Chemical Tips
NEVER mix chemicals. This can cause an explosion and or fire. Chemicals should never be mixed together before adding them to your pool water. Not mixing doesn’t just mean not physically mixing them together. It also means having separate measuring cups for each chemical. Using one measuring cup is inviting a mixing disaster. NEVER pour them all in at once either. Combining pool chemicals can cause dangerous reactions/explosions, fire and even reduce their effectiveness. Generally speaking, almost all pool chemicals are incompatible in some ways. Safe handling and the proper application is the key!
Common Mistakes
- More is always better – Not true. Using too much chlorine or shock can mess with your pool’s chemical balance and cause damage to your pool liner (above ground pool) and or walls (fiberglass or gunite). Understanding the pool chemistry basics is key to keeping your water clean and clear which ultimately keeps it safe to swim in.
- pH & Alkalinity – These chemicals work together to maintain water balance. If your pH is too low then the water becomes acidic. If your pH is too high then your water gets cloudy. Your pH should be between 7.2 and 7.8. It’s best to bring your water sample in to be tested 2 times a week.
- Stabilizer – Keeping a stabilizer (cyanuric acid) in your pool helps keep the chlorine in the pool. Maintaining the correct level can help your chlorine work smarter, not harder. Without it the chlorine burns off too quickly in the sun.
- Product Label – You should always read and follow the product label on each product. The label will include warnings, safe handling, safe storage, and proper application instructions. If it is missing the label don’t use it until you contact the manufacturer of the product for a guide sheet.
- Storing Chemicals Improperly – Pool chemicals can be volatile. They should be stored in a cool, dry, well-ventilated place. Avoid direct sunlight and moisture. Both can turn your chemicals deadly. Keep liquid chemicals away from dry chemicals. Don’t stack them on top of each other. Always keep the chemicals in the containers they come in. Make sure you store the chemicals with lids tightly attached and out of reach of children and animals. 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.
- Safety Measures – Using lax safety measures can cause injury. Part of respecting pool chemicals is taking the necessary safety precautions to prevent injuries. But mistakes happen. When they do, you’ll be glad you’re wearing rubber gloves and goggles to protect yourself. Other safety measures that need to be enforced included locking up your pool chemicals so kids and animals can’t get to them.
- Ignoring instructions – Pool chemicals are labeled with explicit instructions from the manufacturer. The CDC says to follow them to the letter. In general, most pool chemicals should be applied directly to the pool water, not mixed with water first. NEVER apply chemicals when people are in the water.
A list of incompatible pool chemical combinations
They definitely should NEVER be mixed together
Chlorine & Acid
Most important – NEVER add chlorine and muriatic acid or dry acid together. Not in the pool and Not outside the pool. NEVER! This creates a dangerous toxic gas that can have severe health consequences when inhaled. Don’t ever shock the pool immediately after adding acid to the water. Never add acid to the pool when your chlorine levels are high, so don’t add acid after you shock your pool. 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. Wait a minimum of at least 4 hours or more between applications.
Stabilized & Unstabilized Chlorine
NEVER mix the different types of chlorine together. These chemicals are incompatible and will cause dangerous chemical fires, explosion, or a release of very toxic fumes. Mixing any type of organic and inorganic chlorine compounds like stabilized and unstabilized chlorine can cause an adverse reaction. Stabilized chlorines are dichlor shock and trichlor tablets. Unstabilized inorganic chlorine are cal-hypo shock and liquid chlorine. Keep your stabilized organic chlorine separate from your unstabilized inorganic chlorine both during pool application and while in storage. Do NOT store together!
Calcium Hardness Increaser & Alkalinity Increaser
When you add a hardness increaser and sodium carbonate or sodium bicarbonate to close together will cause a reaction, creating calcium carbonate. It’s a very bad idea. These two chemicals are incompatible. They will cause cloudy water and increased scaling on the pool surface and equipment. These chemicals should be added on separate days from each other. Add harness increaser on a different day than alkalinity increaser or soda ash to avoid this issue.
Water Clarifier & Chelating or Sequestering Agents
Do not add clarifier on the same day as a chelating or sequestering agent. Chelating and sequestering agents are Stain & Scale Removal, Stain & Scale Prevention, Metal Out, etc. If you are in the middle of a stain removal process do NOT use clarifier. This will cause your water to cloud up quickly and this problem cannot be cleared with filtration.
Chlorine Shock & Algaecides
These two chemicals are very crucial to addressing an algae bloom in your pool. They should NEVER be used together or even at the same time. When dealing with algae you will want to start by shocking the pool water to kill the algae which brings the issue under control. Once the chlorine levels have decreased then you can go ahead and add the algaecide to boost the pools ability to fight against the algae. In all cases you should always refer to the each product label’s instructions. Different types of algaecide treatments may require a different set of application steps.
Pool Shock w/Metals in the Pool
Before you treat your pool you should always get your water tested and follow the treatment plan. When you add shock to your pool water that has metals in the water it can cause oxidation staining to appear on the pool surface. It may also trigger issues with colored pool water. NTXPool Water Testing Station will test for metals in the pool.
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.
Enzyme Products & Pool Shock
If you are using enzyme products avoid adding pool shock immediately before or after the enzymes. These two chemicals are incompatible. Shock will destroy the enzymes you just put in your pool water. Wait for your chlorine levels in your pool to have drop below 4.0-5.0 before adding enzymes. As always refer to the product label recommendation for both chemicals.
Chlorine & Bromie
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.
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.
Most common swimming pool chemicals are incompatible with each other and should never be mixed. Mixing of organic chlorinating agents (such as trichloroisocyanuric acid) and inorganic chlorinating agents (such as sodium hypochlorite) can lead to fires, explosions and chlorine gas release. Adding sodium hypochlorite to pool water containing muriatic acid, a chemical used to lower total alkalinity, can also produce chlorine gas.
Taking precautions to avoid improper mixing of incompatible pool chemicals is important to prevent accidents. These precautions include avoiding concurrent use of hardness increasers (such as calcium chloride) and alkalinity increasers (such as sodium bicarbonate), which can make your pool water cloudy and cause scale to form on your pool surfaces and equipment.
Adding a clarifier (such as aluminum sulfate) alongside a sequestering agent (such as hydroxyethylidene diphosphonic acid) can also result in cloudy pool water. Other ways to ensure safe pool chemical use include avoiding adding shocks to pool water containing high concentrations of metals or enzyme-based products.
MAIN TAKEAWAYS…
New and Old Chemicals should never be mixed together. If you have a little bit of an older chemical left over, do not pour it into the same container as your new chemical. Even if its the same chemical do not mix them. Finish using the old chemical while it’s still good and then use your new chemicals.
Most importantly remember that most pool chemicals are inherently incompatible with one another. Do NOT mix chemicals. If there is a question as to when products can be added, always carefully read and follow the directions on the product label, seek advice from a professional or call the product manufacturer. Product label instructions will also provide other warnings, including maximum pool dosage per day, safe application and handling instructions, as well as storage recommendations. When in doubt, waiting at least 4 hours between chemical applications is never a bad idea.
Safe storage of pool chemicals can be achieved through separating incompatible chemicals using storage cabinets, secondary containment or distance. Only like chemicals should be stored near to each other. When storing chemicals, always choose a cool, dry and well-ventilated area out of direct sunlight and away from sources of moisture. It’s also important to avoid storing liquid chemicals above dry chemicals. If spilled, liquid chemicals may leak into other containers and onto the floor. Protecting against pool chemical hazards doesn’t have to be a challenge. By taking steps to avoid improper mixing or storage of incompatible pool chemicals, you can help prevent accidents and pool chemical injuries.
- 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.
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).
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.
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 add pool chemicals to your pool?
Yes, there is!
1. Alkalinity – Alkalinity lays the foundation for your pool—it has a significant influence on the pH balance of your pool.
Alkalinity should be at 80 to 120 ppm.
2. pH – 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.
pH range between 7.2 to 7.6—not too acidic and not too alkaline (cloudy).
3. Calcium Harness – After the alkalinity and pH have been adjusted, then you can focus on adjusting calcium hardness. Calcium is fairly stable once added.
200 and 275 ppm for a concrete or plaster pool
175 to 225 ppm for a fiberglass or vinyl pool.
4. Chlorine – 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. Remember to much chlorine can irritate swimmers, and too little chlorine will not properly sanitize your water…balance is the key.
Chlorine levels should be between 1 and 3 ppm.
5. Cyanuric Acid – Cyanuric acid stabilizes the levels of chlorine in the pool, which helps it last longer in the pool. 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, if foliage falls into the pool, high algae environment, and or after a pool party. You don’t want to deal with an algae infestation, so make sure to add algaecide to protect your pool. Follow the instructions on the product label.
7. Salt (for Saltwater Pools) – 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.
Recommended levels range between 2,700 and 3,400 ppm.