Pool owners know that the list of pool chemicals needed to maintain a sparkling clear swimming pool is long. Whether you have a saltwater pool or a traditional chlorine pool, one of the most important chemicals on that list is pool shock. Here, we will discuss when, why, and how to shock your pool so that your pool water is healthy and balanced for the entire swim season.

Reasons to Shock Your Pool

Giving your pool a regular shock treatment quickly raises the amount of chlorine in your pool. It is important to do this for many reasons. First, pool shock kills bacteria and algae that regular sanitizers may not be able to handle. Second, pool shock rids the water of contaminants from body oils, skin and hair products, and other organic matter that can cause nasty buildup at the waterline. Finally, shocking your pool removes chloramines and bromamines, the bi-products of chlorine and bromine, respectively. Chloramines are actually responsible for that nasty chlorine smell we often associate with public pools, and neither chloramines nor bromamines are desirable in pool water.

When to Shock Your Pool

Shocking your pool at the right time is key to achieve maximum effectiveness and avoid wasting chlorine. Shock should be added in the evening, if possible, to give the chemicals time to work before they are burnt off by the sun. You will know it is time to shock your pool in the following situations:

At Pool Opening and Closing

Upon opening your pool for the season, balance the water chemistry, and then add shock to kill any contaminants that have grown over the winter and clear up any signs of cloudy pool water. Shock the pool before closing as well to help prevent the growth of algae and bacteria during the winter.

When Free Chlorine Levels are Low

Free chlorine levels refer to the chlorine in the pool that is actively “free” to do its job of sanitizing the water. This should not be confused with combined chlorine - the amount of chlorine in your pool that is used up (think chloramines) or total chlorine - the total amount of free chlorine and combined chlorine in the pool. When free chlorine levels drop below 3 ppm, it is time to shock the pool. We recommend raising free chlorine levels to about ten times the level of combined chlorine. This is called “breakpoint chlorination.”

After Rain or Wind Storms

Heavy rain and wind is likely to bring more dust, dirt, and debris into your pool water, requiring a dose of shock to kill any harmful contaminants.

After Heavy Usage

Always shock your swimming pool after heavy pool usage, such as a pool party or a busy weekend of swimming with the family. This will remove the organic contaminants brought into the water by swimmers.

When You See Signs of Algae

Regular shock treatments and good pool maintenance will usually prevent pool algae blooms, but if you do start to see algae, shock it immediately before it gets out of hand. Pool shock is a powerful algaecide.

Types of Pool Shock

  • Calcium Hypochlorite, or cal hypo, is the most commonly used type of granular chlorine shock because it is affordable and powerful. It is important to note that this type of shock can increase the calcium hardness and pH levels in your pool.
  • Di-Chlor is another popular type of chlorine pool shock that effectively removes contaminants. It does not raise pH levels in your pool water, but it does contain cyanuric acid for stability and will increase your pool’s cyanuric acid level. The addition of stabilizer makes it a popular choice for hot tubs.
  • Non-Chlorine Shock contains the active ingredient potassium peroxymonosulfate and is a popular alternative to chlorinated shock that oxidizes chloramines and removes organic contaminants in the water. Many pool owners like to use non-chlorine shock in between regular shock treatments for a chlorination boost that does not require a long wait time before swimming can resume.

Steps to Shock Your Pool

Step1

Test your water with a test kit or test strips to ensure the pH level is in the recommended range of 7.4-7.6, alkalinity is between 80-120 ppm, and calcium hardness is appropriate for the type of pool that you have. Make sure that cyanuric acid is at the proper level as well, as it acts as a chlorine stabilizer.

Step 2

Wear protective gear including gloves and safety goggles, as pool shock is harmful to skin and eyes, and don’t wear your favorite shirt, as it can also bleach your clothing. Always keep pool chemicals safely out of reach of children and pets.

Step 3

Turn on your pool pump and run your pool filter. Once you have added the shock, you want your pool water to circulate overnight to allow for even distribution of the chemicals.

Step 4

Measure your shock according to the manufacturer's directions. The amount of shock required will depend on how many gallons of water your pool holds. If you are using granular shock, it should be pre-dissolved in a five-gallon bucket before adding it to the pool.

Step 5

Add shock to the pool according to the instructions on the packaging.

Step 6

Stay out of the water until a water test shows that chlorine levels have returned to normal.

Using the right pool shock at the right time is the best way to keep harmful bacteria and algae out of your pool and prevent cloudy water. If you have any questions about our pool care products, contact our helpful experts at 800-574-7665 or visit us online at doheny.com.