Can You Mix Chlorine Types?

Written by Michael Dean
February 7, 2024

mixing chlorine types

If you only have a couple of scoops of pool shock left, you may wonder if you can just mix it with another type of chlorine to get the proper dosage. After all, both products are technically chlorine, so how much harm could they do when mixed? Trust me. I’ve been there. But mixing different types of chlorine is a ticking time bomb that can be a recipe for disaster.

In the article, I will discuss whether or not you can mix different types of chlorine and walk you through how to store chlorine safely and securely. Let’s get started!

Main Takeaways

  • Mixing different types of chlorine compounds is never a good idea because it can cause dangerous chemical reactions such as explosions or toxic fumes.
  • You should always store chlorine in a shaded, dry, and well-ventilated area.
  • It is safe to shock your pool with cal hypo while using trichlor tablets for your standard chlorine treatment, but be very careful to ensure the undiluted chemicals do not come into contact with each other.

Can You Mix Different Types Of Chlorine?

You should NEVER mix different types of chlorine. Mixing these chemicals can cause a whole host of problems and should always be avoided. Even though these chemicals may look the same and serve the same purpose in your pool, it is unsafe to mix them.

Types of Chlorine Used in a Pool

It’s an easy mistake to think that all types of chlorine are the same. In reality, chlorine is a broad term encompassing various chemical substances that contain a chlorine molecule. Examples of the different types of chlorine are:

Calcium Hypochlorite

Calcium hypochlorite or cal hypo is a fast-dissolving granular form of chlorine that contains calcium hypochlorite as the main active ingredient. It does not contain cyanuric acid, so it is not resistant to sunlight. Cal hypo has a high chlorine content of 65-75%, which is why it is most commonly used for shock treatments.

Sodium Hypochlorite

Sodium hypochlorite, also known as liquid bleach, is a liquid form of chlorine. This means sodium hypochlorite doesn’t need to be pre-dissolved in water and can be added directly to the pool water.

Like cal hypo, sodium hypochlorite is unstabilized, so you’ll need to use it with a stabilizer to prevent it from breaking down rapidly in the sun. And it is important to note that of all the types of chlorine, sodium hypochlorite is the least potent, with only around 10% chlorine content.

Lithium Hypochlorite

Lithium hypochlorite is a granular form of chlorine that is quick-dissolving and unstabilized. This type has a reasonably high chlorine content of around 30% and is pH-neutral. Lithium hypochlorite is less common than the other types of chlorine I’ve mentioned here because it is much more expensive.


Dichlor is a powerful form of chlorine with a concentration of around 60% that comes in either granular or tablet form. It contains chlorine and cyanuric acid, typically used for regular pool maintenance rather than shocking. However, with that said, dichlor can still be used to shock the pool.


Trichlor is the strongest type of chlorine, with 90% potency. This type of chlorine is only found in tablet form and dissolves very slowly in pool water. If you are looking for a type of chlorine that will keep your chlorine levels topped up for an extended period of time, trichlor is a good option. However, one downside of trichlor is that it has a low pH, so it may affect the pH balance of your pool.

If you’re looking for more info on these types of chlorine, check out my article on the different types of chlorine.

What Happens When You Mix Different Types of Chlorine?

As I mentioned above, mixing different types of chlorine is a fast track to a pitfall. When mishandled, these products can become dangerous and unstable, resulting in explosions, fires, or exposure to toxic gases, which are extremely dangerous for your health.

But why does this happen? Chlorine is an oxidizer that is very efficient at breaking down substances, which is why it is used in pools. But when two chlorine products come into contact with each other, a violent chemical reaction can occur, causing them to destabilize and… well… kaboom!

Dichlor and Trichlor

Dichlor is a particularly sensitive form of chlorine that should be stored safely. When dichlor and trichlor are mixed, they can release toxic gases such as chloramine or nitrogen trichloride, both of which may cause respiratory problems and skin or eye irritation.

Dichlor/Trichlor and Cal Hypo

Mixing dichlor or trichlor (both of which contain cyanuric acid) with cal hypo (which doesn’t contain cyanuric acid and is highly alkaline) results in a rapid release of chlorine gas. Chlorine gas is extremely toxic and can cause severe respiratory distress. At high enough levels, breathing chlorine gas can result in coughing up blood, serious lung damage, and even death. This rapid release of chlorine gas can also lead to a fire or an explosion.

Dichlor/Trichlor and Sodium Hypochlorite

Mixing dichlor or trichlor with sodium hypochlorite (liquid bleach) produces a similar chemical that releases toxic chloramine gas. Chloramine gas can damage the respiratory system and cause breathing difficulties, leading to pulmonary irritation and pneumonitis.

Cal Hypo and Sodium Hypochlorite

Mixing cal hypo and sodium hypochlorite also results in a release of chlorine gas when mixed, which, as you know by now, is a hazardous substance that can easily result in an emergency trip to the hospital.

Safety Tips When Using Chlorine

Chlorine is not the most volatile substance in the world, but it must be handled with care to avoid damage to your pool equipment or yourself. Here are some of the most important safety tips to follow when handling chlorine.

Read and Follow the Instructions

Make it a habit to always read the information on a product’s labeling and packaging. I know this may seem redundant, but the instructions provided by the manufacturer are your key to safety. Note the recommended dosage, application methods, and safety precautions.

Always Wear Proper PPE

PPE is a non-negotiable when handling chlorine. Wearing safety gear, such as gloves, goggles, and a mask, helps protect your skin, eyes, and respiratory system from potential exposure to chlorine and its fumes. You should also make sure no skin is exposed, so wear long sleeves, pants, and closed-toe shoes.

Ventilate the Area

Does the area you’re working in or storing your chemicals have good airflow? Proper ventilation in the pool area minimizes the buildup of any hazardous fumes. Use fans, open windows, or work in outdoor areas whenever possible to allow for good air circulation. Never work with chlorine in tight, enclosed spaces.

Handle With Care

When handling chlorine products, be careful and avoid contact with your skin or eyes. This might sound obvious, but you won’t believe how easy it is to forget this when you just need to scratch that itch in your eye.

Store Properly After Use

Store chlorine products in a cool, dry area away from flammable materials, direct sunlight, and any sources of heat or dampness—as well as each other!

How to Safely Store Chlorine

If you fail to store your chlorine products correctly, you risk them destabilizing, spilling over, or reacting with each other. Here are my top tips for storing chlorine.

Choose a Suitable Storage Location

You should always store chlorine in a cool, shaded, well-ventilated area. This area should be secure, away from direct sunlight, heat sources, flammable materials, combustible substances, acids, and other incompatible chemicals.

Use Proper Containers

Always store chlorine in its original, tightly sealed container to prevent spills and leaks. If you’re transferring chlorine to another container, ensure it is specifically designed for chemical storage, is compatible with chlorine, and does not contain traces of other chemicals.

Label Containers

Get out your black Sharpie and clearly label all containers with the name of the chemical, hazard warnings, and storage instructions. This is especially vital if you have discarded the original packing since it helps to identify the contents and how to handle them.

Exception: Shocking With Cal Hypo When Using Trichlor Tablets

An exception to the rule of mixing the different types of chlorine is combining cal hypo shock with trichlor tablets. While direct mixing is still an absolute no-no, using both in the same pool is possible, especially if you’re looking to treat a serious algae infestation. However, you need to be careful not to allow the solid chemicals to come into contact with each other—never place cal-hypo in a chlorinator where there might be trichlor tablet residue, for instance.

In my opinion, the best approach when shocking your pool is to pre-dissolve the cal-hypo in a bucket and then pour that slowly in front of a return jet while the pump is running, and after an hour or so of circulation, add the trichlor tablets. That way, there is no possibility of contact with the solid chemicals.

Get My Free Pool Care Checklist

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Bottom Line

Developing a healthy respect for pool chemicals is the first step toward handling them safely and avoiding disaster! Doing so is essential for a safe and clean pool environment, as is understanding the different types of chlorine, their properties, and potential reactions when mixed.

Still have some doubts about the chlorine in your pool? Feel free to reach out! I am here to help.

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