Pool Chemicals

When correctly used in your pool, chlorine and other chemicals keep the water invitingly clear and sparkling clean. There are also risks and safety precautions to take when handling, using, and storing potentially hazardous pool care chemicals. In their stored, undiluted forms, they can be quite toxic. In fact, chlorine gas has been used as a chemical weapon since World War I. Knowing about proper use and storage of chlorines and acids can prevent an unexpected poisoning.


  • The two most commonly used forms of chlorine for home pools are calcium hypochlorite and trichloro-s-triazinertrione or TST. They are available as liquids, crystals, and in compressed tablets or sticks. Because they tend to break down when diluted and exposed to sunlight, “stabilizing” the pool water is necessary to slow the breakdown process and maintain adequate pool chlorine levels to retard algae and bacterial growth. Maintaining the proper chlorine concentration keeps the pool water clean and clear and also requires keeping the water a fairly precise pH, minimizing the concentrations of certain metals, such as iron, and maintaining the proper “hardness” of the water.
  • Muriatic acid, or hydrochloric acid, is a very strong acid in the form sold for use in pools. It is used to help sanitize the pool water and provide the proper pH to slow the breakdown of chlorine in the pool. 
  • Sodium carbonate, also known as soda ash, is a very strong alkaline or base. It is also used to adjust the water pH to the proper range to maintain proper chlorine concentration.
  • Cyanuric acid, a strong acid, is used to “stabilize” the pool water and prevent chlorine breakdown.

Other chemicals may include chelators to decrease the water’s iron concentration, calcium chloride to change the water’s “hardness”, a variety of algaecides, and flocculents, which improve water clarity by causing tiny particles to clump together and be filtered out.

Safety Rules for Using Pool Chemicals

  1. ALWAYS store pool chemicals and pool test kits in their original tightly sealed containers, in a locked, dry area out of the reach of children.
  2. NEVER rush the process of opening your pool for the season--it could result in giving in to a temptation to combine or skip steps.  Be prepared to spend several days to complete the process, even longer if you are inexperienced at it.
  3. ALWAYS follow the directions included with pool sanitizing chemicals.  Most pool supply stores will gladly answer any questions you may have about procedures and safety. Material Safety Data Sheets (MSDS) should be available for each chemical at the location where they are purchased.  Ask for them (they are free), bring them home and keep them in an easily accessible place. 
  4. NEVER mix concentrated pool chemicals together! An explosion or production of toxic gases could occur.
  5. Never pour chemicals into containers, which are wet or have contained other chemicals.  Do not use unlabeled chemicals.  Always use separate, clean measuring utensils for each chemical
  6. NEVER add water to chemicals.  Do as you oughtta. Add chemicals to water!  Separately!
  7. WASH out containers when empty, then dispose of them according to label directions.
  8. ALWAYS wash your hands well with soap and water after handling any chemicals.
  9. WAIT until the chlorine level is at the level recommended by the product before swimming in your pool, especially after “shock-treating” the pool.
  10. NEVER check identity or potency of pool chemicals by sniffing them. This could result in serious irritation or burns to the breathing passages.

DO NOT attempt to clean up a spill without protective clothing; any significant spill should be reported to the local fire department immediately for clean up. Self-contained breathing apparatus should be worn if there is any risk of exposure to chlorine gas.


  • Skin Exposures – Remove contaminated clothing.  Wash skin well with soap and water.  Flush the area with copious amounts of water for 15 minutes.  For dry powder chemicals, first dust off as much of the powder as possible.  Call the Indiana Poison Center.
  • Eye Exposures – Flush eyes under running water for at least 15-20 minutes.  Using eye drops should be avoided.  Call the Indiana Poison Center.
  • Respiratory Exposures – Immediately evacuate the area, moving at right angles from the wind direction to escape fumes.  Move victims to fresh air.  Call the Indiana Poison Center.
  • Chemical Ingestion – Do NOT induce vomiting.  Dilute with water or milk.  Call the Indiana Poison Center immediately.

Indiana Poison Center experts are standing by 24 hours a day, 365 days a year to help with poison emergencies. To learn more about poison prevention and to receive a free home safety check list, a magnet and phone stickers, call the Indiana Poison Center at 1-800-222-1222

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