What Is Chlorine Shock?
Chlorine is a commonly used pool sanitizer. It sanitizes by killing algae, bacteria, and other pathogens and binding with unwanted substances such as skin cells, oil, urea, leaf litter and other debris to form chloramines or combined chlorine compounds. These can cause eye irritation and an unpleasant “chlorine-like” odor. This process of sanitation together with normal degradation caused by sunlight reduces the levels of freely available chlorine in the pool.
Pool shock chlorine
A chlorine pool shock works to increase the levels of free chlorine back to safe levels. Shocking a pool is effectively adding a super dose of chlorine to bring the pool to a chemical point known as breakpoint chlorination where there is enough chlorine in the water to eliminate the bonds that are combining chlorine to contaminants. This process is best visualized by referring to the graph on our breakpoint chlorination page. Chlorine shock is compatible with chlorine, bromine and ozone sanitizing systems.
There are a wide range of chlorine based pool shock treatments on the market. The active ingredients typically used are: Calcium Hypochlorite, Dichlor, Sodium Dichor, or Lithium hypochlorite (also known as Lithium Shock). See more on the different types of chlorine in our article on pool chemicals. The key criteria to consider when comparing different products is the level of available chlorine. Most of the top brands offer shock treatments with 45-75% available chlorine. 65% is recommended by most pool experts with 75% treatments – often referred to as “super shock” or “shock plus” – useful for messy Spring start ups or to rid the pool of stubborn algae blooms. If a chlorine shock is advertised as a blended product, perhaps with water balances, flocculants or clarifies, it’s always a good idea to check for available chlorine levels.
Both liquid and granular chlorine shock treatments are available and you’ll find more information on our liquid pool shock page. Liquid shock tends to be more expensive when available chlorine levels are taken into account but has the benefit of eliminating the potential for damage to pool surfaces. But you can normally avoid bleaching risk by choosing a quick dissolving granular product as this minimizes contact time with the liner and other surfaces. Look our for chlorine shock treatment products that are made with super fine chlorine granules.