended periods of hot and sunny weather.

Lastly, shocking your pool isn’t just about how often, but also at what time of day you do it. The UV in sunlight causes chlorine to quickly break down before it has a chance to bind and mix with the water, so you should always shock your pool after sunset and set your pumps on high to allow the chlorine to mix with the water before the sun comes up. 

How Much Bleach to Use

When it comes to how much liquid chlorine to shock a pool, we recommend using one to two gallons of 12.5% chlorine per 10,000 gallons of water to properly shock your pool. Store-bought bleach is much weaker in chlorine concentration, though—typically around 6%—so, you’ll need to use double that amount. Two to four gallons of bleach per 10,000 gallons of water should do it. Whether or not this is more or less expensive than using professional 12.5% chlorine depends on which brands you’re using. 

All this being said, be absolutely sure you read the label on your bottle of bleach before adding it to your pool, as some have more chlorine and some have less. For example, if your store-bought chlorine is 8% instead of 6%, you’ll only need 1.5 times as much instead of double. 

In case you need to know how much shock is needed for a green pool, double the amount is best. For dark green pools, you can use three of four times the amount of 6% bleach per 10,000 gallons. 

The Aftermath

After you’ve shocked your pool, the pH levels are going to spike. Because of this, you’ll want to wait a full twenty-four hours and test the pH levels in your pool before going for a dip. 

The ideal pH for a swimming pool is around 7.2 to 7.8, so you can aim for the middle at 7.5. If your pool’s pH is still high, you can add chemicals to lower the pH. If the pH level is too low, you can add another gallon of bleach and wait another twenty-four hours. Always remember to wear gloves when handling pure bleach, and if any bleach gets on you, rinse it off with plenty of water right away. 

In Summary

Pool care doesn’t have to be complicated, and it doesn’t have to be expensive. Do the math to make sure you get the levels correct, and there’s no reason you need to use high-end liquid chlorine, as long as you do it right.