Bad Pool Chemical Combinations

Written by Michael Dean
February 7, 2024

maintaining a swimming pool with a hazard sign next to them

Any swimming pool owner knows your chemicals are super important in pool maintenance. However, the same chemicals beneficial to your pool can be dangerous if mishandled. For example, some bad pool chemical combinations can be hazardous for your pool. 

In this article, I’ll discuss bad chemical combinations to avoid at all costs, best practices for pool chemical handling, and more.


Main Takeaways

  • Bad chemical combinations to watch out for include chlorine + ammonia, chlorine + acids, chlorine + bromine, and much more!
  • Adding pool products in the right order is crucial to prevent any hazardous chemical reactions.
  • Chemicals combined in the wrong order can also lead to skin and eye irritation and even severe respiratory distress.

Bad Pool Chemical Combinations to Watch Out For

When it comes to pool maintenance, several chemical combinations must be avoided since mixing some can be quite dangerous. Here’s a list of chemical combinations to avoid.

Chlorine + Acids

Combining certain types of acid, such as muriatic acid, or a pH reducer, such as sodium bisulfate, with chlorine will release chlorine gas. This is a dangerous substance when inhaled and can cause severe harm to your lungs and a compromised respiratory system. Always wait a few hours before adding one after the other to the swimming pool.

Chlorine + Bromine

Never EVER mix two kinds of pool sanitizers, including chlorine and bromine. Mixing chlorine and bromine, whether in dry form or in the water, can lead to a very nasty chemical reaction. When switching from one sanitizer to the other, always make sure there is no more trace of the previous chemical.

Pool Shock + Algaecide

While not directly harmful, mixing pool shock with certain types of algaecide could result in harmful byproducts that reduce the efficiency of both chemicals. You should wait at least 24 hours after chlorine shock (waiting for the chlorine levels to return to normal) before adding algaecide.

Trichlor/Dichlor + Cyanuric Acid (Stabilizer)

Cyanuric acid (or CYA) is commonly used in outdoor pools to stabilize chlorine levels and protect the chlorine from the sun’s harmful UV rays. If you use trichlor or dichlor to sanitize your pool, there is absolutely NO NEED to add CYA, as trichlor and dichlor are already stabilized (i.e., already contain CYA). If you’re dealing with too much stabilizer, check out my article on lowering cyanuric acid levels.

Pool Shock + Metals

Before you shock the pool, make sure you test the level of metals in the water. If you shock the pool with too many metals in the water, it may oxidize and cause staining on your pool surfaces. These stains can be a major pain to deal with, but if you catch them early, you’ll generally only need a bit of ascorbic acid to clear them up.

Pool Shock + Metal Sequestrants

Unfortunately, chlorine shock can lessen the effectiveness of certain chemicals, such as metal sequestrants. Sequestrants bind metals, but chlorine shock breaks these bonds. This releases the metals back into the water, which can cause staining and other issues. Always wait 24 hours before adding the chlorine shock after adding the sequestrants to allow the chemical to circulate around the pool.

Calcium Hardness Increaser + pH/Alkalinity Increaser

If you raise your calcium hardness level right after raising your pH or alkalinity with a pH or alkalinity increaser, it can lead to cloudy water. Furthermore, this can lead to unsightly scale buildup on your pool surfaces.

Chlorine Shock + Enzymes

The chlorine in the pool shock can disrupt the enzymes, preventing them from doing their job. Just like algaecide and metal sequestrants, always wait for the chlorine levels to drop back down to normal before adding this chemical – otherwise, you’re just wasting money.

Best Practices for Safely Using and Storing Pool Chemicals

Safety is crucial when handling pool chemicals. Keep reading to learn the best practices and my top tips for using and storing pool chemicals.

Keep Them Separate

Wet or dry, chemicals need to be kept separate at all times—if not, a fire hazard or explosion may occur due to close proximity of dangerous substances. Avoid stacking chemicals on top of each other, and never mix them in the same container!

Keep Them Sealed

You should thoroughly seal your pool chemicals after using them. This is absolutely crucial for your safety. When unpacking or storing chemicals, make sure the lids are tightly capped or screwed on.

Label Your Chemicals

Just to be on the safe side, label your pool chemicals (if you’re not keeping them in the original container) with a marker with the following information: name, type, weight, warnings, and expiration. This will help you and any others who might need to use them for the pool (for instance, if you’re away on vacation and someone who is housesitting for you has to top up the chlorine levels).

Store Them Safely

Exposing chemicals to air or heat for long periods is a bad idea. Store them in a cool, dry, well-ventilated, and secure area. Make sure to keep the chemicals away from any moisture or direct sunlight.

Read Package Labeling

Always read the information on the product’s label carefully. It often includes useful information on handling, storing, and disposing of the chemicals.

Wear Protective Gear

Protective gear, such as gloves, goggles, and a mask, is absolutely crucial when you’re handling and mixing chemicals. Proper PPE gear will help guard your skin, eyes, and lungs from possible exposure.

Use Dry Measuring Tools

When handling chemicals, use clean, dry measuring tools (scoops and cups) to prevent possible cross-contamination and to ensure accurate measurements.

Add Chemicals to Water, Not Water to Chemicals

When mixing, NEVER pour water onto the chemicals. It is always best to pre-dissolve the chemical into the water first. This prevents the chemicals from splashing on your skin or into your eyes. Always add the substance slowly and stir the water to allow the chemical to dissolve.

Wash Your Hands!

Once you’re done handling the chemicals, always rinse your hands thoroughly with a rich lather of soap and water to remove any lingering chemical residue.

Dispose Chemicals Safely

When you have to dispose of any unused, excess, or expired pool chemicals, please do so according to local regulations in your county. Do NOT pour chemicals down the drain or into water bodies. Talk to an expert if you’re unsure how to proceed with safe disposal. Check my guides on disposing of chlorine and muriatic acid for more info!

Is There an Order to Adding Pool Chemicals to Your Pool? 

Yes, there is! You can’t add chemicals all at once or in any order you like. Here’s a quick look at the order in which you must add chemicals to your pool.

1. Alkalinity Adjuster

Alkalinity lays the foundation for your pool—it has a significant influence on the pH balance of your pool. Your alkalinity should be at 80 to 120 ppm.

2. PH Adjuster

pH is what measures how acidic or basic your water is. It indicates your pool’s health and is measured on a scale from 0 to 14, with 7 being neutral. For your pool, the pH of the water should ideally be kept in the range between 7.2 to 7.6—not too acidic and not too alkaline.

3. Calcium Hardness

Once alkalinity and pH have been adjusted, you can focus on adjusting calcium hardness. Calcium is fairly stable once added, more so than pH and chlorine, and ideal calcium levels for a pool should hover between 200 and 275 ppm for a concrete or plaster pool and 175 to 225 ppm for a fiberglass or vinyl pool.

4. Chlorine

Finally, it’s time to sanitize your pool! Chlorine is one of the most widely available forms of pool sanitizer. It oxidizes contaminants such as bacteria, algae, oils, dirt, and other unwelcome visitors. Chlorine levels should be between 1 and 3 ppm. Too much chlorine can irritate swimmers, and too little chlorine will not properly sanitize your water. 

5. Cyanuric Acid

Cyanuric acid stabilizes the levels of chlorine in the pool, which helps it last longer in the pool even under the threat of the sun’s UV rays. You must add CYA separately if you are using an unstabilized chlorine. CYA levels should typically be around 30 to 50 ppm.

6. Algaecide

Algaecide is a preventive measure against algae, which can take root following rain, on hot days, or after a pool party. The last thing you want to deal with is an algae infestation, so make sure to add algaecide to protect your pool.

7. Salt (for Saltwater Pools)

Finally, if you have a saltwater pool, you must add salt. Make sure you are adding proper pool salt, which is 99% pure sodium chloride, not your average kitchen or table salt. The recommended levels for a saltwater pool range between 2,700 and 3,400 ppm.

Need Some Maintenance Help?

Send me a message! I can answer any of your pool maintenance, equipment, or other questions.

Be Safe When Adding Pool Chemicals

Keeping your pool’s chemical balance balanced at all times is essential for a safe and enjoyable swimming experience. The more familiar you become with how to handle chemicals, the easier it will be to keep everything in check. And remember, when in doubt, call a professional! Pool chemicals can be dangerous if mishandled, so it’s better to be safe than sorry!

Do you have any more questions about pool chemicals and pool maintenance? Get in touch!

Scroll to Top