Trichlor Chlorine: Should You Use It For Your Pool?


Sanitizer is the most important chemical you will ever use to keep your pool clean and safe. 

Sure, all those others play a factor in balancing it, but without the right sanitizer, you’re fighting a losing battle. In fact, according to the CDC, chlorine is what will protect you and your family from “recreational water illnesses.”

So...add chlorine...sounds simple enough, right?

But not so fast. As soon as you step into the sanitizer aisle at your local big box or pool supply store, you’ll see that choosing a product is not as easy as it sounds. 

You’ll probably see a pretty wide variety of products that contain different types of chlorine, such as Dichlor, Calcium hypochlorite, Sodium hypochlorite, and Lithium hypochlorite.

But the one we will focus on today is Trichlor.

What is Trichlor?

Trichlor is short for Trichloro-S-Triazinetrione, which is a “dry solid containing the highest (90%) available chlorine content of any chlorine sanitizing pool treatment” other than gaseous chlorine. 

Trichlor products usually come in tablet form and are a mix of chlorine and cyanuric acid. And that mix helps to stabilize the chlorine, meaning germs and sunlight won’t use it up as fast.

What is Trichlor Used For and How Does It Work?

Trichlor, of course, is used to kill germs in pools and hot tubs. The tablets dissolve in the water and are converted into hydrochloric acid that attaches to contaminants to break down their cell walls.

Once this happens, the contaminants are unable to infect their surroundings with bacteria and disease. They’re also unable to multiply and cause further problems.

This is the same way other chlorine products work, but because Trichlor is more concentrated, it does a more efficient job than many others.

Trichlor Chlorine for Your Swimming Pool: Pros and Cons

Trichlor is a pretty great product, but before you buy anything you’ll be in such close contact with, it’s important to know all you can about it. First the pros…

Pros of Trichlor

  • It’s about the strongest concentration of chlorine you can buy for your pool. 

  • You can use less of it than other products because of its high chemical content.

  • There’s no measuring. They’re in tablet form, so you just toss the right number of them into the pool.

  • It’s self-maintaining, meaning you won’t have to pour chlorine into your pool every day because they dissolve slowly.

  • It’s affordable and actually one of the least expensive chlorine products on the market.

Cons of Trichlor

  • It can raise CYA (cyanuric acid) levels too quickly, which can actually reduce the effectiveness of the chlorine.

  • It’s a volatile substance that is potentially explosive if mixed with cal-hypo (calcium hypochlorite). 

  • It can rust or stain your pool surfaces and equipment if not used correctly.

Trichlor Chlorine Alternatives

Like we talked about earlier, there are lots of different chlorine products you can use for your pool. But Trichlor and Dichlor are the only ones that are stabilized, meaning they contain CYA.

If you use unstabilized chlorine, you can always add CYA, but you’ll have to measure carefully and keep up with one more chemical. That being said, some people prefer using something a little milder for their home pools.

Sodium Hypochlorite

Sodium hypochlorite comes in liquid form and contains about 10% available chlorine. Household bleach contains this substance but in a much milder concentration of 5% available chlorine.

This is effective for cleaning surfaces but not for disinfecting your pool.

Calcium Hypochlorite

This product, commonly known as Cal-hypo, usually comes in granular form but you will sometimes see it in tablets as well. It contains between 40 and 80% available chlorine and is probably the most popular.

Cal-hypo is what you will usually find in pool shock and many other sanitizing products.


Dichlor (or Dichlor-S-Triazinetrione) is the other chlorine product you can buy that contains its own appropriately-measured dose of CYA. You can get Dichlor in granular or tablet form.

Dichlor typically has a little less available chlorine than trichlor at around 55-62%, so it’s a little milder. But like Trichlor, it is also a volatile substance.

Lithium Hypochlorite

This is a granular sanitizer that contains about 35% available chlorine. It dissolves quickly so it’s a great shock that leaves little build-up.

However, it’s usually more expensive than the others and of course, not as strong.

Trichlor FAQs

Dichlor vs. Trichlor: What’s the difference?

The main difference between Dichlor and Trichlor is the available chlorine. Trichlor has almost the highest available at around 90%, while Dichlor sits at about 55-62%.

Also, Trichlor will usually slightly lower a pool’s pH and total alkalinity, whereas Dichlor won’t because it has a more neutral pH balance.

What is a trichlor tablet?

A Trichlor tablet is a concentrated form of sanitizer that contains around 90% available chlorine and cyanuric acid for stabilizing it. It’s used for swimming pools and other water systems to kill germs.

Does trichlor lower pH?

Trichlor’s pH level is around 3, so it will slightly lower your pool’s level to match it. You’ll probably need a little pH increaser to keep it in a more neutral range.

Why is trichlor beneficial to daily chlorination?

Using trichlor to disinfect adds both sanitizer and stabilizer to your pool water. It’s also slow-dissolving, feeding your water the proper dosage as it’s needed.

Why is trichlor bad for pool shocking?

When shocking a pool, you are going for a quick, highly-chlorinated dose of sanitizer to kill off leftover contaminants or algae. Trichlor is designed to be slow-dissolving, making it ineffective for this purpose. 

Also, since they contain CYA, you risk getting too much of that product in your pool. 


The bottom line is that you can use any sanitizer you’d like and they’ll all do basically the same job. The difference is that some products are more effective or easier to use than others and Trichlor happens to fall in that category.

Whatever you decide, just make sure you’re testing your water and maintaining your pool on a consistent basis. This way, you’ll stay ahead of the game and keep yourself from working harder to reverse the effects of negligence!

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