Last Updated: December 26, 2021

How Many Chlorine Tablets Per Week Should I Add To My Swimming Pool?

Written By: Pool Care Guide
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The below table represents the number of chlorine tablets that you will need per week according to the gallon capacity of your pool.

Swimming Pool Capacity (Gallons)1" Chlorine Tablets (Per Week)3" Tablets (Per Week)
5,000 Gallons1 Chlorine TabletN/A, Too much chlorine
10,000 Gallons2 Chlorine Tablets1
15,000 Gallons3 Chlorine Tablets2
20,000 Gallons4 Chlorine Tablets2
25,000 Gallons5 Chlorine Tablets3
30,000 Gallons6 Chlorine Tablets3

Swimming pools come in an assortment of shapes, sizes, and designs. So, it might seem impossible to know how many chlorine tablets to add per week. However, with a little bit of swimming pool smarts, you can figure out the correct answer for you and your pool. 

There are a few steps to getting the correct answer, so let’s quickly look at chlorine tabs in general, and then we’ll get started with how many to add and when. 

What’s a Chlorine Tablet?

A chlorine tablet often looks just like a hockey puck, about three inches in diameter, only white instead of black. You might also find tablets in one- and two-inch diameters, and sometimes you’ll even see some that are shaped like sticks or smaller nuggets. 

The idea is that as the tablets dissolve in the water, they provide a steady dose of chlorine’s sanitizing power, keeping your water safe to swim in. Tablets also often contain other chemicals, like chlorine stabilizers (cyanuric acid), that help to keep chlorine in the water longer. 

Tablets usually come in two forms: Dichlor or Trichlor. They are both acidic, especially Trichlor. So using them may affect your pH readings. Use the manufacturer’s instructions to figure out what percentage of the tablets are chlorine compared to the rest of the ingredients. 

For instance, if you have a four-ounce tab that’s 65% chlorine, it will have 2.6 ounces of chlorine and 1.4 ounces of other chemicals. That information can come in very handy later down the road, especially if you need to use other chemicals to balance or sanitize the pool’s water.  

How to Use Chlorine Tablets

If you follow these steps, there won’t be any mystery to using chlorine tablets in your pool. And that means your pool will stay clear and ready to enjoy all season long. 

What Is the Volume of Water in Your Pool?

Determining the size of your swimming pool is the first question you have to answer before you can add chlorine to your pool. If you don't know your pool's volume, you can find it by multiplying the square footage volume of the pool and multiplying that square footage by 7.48. You multiply the square footage by 7.48 because 7.48 gallons fit into a square foot. You can make this calculation manually, or you can use our pool volume calculator.

If you already know the volume, you can just move on to the next step.

Figuring How Much Chlorine to Add

The best rule of thumb for pool owners trying to estimate how many tablets to add is this:

Add one tablet for every 5,000 gallons of water and always round up. For example, if your pool has 21,000 gallons of water, add five tablets per week. If it has 8,000 gallons, use two tablets. 

If you add chlorine tablets on the same day weekly, you’ll always have a consistent level in the water, as the tablets dissolve pretty slowly. 

Adding the Tablets

There are a few different ways to add the tablets to the pool. It’s really up to you as the pool owner to decide what’s easiest and most practical. 

Inline Chlorine Canister

Many pools have an automatic chlorinator built into the plumbing. This allows you to add tablets to the water very easily. Just shut off the filter system, unscrew the canister’s lid, add the tablets, and close it back up. Now, when you turn the system back on, your water will pass through the plumbing and receive a dose of chlorine. 

Chlorine Floater

Not every pool has an inline chlorinator. So, you can also purchase a simple floating canister that allows you to add chlorine to the water. The canister sits inside of a floating plastic ring. Simply unscrew the canister’s lid, add your tablets, seal it back up, and let it float on the surface.

Make sure that the floater doesn’t sit in one place for too long, as you could end up with a stain from having too much chlorine concentrated in one place. 

Add Tablets to the Skimmer

You can also add your chlorine tablets right to the skimmer. Just make sure that you empty the skimmer basket before adding more tablets. And, if any of the last week’s tablets are remaining, save them and add them back to the basket along with the new ones. 

What’s the Chlorine Reading in Your Pool?

Even though a weekly dose of tablets is a good estimate, the amount of chlorine your pool needs can vary pretty wildly. That’s because factors like weather, how many swimmers you have, how much splashing they do, and how much aquatic life is trying to live in your water can all influence how fast the chlorine in the water gets used up. 

If you don’t have enough chlorine to meet the demand, the water won’t stay clear and sanitized, and a green, cloudy pool is not just an eyesore. It’s also unsafe to swim in. 

For instance, if you have a pool that typically sees only a few swimmers in a given week, and you suddenly have a major pool party with fifty people swimming, you’re going to need more chlorine than usual. 

Every pool owner should have a means of checking their water's chemistry and chemical content. That will mean having a bottle of pool test strips on hand for most. Those who prefer more exact readings might choose to have a water test kit instead.

A test kit is much more complicated to use, though it is a bit more accurate. For most owners, test strips will be the way to go. 

Instructions might vary a bit between brands, but all you have to do is slip the dry test tube into the water about 6 inches below the surface. The little squares on the strip will change colors when you take it out. The colors will correspond to a chart on the bottle of strips, giving you readings for a few chemicals. 

Some strips might only show readings for free chlorine and total chlorine. Those are the ones we really need to know for determining how many chlorine tablets to add. But, you might also end up finding readings for pH, cyanuric acid, total alkalinity, hardness, and more. 

Once you have a reading of free chlorine and total chlorine in the water, you can use that information to see how much chlorine your pool needs to reach the minimum levels. Your test strip package might have a good guide right on the bottle. 

Sometimes, a pool calculator is the easiest way to determine exactly how much chlorine to add. These handy online tools ask you to enter the values from your test strips, the volume of water in your pool, and some other information. Then, with the click of a button, it tells you how much chlorine to add to get your pool sanitized. 

How Many Tablets per Week, Bottom Line

Whichever method you use, it's important to check the pool regularly. The more you commit to a routine of maintenance, the better you’ll be able to enjoy your swimming pool. If you slack off for a couple of weeks and don’t keep up with your basics, don’t be surprised if you walk into your yard to find a green pool. 

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