Trichlor Chlorine: Should You Use It for Your Pool?

Written by Michael Dean
June 12, 2024

trichlor chlorine next to swimming pool

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. Trichlor is one of these options.

So, what exactly is trichlor, and is it a good idea to put it in your pool? Let’s dive in.

Main Takeaways

  • Trichlor is a stabilized chlorine, meaning it contains cyanuric acid.
  • Trichlor is highly effective and easy to work with, but it cannot be used to shock a pool.
  • You should use 1 tablet of trichlor for every 5,000 gallons of water.
  • Don’t use trichlor if you already have low pH 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 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 most 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 difficulty 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 determine 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.

I recommend using one tablet for every 5,000 gallons. Therefore, most residential pools will receive 1-3 tablets once per week. You can use my chlorine calculator for more precise calculations and read my advice on the recommended frequency of adding chlorine to your pool.

In The Swim 3 Inch Stabilized Chlorine Tablets

These basic trichlor tablets are perfect for most swimming pool owners.

View on Amazon View on Walmart
I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

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 increase 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 reliable alternative such as calcium hypochlorite or liquid chlorine. I go over this major difference in more detail in my pool shock vs. other types of chlorine article.

Other Alternatives

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


Dichlor, an abbreviation of the 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%.

I have a lengthy comparison of dichlor vs. trichlor where I cover all the major differences and which chlorine type you should choose, which depends on your situation.

Clorox Pool&Spa Pool Shock XtraBlue

Clorox makes a good dichlor-based pool shock that contains zero cyanuric acid and helps fight contaminants.

View on Amazon View on Walmart
I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

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.

Champion Pool Shock Liquid Chlorine (12.5% Concentrated Strength)

This shock from Champion is an easy-to-use liquid chlorine perfect for getting rid of algae and cloudy pool water.

View on Amazon View on Walmart
I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

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 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 switching from one to the other. You can read my complete comparison of trichlor and calcium hypochlorite for more information on their differences.

In The Swim Calcium Hypochlorite Chlorine Granular Pool Shock

In The Swim has a reliable cal hypo shock that is effective and easy to use.

View on Amazon View on Walmart
I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

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.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

Something went wrong. Please check your entries and try again.

Trichlor Is a Reliable Chlorine Option

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.

Scroll to Top