Trichlor Chlorine: Should You Use It for Your Pool?

When it comes to maintaining your pool’s delicate chemical balance, even small mistakes can have significant consequences. That’s why it’s vital to make sure you’re using the right chlorine.

There are many different kinds of chlorine out there, and all of them market themselves as pool owners’ first and best line of defense against germs and other unwelcome guests. Trying to find one you can rely on to keep your swimming pool clean and safe can feel like a bit of a gamble. They can’t all be the best — right?

Trichlor is one such product. What exactly is it, and is it a good idea to put it in your pool?

What Is Trichlor and How Does It Work?

“Trichlor,” short for Trichloro-S-Triazinetrione (try saying that five times fast), is an ultra-concentrated type of chlorine that usually comes in tablet form. At up to 90% concentration, it contains the most chlorine of any commercial sanitizer aside from gaseous chlorine, which isn’t generally recommended for use in residential pools.

Trichlor’s other main ingredient is cyanuric acid, a conditioner that helps stabilize the chlorine to keep it within a safe level and make it last longer.

Like other sanitizing products, Trichlor’s primary function is to eliminate disease-causing organisms that have a way of turning up in pools and hot tubs, like bacteria, viruses, parasites, and algae. Thanks to its high chlorine concentration, its efficiency in this area is virtually unmatched.

When you place a Trichlor tablet in your pool, it immediately begins dissolving and converting into hydrochloric acid. If you retained anything from your 10th-grade chemistry class, you know that hydrochloric acid is highly corrosive. You can imagine what it does to microbes unlucky enough to try to invade your pool.

Pool owners love the simple, hands-off utility of Trichlor. Chlorine tablets are the sanitizer of choice for tons of pool care specialists.

Pros and Cons of Trichlor

Trichlor offers a multitude of perks for practical pool owners, especially those who don’t relish the responsibility of balancing their pH and performing other routine water care rituals. But it does come with a couple of drawbacks, as well. Let’s take a look at each.


  • Trichlor is a highly effective sanitizer. You can rest assured that the chlorine will kill off unwanted microorganisms without posing a risk to you, your family, or your pets.
  • It’s easy to work with. All you do is place the recommended number of tablets in your chlorine dispenser or automatic chlorinator and go about your day.
  • Pre-portioned tablets spare you the trouble of having to measure out liquid or granulated chlorine.
  • You can use less of it than other forms of chlorine because of how concentrated it is.
  • Trichlor is readily available at any pool supply store, so getting it is never an issue.
  • Tri has a long shelf life—you can buy in bulk without worrying about it losing its potency over time.
  • Trichlor is surprisingly affordable when compared to many other sanitizer products.


  • The increased acidity produced by chlorine tablets can corrode metal particles floating in your pool water, potentially leading to staining or rusting.
  • Trichlor is a volatile chemical and can actually explode if exposed to calcium hypochlorite in high enough amounts. For this reason, you must always handle it with care.
  • Some Trichlor products may introduce too much cyanuric acid into your pool. In excess, cyanuric acid can neutralize the effects of chlorine.
  • Trichlor won’t work for shocking your pool the way other forms of chlorine can.

When You Should Use Trichlor

Trichlor is perfectly safe when used correctly and is an ideal low-maintenance sanitizing solution for the majority of home pools.

That said, it’s most suitable for pool owners who don’t want to bother measuring and proportioning multiple chemicals.

Chlorine tablets can also be a lifesaver for those who have a hard time staying on top of their daily sanitation duties. They take the guesswork out of chlorination, allowing you to turn your attention to more important things.

While you can drop Trichlor tablets directly into your pool, the best way to add them is to use a basic chlorine dispenser or automatic chlorinator. You can frequently find these for less than $100 online or at your local pool supply shop.

To figure out exactly how many tablets you’d need to put in your pool during each weekly treatment, you’ll first need to know how much water it holds.

We recommend using one tablet for every 5,000 gallons. Therefore, most residential pools will receive 1-3 tablets once per week. It’s as easy as that!

When You Shouldn’t Use Trichlor

Sanitizing your pool with Trichlor is never a bad move, but there are some situations where it might make maintenance more complicated.

Think twice about working with Trichlor if your pool already has a low pH. Over time, the cyanuric acid released as the tablets dissolve will drive up the water’s overall acidity. This can present its own set of problems, not the least of which is a drastic decrease in the effectiveness of the chlorine itself.

Acidity is also the leading culprit behind staining and rusting on pool surfaces. Not only can discoloration degrade your pool’s visual appeal, but it can also be very expensive to deal with.

For the same reason, Trichlor doesn’t do very well as a shock. When it comes time to spike the free chlorine levels in your pool, you’re better off going with a faithful alternative such as calcium hypochlorite or liquid chlorine.

Other Alternatives

If for some reason you don’t think Trichlor is the right choice for your pool, you’ll be pleased to know that you have no shortage of alternatives available to you. Other sanitizers worthy of your consideration include:


Dichlor, an abbreviation of active ingredient Dichlor-S-Triazinetrione, is essentially a milder version of Trichlor. Like its more potent counterpart, it comes in both tablet and granular form, but only has an average chlorine concentration of around 55-62%.

Sodium Hypochlorite (Liquid Chlorine)

Sodium hypochlorite is a liquid sanitizer containing roughly 10% chlorine, or about twice the concentration of standard household bleach.

Sodium hypochlorite is an unstable form of chlorine (as are the other chlorine products listed here, except for Dichlor), meaning it requires the addition of cyanuric acid separately.

Calcium Hypochlorite (Cal-Hypo)

Calcium hypochlorite is the most universal type of chlorine used to treat residential and commercial pools. It comes in both granular and tablet form. Cal-hypo is what comes to most people’s minds when they picture pool chlorine.

Remember, Cal-hypo and Trichlor are a bad mix, so be sure to cycle out the water in your pool if you’re thinking about making the switch from one to the other.

Lithium Hypochlorite

Another granular sanitizer with a 33% chlorine concentration, lithium hypochlorite makes an excellent shock. It dissolves quickly and without a trace but tends to cost more than other chlorine products. It also must be added in greater quantities.

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Final Words

Still wringing your hands over the decision of which chlorine to buy?

Relax—pretty much any chlorine-based sanitizer will work just fine for your pool, so long as you’re willing to invest the necessary time and effort into using it properly.

If, like many pool owners, you’re looking for a way to simplify the chlorination process and make routine chemical maintenance one less thing to have to keep up with, however, Trichlor is definitely your best bet.

Any questions? Shoot me a note.

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