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All About the Chlorine Demand

What is a Chlorine Demand?

A chlorine demand is when Total Chlorine (the dead stuff that has already sanitized the pool) outnumbers Free Chlorine (the good stuff that is actively sanitizing the pool).

Chlorine Demands can be caused by:

  • Bacteria
  • Bather Waste (Sweat, Urine, Suntan lotions, Hair products)
  • Organics (Dirt, Leaves, Pollen, Rain, Wind)
  • Fertilizers containing nitrates & phosphates
  • Pollution
  • Keeping solar & auto covers on for extended periods of time

Recently featured on ABC 7 and Accuweather.com:

How do you identify a chlorine demand?

  • If the pool doesn’t hold chlorine after repeated shocking.
  • After adding shock you notice a white blooming cloud form and dissipate.

How do you treat a chlorine demand?

Bring a water sample to a Caribbean Pools retail location and have your water tested for Chlorine Demand. Caribbean Pools uses Alex Pro by BioGuard. Alex will recommend the proper dosage of chemicals in order to break the chlorine demand.

Once we’ve confirmed you have a chlorine demand, try to eliminate the cause of demand. Choose your strategy; There are two ways to treat demands (sometimes a combination is necessary)

  • Perform multiple drain and re-fills to dilute the demand water with fresh water.
  • Add a large amount of shock in order to make Total Chlorine and Free Chlorine match. In some instances, multiple large shocks may be necessary. 

How do you prevent a chlorine demand?

  1. Try to keep contaminants to a minimum
  2. Stick to a weekly maintenance schedule which helps keep Total Chlorine and Free Chlorine balanced
  3. Have your water analyzed at least twice a month to maintain proper water balance

Remember, some chlorine demands are unavoidable! We can’t control what Mother Nature puts into our pool!

If you have a chlorine demand with algae. Here are some additional instructions:

pool faq chlorine demand




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