What is shock and why should you shock your pool? Shock is super chlorinating the water to dissolve any chloramines, bacteria, or and other organic compounds that can cause skin irritation, unpleasant water smell, and cloudy water. This can also include algae build-up as well as oils and sweat. Chloramines build up whenever the pool is used and sanitizing using normal chlorine levels will not rid your water of them. Have you ever been around a hotel pool or indoor pool and it smelled very strongly of chlorine? That’s chloramine creating that smell, not chlorine. This very clearly shows that the water chemistry in that pool is not balanced correctly and can be unhealthy.
Understanding When to Shock Your Pool
The most important tests for knowing when to shock are free chlorine, combined chlorine, total chlorine, and breakpoint chlorine. Free chlorine is the amount of chlorine in the water that is active and available to sanitize the water and ideally you want this to be between 1-3 ppm. Combined chlorine is chlorine that are chlorine molecules that has already been used and have attached themselves to organic compounds, turning into chloramine and this should be less than 0.2 ppm, as the more this rises, the more chloramines are in the water, causing issues for you and anyone who swims in your pool. Total chlorine is the equation that subtracts combined chlorine from free chlorine. Breakpoint chlorine is the amount of chlorine needed to break the molecular bonds of the chloramine atoms in the water. It is recommended to put 10 times the amount of chlorine into the water as the total chlorine calculation. For example, if free chlorine is 3ppm and combined chlorine is 0.5ppm, you would have a total chlorine calculation of 2.5ppm, and therefore you would want to make sure you get the water to 25ppm of chlorine to reach breakpoint which will start fresh with your ability to keep clean and safe water.
Types of Pool Shock
The types of shock are the following 3 common offerings.
Calcium Hypochlorite (Cal-Hypo)
Calcium hypochlorite is a very effective sanitizer that has been used for nearly 100 years to keep pool water clean and clear. In professional strength applications the chlorine availability is between 65% - 75%. It is recommended to use it after the sun has gone down as it has no UV protection and the sun will deteriorate it as quickly as you can get it into the water. You will need to wait atleast 8 hours to swim after application and never put it in through your skimmer. It is highly recommended to mix it in a bucket of water separately then walk it around the pool as you pour it in. Calcium hypochlorite can react negatively when in direct contact with dichlor and/or trichlor, so if you have a tablet feeder in your system or a tab floater in the pool, make sure they are empty before using a calcium hypochlorite shock. As it says in the name, calcium hypochlorite is made of calcium and will add that to your water when using it, so please make sure you are aware of that when choosing Cal-Hypo as your choice of shock.
Dichlor or Trichlor Shock
Dichlor or trichlor shock combines chlorine and cyanuric acid (which is also known as stabilizer) in dichlor and adds muriatic acid in trichlor to help stabilize pH. Dichlor and trichlor contain between 50% - 60% chlorine and should never be allowed to get wet before going into the pool water. It can release extremely toxic fumes if the granular or tablets get wet. Dichlor and trichlor can be added directly to the water and most tablets used in swimming pools are trichlor.
Non-Chlorine Shock
Non-chlorine shock is a way to shock the pool and be able to swim almost immediately. It is typically made up of potassium peroxymonosulfate and is the recommended shock for salt water pools. Although it is labeled as a shock for pools, it is not an algaecide and will not kill algae.
Important Precautions and How to Shock Your Pool
Shocking your pool is fairly straightforward, but you should take some precautions before purchasing, storing, and using these chemicals. Remember, you are trying to super chlorinate the water and accomplishing that will require heavy duty chemicals. Please make sure you have a dry and dark place to store the chemicals, as any water or moisture into the shock can cause it to deteriorate in the best case and to cause extremely toxic fumes in a bad case scenario.
Before shocking the water, make sure your filter is clean and all your baskets are empty. Once shock is applied you should run your pump for 24 hours, and if you have a variable speed pump then a higher speed is recommended to help disperse the shock and make sure all chloramines and other organic matters are destroyed.
