How to Properly Chlorinate Your Pool—In Three Easy Steps

Picture the ideal swimming pool. It might have Spanish tiles, a high diving board, some sleek and unique ladders, maybe even a fountain. Everyone has their own style, and that’s part of what makes the industry great. But I bet the one common aspect everyone shares in their ideal image is this: a sparkling clean pool. And I’m talking sunlight-reflected-in-diamond-shapes clean.  

Other than just being nice to watch, water that’s truly free of dirt and grime is also free of bacteria, including the kind that can make you sick. So not only does it look nice to have a clean pool, but it’s the only safe way to swim. You can skim and vacuum your pool, have the right pool pump, and run it for the perfect amount of time every day—as you should. But chlorine is the only thing that will kill that nasty bacteria on a microscopic, continuous level. I’ll explain what chlorine is, how it works, how to choose the right kind and amount for you, and how to properly add it to your pool—all in three easy steps. Let’s get sanitizing.

First Thing’s First: What Exactly is Chlorine?

Chlorine is basically a household name—and for a reason. It’s by far the most popular pool sanitizer, mainly because it’s both wildly effective and wildly inexpensive, a combination anyone should love. It’s also exceptionally safe, as long as the dosage is right. It’s even used for drinking water when dosed down. Basically, if you’re in the ballpark of the right amount of chlorine for your pool, you’ll kill all the bacteria you need to and won’t irritate your skin, eyes, and throat.

Chlorine is a chemical compound—but that doesn’t mean you had to have aced high school chemistry class to understand it. The solid form of chlorine is sodium hypochlorite, and the liquid form is calcium hypochlorite. And despite popular misconception, you don’t need a different type of chlorine for an above ground versus in-ground pool. Sound good? Let’s move on.

Interested in busting dirt and debris from your pool as well as well as microscopic bacteria? You should be. Try the Blue Torrent MyBot In-Ground Robotic Pool Cleaner: it’s the most economical, high performance pool cleaner on the market—and comes with a lifetime warranty. According to customer David Lain, “Very pleased. My wife loves it.”

How Does Chlorine Ensure Safe Swimming?

This one is pretty simple: when added to your pool properly, sodium hypochlorite (or calcium hypochlorite, if you prefer liquid chlorine) inactivates the bacteria in your water. This doesn’t mean that the bacteria is technically completely removed—you’ll need the right pool filter and the help of pool shock for that—but the bacteria will be dead in the water. (You have no idea how long I’ve been waiting to use that phrase.)

Step One to Proper Chlorination: Choosing the Right Chlorine.

This is where it gets technical. The ideal chlorine combination of your pool is between 1 and 3 parts per million (ppm). In order to kill pathogenic viruses, you’ll want to make sure your chlorine concentration doesn’t fall below 1 ppm. Go above 3 ppm and while you’re sure to wipe out bacteria, you’re also vulnerable to that irritation in your eyes, nose, lungs, and throat. Now that you’ve got the numbers, it’s time to choose between stabilized or unstabilized chlorine for your pool—and trust me, it won’t take more than sixty seconds to find out. 

Choosing Chlorine: Is Stabilized or Unstabilized Right for My Pool?

It’s simple: pool chlorine is either stabilized or unstabilized. True, the idea of unstabilized chlorine might bring to mind lab coats, beakers, and minor explosions. But in the case of chlorine, “stabilized” only means that it contains a chemical called cyanuric acid. Cyanuric acid shields chlorine from the sun like a sunscreen but is actually, uh, reliably effective. Who else has already gotten roasted this summer?

Stabilized chlorine is the most popular, because most pools are outdoors. If you have an outdoor pool, you’ll want stabilized chlorine, or your chlorine will break down and prove itself more or less completely ineffective. If you have an indoor pool, you can use stabilized and unstabilized chlorine no problem. You also have pretty sweet digs—I’m jealous.

Is your chlorine not circulating because your pool water moves too slowly? Your horsepower might be too low for the job your pool presents. Try a more powerful unit like this Blue Torrent 1.5 HP Typhoon In-Ground Pump. According to customer Thomas Van Strander, “You can not beat this value. It is soooo quiet.” 

Choosing Chlorine: Which Type is Best and How Much Do I Need?

Although outdoor pool owners have the option between granules of chlorine and chlorine tablets, tablets are the way to go—and most maintenance experts agree. Why? Well, they’re cost-efficient, they dispense chlorine at a steadier rate, and they’re simply the easiest to use. It’s a no brainer.  

Chlorine tablets come in one-inch and three-inch sizes. For most pools, the three-inch size is recommended, since they are less complicated and cheaper to use—they sanitize a whopping 5,000 gallons per tablet, and you can use fewer of them than you would one-inch tablets.

If you have a spa or a very small pool—in other words, any body of water less than 5,000 gallons—the one-inch tablets are for you. They might also be handy for very, very large pools because of their faster rate of dissolution, but it’ll cost you. 

Not sure how many gallons of water your pool contains? It’s simple geometry anyone can do—even if you weren’t exactly a candidate for math camp that year. You just have to multiply the length, width, and depth of your pool in feet, and then multiply that figure by 7.5 to convert the number to gallons. Prefer formulas? Follow the one below:

[Pool Length in Feet] x [Pool Width in Feet] x [Pool Depth in Feet] x 7.5 = [Volume of Your Pool in Gallons]

For the purposes of finding how many tablets your pool needs, round your volume up to the nearest 5,000—so you can be sure you’re not undershooting it. If your pool has a capacity of 25,000 pounds, you’ll want to use five tablets (that’s one tablet for every 5,000 gallons). If only algebra class was always that easy.

Step Two to Proper Chlorination: Adding Chlorine to Your Pool.

I wish it was as simple as tossing the chlorine tablets into the pool and letting them take care of the rest—it’s not. Thankfully, there are a few devices that will ensure your chlorine is disseminated throughout your pool water—and active traces of bacteria are long gone.

Make a long term decision with the Energy Star Variable Speed In Ground Pool Pump. It’s ultra quiet, guarantees you’ll save big on your energy bill, and is eligible for rebates. But there’s more: it also comes with a lifetime warranty.  

The Floating Chlorine Dispenser.

If you grew up around pools, you most certainly remember swimming around this floater—and accidentally kicking it during your underwater flips. Unfortunately, nostalgia is where our warm feelings for floating chlorine dispensers should end. This low-maintenance and fairly inexpensive device—you can get one for as little as ten dollars—proves that sometimes you get what you pay for. Womp womp.

What’s the problem with floating chlorine dispensers? Well, they’re just not consistent. If they get caught in one place—which they often do—they can release too much chlorine in one area of your pool (which can also destroy your pool liner). They release chlorine into more or less slow-moving water—not the water that flows directly through your pool filter as part of the circulation of your larger system. This means that the chlorine dispensed is not spread evenly throughout your swimming pool. And if it’s not dispensed evenly, it’s not effective. Skip this nostalgic device and read on.

The Pool Skimmer.

Much better than the floating chlorine dispenser—and if you can believe it, even cheaper to start—is the pool skimmer method. In this case, you really can drop in chlorine tablets and call it a day. The caveat is that you’re dropping the correct amount of tablets into your pool skimmer, which looks like a little basket-lined bucket and is built into the side of the pool. Make sure your pool filter is on, and add in the tablets to push beautifully-sanitizing water through your return jets, which will spread chlorine evenly throughout your pool.

Of course, although this method doesn’t require buying anything but the tablets, it’ll cost you in energy costs to run your filter. My recommendation? Make a long-term investment that’ll save you significantly. Variable-speed pumps like this Energy Star-certified model have the option of running at a lower speed, and tend to pay themselves off in under a year in energy saved. It’s my top recommendation for any pool owner. 

The Automatic Chlorinator.

Meet the most sophisticated chlorinating device on the market. The automatic chlorinator hooks up to your return line (that’ll be the plumbing that runs from your pump back to your pool) to ensure the water is sanitized just before it enters the pool. A favorite of pool maintenance experts, it allows you to load the feeder with tablets in bulk, without worrying about how many. You then set it for a chlorine level of 1 ppm to 3 ppm and let it do the work.

Here’s a tip: in the beginning, make sure you use chlorine test strips to make sure that the level you set is accurate for your specific variables: your environment, how frequently the pool is used, and the natural water quality of your area. These details matter, and it’ll save you the headache later.

Step Three to Proper Chlorination: Pool Shock.

If you don’t know about pool shock already, now is the time to learn. Pool shock is technically a higher dose of chlorine, and its weekly use is absolutely essential to a clean pool.

Here’s how it works. After a chlorine particle attacks and kills bacteria or another organic material in your wall, it creates what we call a chloramine. This is an inactive particle that exists in your water until it can be broken apart by oxidation. But not only is it kind of gross, it also reduces the amount of free chlorine in your pool—that’s the amount that your chlorine can actually work. So if you only chlorinate your pool, without shock, your chlorine will become increasingly less effective. Cue swamp scenario.

Pool shock is super easy to use: just walk around the perimeter of your pool and pour the right amount in. Just remember to add shock at dusk or at night, or the sun will burn out the compound that makes it effective.

Looking for an extra-reliable dose of pool shock? Try this Super Premium Sanitizing and Fast-Acting Pool Shock, which is reasonably priced, conveniently packaged, and gets the job done. According to customer Sally Nield, “very fast and good.”

Chlorination Done? Now Start the Real Fun.

When it comes to your pool, the reward far outweighs the work—and it’s even better when you take the DIY approach and worry less about the cost. Now that you’re checking your levels twice a week with test strips and adding chlorine accordingly, you can forget about bacteria and focus on the fun. No matter what, a clean pool is a luxury you earned. Enjoy it.


This article explains how you can backwash your pool filter efficiently. Want to know how to clean the bottom of your pool? Read more here.

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