Quick Definition:

Superclorinating (shocking) a pool is the process of adding shock material into the pool water to meet or exceed chlorine demand, resulting in clearer pool water.

What is Superchlorinating (shocking)?

Superchlorinating, also called shocking, is the process of raising and maintaining the level of an oxidizer in the water to eliminate harmful contaminates, and to remove impurities from the water.  Shocking the pool not only eliminates microorganisms and organic and inorganic contaminates from the pool, the pool water will look much clearer and vivid, an indicator the shock treatment did its job correctly.

For chlorine-based shock products, a chlorine level of 10 ppm is recommended.  This chlorine level far surpasses the chlorine demand, overwhelming the microorganisms and completely oxidizing them.

There are also non-chlorine based shock products available, such as Potassium Peroxymonosulfate.  Non-chlorine shocks are more expensive, but the chlorine level is not increased, allowing for a fast turnaround time between shocking and ability of the water to be safe for swimming.

The basic steps for superchlorinating a swimming pool are to:

  1. First determine how much combined chlorine there is in the pool.
  2. Add the chlorine amount appropriate for the pool size and combined chlorine.
  3. When using chlorinated shock, this should be done in the evening when there is little sunlight to avoid chlorine neutralization from the ultraviolet (UV) radiation. The pool should sit open and uncovered overnight, or about 8 hours.
  4. The swimming pool water should be tested for all water balance tests; alkalinity, pH, and calcium hardness, plus the level of sanitizer, such as chlorine or bromine, should be measured.
  5. Any water imbalance found from testing should be corrected at this time, then tested again within 24 hours.


  • “Pool & Spa Water Chemistry, A Testing and Treatment Guide, Waterproof Edition, 2005. Taylor”

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