What Pool Chemicals Cannot Be Added at the Same Time

Pool chemicals should be added one at a time, whether you’re balancing the water, shocking the pool, or adding a specialty chemical. For most water balance changes, the pump needs to run for at least four hours before you can add another chemical or retest the water. What Pool Chemicals Cannot Be Added At the Same Time?

Most common swimming pool chemicals are incompatible with each other & shouldn’t be mixed or stored together. Mixing organic chlorinating agents for pools & spas like (trichloroisocyanuric acid) & inorganic chlorinating agents (sodium hypochlorite) can lead to adverse reactions & chlorine gas release.

Never let pool chemicals contact each other. A harmful chemical reaction could happen, even when outside of the pool. Chlorine mixed with any other chemical or foreign substance can emit toxic gases, erupt in flames, explode, or all of the above. Always store chemicals in properly sealed secure containers in an area that’s cool, dry, well-ventilated, and away from kids.

What Pool Chemicals Cannot Be Added At the Same Time

When it comes to maintaining a pool, understanding which chemicals can and cannot be added at the same time is crucial for ensuring the safety of swimmers and the effectiveness of water treatment. Mixing certain chemicals can result in hazardous reactions, such as toxic fumes or explosions, and may also lead to ineffective water treatment.

Some chemicals for your swimming pool are incompatible and should be stored separately from each other and never mixed together for any reason. Chemicals should be added one at a time and in series with others. Perhaps most important of all never add chlorine and muriatic acid or Dry Acid together, whether outside the pool or in it.

This creates a dangerous toxic gas that can have severe health consequences if inhaled. Don’t ever shock the pool immediately after adding acid to the water. Also, never add acid to the pool when chlorine levels are high, such as after you’ve shocked the pool. Wait at least 4 hours or more between applications.

  • Never mix different types of chlorine together. Mixing incompatible pool chemicals can cause a dangerous chemical fire, explosion, or release of toxic fumes. In fact, mixing any type of organic and inorganic chlorine compounds meaning a stabilized and unstabilized chlorine can cause a bad reaction.
  • Store stabilized organic chlorine (dichlor shock and trichlor tablets) separately from your unstabilized inorganic chlorine (cal-hypo shock and liquid chlorine), both during pool application and while in storage. When shocking the pool, never put chlorine into the skimmers, especially if you have an inline or offline chlorine tablet feeder.
  • If using a floating tablet dispenser, pour the shock far away from the floating dispenser, or just remove it from the pool until the shock has enough time to dissolve. Don’t pour the shock right next to or on top of the dispenser.
  • Never mix new chemicals and old chemical
  • Improper storage of pool chemicals can cause chemicals to react with each other. Storing oxidizers (such as calcium hypochlorite) alongside acids (such as muriatic acid) is particularly dangerous, as these two chemicals can react on contact to produce chlorine gas.
  • Always read the chemical label

By avoiding the simultaneous addition of these incompatible chemicals, pool owners can maintain a safe and properly treated swimming environment. It’s essential to always read and follow the manufacturer’s instructions for each chemical product used and to store them safely to prevent accidental mixing. Regular testing of pool water parameters can also help ensure that chemical treatments are applied effectively and safely. Here’s a comprehensive guide to the pool chemicals that should not be added simultaneously:

Adding a clarifier that contains aluminum sulfate alongside a sequestering agent  HEDP can also result in cloudy pool water. Other ways to ensure safe pool chemical use include avoiding adding chlorine shocks to pool water containing high concentrations of metals or enzyme-based products.

*Other precautions include avoiding concurrent use of hardness increasers such as calcium chloride along with alkalinity increasers that contain sodium bicarbonate which can make your pool water cloudy and cause scale to form on your pool surfaces and equipment.

Chlorine & Acid

Perhaps most important of all — NEVER add chlorine and muriatic acid or Dry Acid together, whether outside the pool or in it. This creates a dangerous toxic gas that can have severe health consequences if inhaled. Don’t ever shock the pool immediately after adding acid to the water. Also, never add acid to the pool when chlorine levels are high, such as after you’ve shocked the pool. Wait at least 4 hours or more between applications.

Mixing chlorine and acid is extremely dangerous and should be avoided at all costs. When chlorine, typically in the form of sodium hypochlorite or calcium hypochlorite, comes into contact with acid, such as muriatic acid (hydrochloric acid) or sulfuric acid, it can produce toxic chlorine gas.

Chlorine gas is highly irritating to the respiratory system and can cause coughing, chest tightness, difficulty breathing, and even chemical burns. Additionally, chlorine gas is heavier than air, which means it can linger close to the ground and pose a greater risk of exposure.

Inhaling chlorine gas can lead to severe respiratory problems, including pneumonia and pulmonary edema, which can be life-threatening. Mixing chlorine and acid can also result in an exothermic reaction, leading to the release of heat and potentially causing burns or fires. Therefore, it is essential to never mix chlorine and acid, and always follow proper safety protocols when handling pool chemicals. If accidental mixing occurs, evacuate the area immediately, ventilate the space, and seek medical attention if necessary.

What Should I Do If I Accidentally Mix Pool Chemicals

If you accidentally mix pool chemicals, it’s essential to respond quickly and carefully to minimize any potential hazards. Here’s what you should do:

  1. Evacuate the area: Immediately move away from the area where the chemical mixing occurred to avoid exposure to harmful fumes or reactions.
  2. Protect yourself: If you come into contact with the mixed chemicals, remove any contaminated clothing and rinse affected skin thoroughly with water. If inhalation occurs, move to an area with fresh air. The Ultimate Pool Chemical Guide | Zodiac New Zealand
  3. Call for help: Contact your local poison control center, emergency services, or a professional pool service provider for guidance on how to handle the situation safely.
  4. Provide information: Be prepared to provide information about the chemicals involved, the quantities mixed, and any symptoms experienced to assist emergency responders in providing appropriate assistance.
  5. Ventilate the area: Open windows and doors to allow fresh air to circulate and dissipate any fumes from the mixed chemicals.
  6. Do not attempt to neutralize: Avoid attempting to neutralize the mixed chemicals unless instructed to do so by a professional. Adding other chemicals could exacerbate the situation and create further hazards.
  7. Contain the spill: If possible, contain the spill by using absorbent materials such as sand, clay, or vermiculite to prevent it from spreading further.
  8. Clean up carefully: Wear appropriate protective gear, such as gloves and goggles, while cleaning up the spilled chemicals. Use non-metallic tools to scoop up the mixture and dispose of it according to local regulations.
  9. Flush affected areas: Rinse any contaminated surfaces with copious amounts of water to dilute the chemicals and reduce the risk of residual contamination.
  10. Dispose of contaminated items: Dispose of any contaminated materials, such as clothing or cleaning tools, properly according to local hazardous waste disposal guidelines.
  11. Seek medical attention if necessary: If anyone experiences symptoms such as difficulty breathing, nausea, or skin irritation after exposure to the mixed chemicals, seek medical attention immediately.
  12. Prevent further accidents: Take steps to prevent future accidents by carefully reading and following the instructions on chemical labels, storing chemicals properly, and avoiding mixing incompatible substances.
  13. Document the incident: Keep a record of the incident, including what chemicals were involved, how the mixing occurred, and any actions taken in response.
  14. Review and learn: Use the incident as an opportunity to review pool chemical safety protocols and educate yourself and others about the importance of handling chemicals with care.
  15. Consult a professional: If you’re unsure how to proceed or want to prevent similar incidents in the future, consider consulting with a professional pool service provider for guidance on safe chemical handling practices.

Can I Use Household Bleach Instead of Chlorine In My Pool

Using household bleach as a substitute for chlorine in your pool is not recommended due to several reasons. Firstly, household bleach typically contains additional additives, such as fragrances or thickeners, which can interfere with water chemistry and potentially harm pool equipment.

Secondly, the concentration of chlorine in household bleach varies, making it difficult to accurately measure and maintain proper chlorine levels in the pool. This inconsistency can lead to ineffective sanitation or overdosing, both of which can result in water quality issues or damage to pool surfaces. Additionally, household bleach may not be formulated to withstand prolonged exposure to sunlight and other pool conditions, leading to rapid chlorine degradation and reduced effectiveness.

Using pool-specific chlorine products ensures that you are using chemicals specifically designed for water sanitation, with consistent concentrations and stability under pool conditions. It’s essential to follow manufacturer recommendations and dosage instructions when adding chlorine to your pool to maintain a safe and healthy swimming environment.

How Long Does it Take for Pool Chemicals to Work?

How fast Pool Chemicals work is dependent on the size of the pool, the pumping rate of the filter system & how much chemical is needed.
Alkalinity takes 6-8 hrs. or a full turnover of the pool water
PH is 4-6 hours.
Shock Chlorine- at least 30 min.
Cyanuric Acid- one full turnover……………………………………… Read more

How Can I Safely Store Pool Chemicals

Safely storing pool chemicals is crucial to prevent accidents and ensure their effectiveness. Here are several steps you can take to store pool chemicals safely:

  1. Choose a suitable storage location: Select a cool, dry, and well-ventilated area away from direct sunlight, moisture, and sources of heat. Avoid storing chemicals in areas prone to flooding or extreme temperature fluctuations.
  2. Use dedicated storage containers: Store pool chemicals in their original, tightly-sealed containers to prevent leaks and spills. If transferring chemicals to a different container, ensure it is made of compatible materials and clearly labeled with the contents.

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        Never Mix Pool Chemical Together
  3. Keep out of reach of children and pets: Store pool chemicals in a secure location inaccessible to children and pets. Consider using locked cabinets or storage bins to prevent unauthorized access.
  4. Store chemicals separately: Keep different types of pool chemicals separated from each other to prevent accidental mixing, which can cause hazardous reactions. Follow manufacturer guidelines for proper segregation and storage requirements.
  5. Follow storage guidelines: Adhere to manufacturer recommendations regarding storage temperature, humidity levels, and shelf life for each pool chemical. Dispose of expired or deteriorated chemicals properly according to local regulations.
  6. Store away from flammable materials: Avoid storing pool chemicals near flammable substances or ignition sources to reduce the risk of fire or explosion.
  7. Handle with care: When handling pool chemicals, wear appropriate protective gear such as gloves, goggles, and a mask to prevent skin contact, inhalation, or eye irritation.
  8. Avoid overstocking: Only purchase and store the amount of pool chemicals needed for immediate use to minimize the risk of accidental spills or leaks due to overcrowded storage areas.
  9. Inspect containers regularly: Check pool chemical containers regularly for signs of damage, leaks, or deterioration. Replace damaged or compromised containers immediately to prevent accidents.
  10. Secure lids and closures: Ensure that lids and closures on chemical containers are tightly sealed to prevent evaporation, spills, or contamination.
  11. Keep emergency supplies nearby: Store a spill kit, first aid supplies, and emergency contact information near the pool chemical storage area for quick access in case of accidents or spills.
  12. Educate household members: Teach family members and other household occupants about the dangers of pool chemicals and the importance of safe storage and handling practices.
  13. Post safety information: Display safety guidelines and emergency contact information in the pool chemical storage area to remind users of proper procedures in case of accidents.
  14. Plan for emergencies: Develop an emergency response plan outlining steps to take in the event of a chemical spill, leak, or exposure. Ensure all household members are familiar with the plan and know how to respond appropriately.
  15. Seek professional advice: If you have any concerns or questions about storing pool chemicals safely, consult with a professional pool service provider or chemical manufacturer for guidance and recommendations tailored to your specific situation.


In conclusion, mixing chlorine and acid is an extremely hazardous practice that can result in the formation of toxic chlorine gas. This gas poses serious risks to respiratory health and can cause severe irritation, difficulty breathing, and other respiratory complications.

Additionally, the exothermic reaction between chlorine and acid can generate heat, potentially leading to burns or fires. It is imperative to never mix chlorine and acid under any circumstances. Adhering to proper safety protocols when handling pool chemicals, including storing them separately and following manufacturer guidelines, is essential to prevent accidents and ensure a safe environment.

In the event of accidental mixing, prompt evacuation, ventilation, and seeking medical assistance are crucial steps to mitigate risks and protect health and safety. Awareness of the dangers associated with mixing chlorine and acid is paramount in maintaining a safe pool maintenance routine.

Can I add Alkalinity, and Shock at the Same Time?

No, Never add chemicals at the same time, whether you’re balancing the H2O, shocking the pool, or adding a specialty chemical. For most H2O balance changes, the pump needs to run for at least 4 hrs, or long enough for the pump to turn over the pool before you can add …………………………………………………….. Read more

JimGalloway Author/Editor


Leslies-Pools-Incompadible Pool Chemicals


What pool chemicals do I need to maintain my pool?

  • The essential pool chemicals for maintenance include chlorine or bromine for sanitation, pH increaser and decreaser to balance acidity, alkalinity increaser to maintain proper alkalinity levels, shock treatment for oxidizing contaminants, and algaecide to prevent algae growth.

How often should I test my pool water?

  • It’s recommended to test your pool water at least once a week to ensure proper chemical balance. Additionally, test after heavy pool usage, heavy rainfalls, or if you notice any changes in water clarity or odor.

Can I mix different pool chemicals together?

  • In general, it’s not recommended to mix pool chemicals unless explicitly instructed by the manufacturer or a professional. Mixing chemicals can create hazardous reactions and potentially harm you or damage your pool equipment.

 How do I lower the chlorine levels in my pool?

  • To lower chlorine levels in your pool, you can dilute the water by adding fresh water or use a chlorine neutralizer product specifically designed for this purpose. Additionally, reducing the amount of chlorine added during regular maintenance can help lower levels over time.

 What should I do if my pool water turns green?

  • Green pool water is often a sign of algae growth. To treat green water, shock your pool with a high dose of chlorine or algaecide to kill the algae. Brush the pool walls and floor to loosen algae, and run the filtration system continuously until the water clears. It may also be necessary to adjust pH and alkalinity levels.

 How can I prevent chlorine odor in my pool?

  • Chlorine odor in pools is typically caused by chloramines, which form when chlorine combines with organic contaminants. To prevent chlorine odor, maintain proper chlorine levels, regularly shock the pool to oxidize contaminants, and ensure adequate filtration and circulation. Additionally, encourage swimmers to shower before entering the pool to reduce the introduction of organic matter.

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