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The Best Chlorine Tablets for Your Pool (and How to Safely Add Them)

By Matt Giovanisci | Updated: March 22, 2023

Chlorine tablets are one of the most convenient, hands-free ways to sanitize your pool. Unlike liquid chlorine or granular chlorine, chlorine tablets (also known as chlorine pucks) dissolve slowly over time. Coming in two sizes (either 1-inch or 3-inch pucks), chlorine tablets are pre-dosed and already contain a chlorine stabilizer (a.k.a. cyanuric acid or CYA).

If you have a larger pool that’s over 5,000 gallons, you’ll want to use 3-inch chlorine tablets.

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3-Inch Stabilized Chlorine Tablets

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But if you have a smaller pool, like an Intex pool or a pool 5,000 or less, you’ll want to use 1-inch chlorine tablets instead. While technically you can use a single 3-inch puck for 5,000 gallons of water, it’s easy to accidentally over-chlorinate if your tablets are too large.

In the right applicator, like an automatic chlorinator, chlorine tablets provide a steady supply of chlorine to your pool water. And they’re easier to handle and store than granular or liquid chlorine.

But there are some downsides to chlorine pucks. They can drastically lower your pH and alkalinity levels, which can irritate swimmer skin and eyes and erode pool surfaces and equipment. They can also raise your cyanuric acid levels over time since each puck is stabilized. And high cyanuric acid levels can impact your chlorine’s effectiveness. It all depends on what chlorine tablets you use, how you add them to your pool, and how often you test your water.

So here’s how to choose the right chlorine tablets based on your pool size and how to add them safely.

What’s the Difference Between Chlorine Tablets and Other Types of Chlorine?

Pool chlorine comes in three common forms: tablets, granules, and liquid.

The ideal chlorine level in your pool: Your free chlorine levels should be 1 to 3 PPM (parts per million), with 3 PPM being ideal. Even if you use slow-dosing chlorine tablets, you’ll want to test your pool water once per week to make sure your pH, alkalinity, and chlorine are within range. The wrong chlorine levels can cause eye and skin irritation, algae growth, or cloudy water.

If you’re still feeling confused about water chemistry and how to add chemicals to your pool, check out our Pool Care Video Course. It’s a step-by-step guide to help you keep your water balanced and sanitized (without overcomplicating things).

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How to Choose the Right Chlorine Tablet Size: 3-Inch vs. 1-inch

Tablets typically come in two sizes: 3-inch or 1-inch chlorine tablets. As a general rule, one 3-inch tablet will sanitize 5,000 gallons of pool water.

One-inch tablets dissolve more quickly since they are smaller and have less surface area for the water to pass over. They’re great for smaller pools. While you technically could add a single 3-inch puck to a 5,000-gallon pool, it’s easy to over-chlorinate a smaller body of water. Using multiple 1-inch tablets is a better way to control dosing.

Three-inch tablets, on the other hand, are easier to handle and dissolve more slowly than 1-inch tablets. They’re better for larger pools since a single 3-inch tablet can sanitize up to 5,000 gallons. And they’re the best size to use in an automatic chlorinator.

Our Top Pick
Hayward Automatic Pool Chlorinator (Inline)

This automatic chlorinator is perfect for the pool owner who hates fussing with chlorine tablets. With its dial control valve, you can easily adjust the chlorine level depending on your pool's size.

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While this is a more hands-off approach to sanitizing your pool, you’ll still have to regularly measure your water chemistry levels. Remember, chlorine tablets can lower pH and alkalinity levels and raise your cyanuric acid levels over time.

If you don’t already know how much water your pool holds, check out our easy-to-use pool calculator to figure out your pool volume.

Pool Volume Calculator Click on your pool shape to calculate the volume of water.
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How to Choose the Best Chlorine Tablets for Your Pool

Regardless of the brand you choose, most chlorine tablets are made of trichlor chlorine. Containing up to 90 percent chlorine, solid trichlor chlorine tablets also contain cyanuric acid (CYA) that stabilizes the chlorine and protects it from breaking down in the sun. Once a tablet dissolves in the pool water, the treatment resists degradation under direct sunlight and UV light, slowing the production of chloramines.

Most chlorine tablets contain the same ingredients, so you won’t see many variables across brands. But be sure to double-check the ingredients and the size of the tablets (1-inch vs. 3-inch). And make sure that your chlorine pucks come in a properly sealed container or bucket. Some chlorine tablets come individually wrapped inside the containers as well.

Do not use chlorine tablets if you have an indoor pool! Chlorine tablets contain cyanuric acid to protect chlorine from breaking down in the sun. But it will build up over time in an indoor pool, and indoor pools do not need any CYA.

How to Add Chlorine Tablets to Your Pool

There are three common ways to use pool tablets: using an automatic chlorinator, inside a floating dispenser, or placed in your skimmer basket. Keep in mind that other things like your pool water temperature and water pressure can impact the amount of time it takes your tablet to dissolve. And a larger, 3-inch tablet will break down more slowly than a 1-inch tablet. We recommend using an automatic chlorinator or a floater for your chlorine tablets.

floater-vs-skimmer-vs-chlorinator

Our Top Pick
Hayward Automatic Pool Chlorinator (Inline)

This automatic chlorinator is perfect for the pool owner who hates fussing with chlorine tablets. With its dial control valve, you can easily adjust the chlorine level depending on your pool's size.

Buy Now On Amazon
If you click this link and make a purchase, we earn a commission at no additional cost to you.

Whenever adding chlorine tablets to your water, be sure to test and balance your other chemical levels. Make sure your alkalinity is between 100 and 150 PPM and your pH is between 7.4 and 7.6. Your alkalinity will impact your pH, and your pH can impact the effectiveness of your chlorine. Also, be sure your cyanuric acid levels should be between 30 and 50 PPM. Adding chlorine tablets to your pool water increases your CYA levels.

If you need more help with pool chemistry, check out our guide on Basic Pool Chemistry 101.

How Many Chlorine Tablets Should I Use in my Pool?

A 3-inch chlorine tablet can sanitize up to 5,000 gallons of water. So if you have a 20,000-gallon pool, you’ll want to use four 3-inch chlorine tablets. To calculate the right number of tablets, round your pool volume up to the nearest 5,000 gallons. And if you have a smaller pool (under 10,000 gallons), consider using 1-inch chlorine tablets. It’s easy to over-chlorinate a smaller body of water.

Check your automatic chlorinator or floater each week and test your water chemistry using a test strip or liquid test kit. Balance your pH and alkalinity and monitor your chlorine and cyanuric acid levels. If your chlorine or CYA are too high, you’ll need to use less chlorine tablets or adjust the settings on your dispenser. Refill your dispenser with chlorine pucks as needed each week.

Matt Giovanisci is the founder of Swim University® and has been in the pool and spa industry since 1995. Since then, his mission is to make pool and hot tub care easy for everyone. And each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
A Cheat Sheet For Perfectly Balanced Pool Water and Crystal Clear Swimming
Download this FREE printable cheat sheet to keep your pool clean and clear without any fuss. You’ll never worry about your pool again with this easy-to-use guide.
Click Here For The FREE Cheat Sheet