Cloudy Pool Water After Shock and Algaecide

In the world of Swimming Pools and Spas, the problem you think you have can be answered by a simple test kit or a simple explanation, like Why there is a change of color in your pool water or Why Does My Pool look Cloudy after Shocking it?

The cloudiness in the pool after shocking is normal, should only last an hour or so & is due to the reaction of dissolving crystals, salts, and inert materials like Calcium and Cyanuric Acid found in Calcium Hypochlorite based Shock Chlorine products.

There are different types of Shock Chlorine on the market today but the most common and strongest is Cal-hypo or Calcium Hypochlorite which contain other ingredients that help it do its thing. 

Is Pool Shock the Same as Chlorine

If you are using chlorine tablets in your swimming pool, you won’t be used to seeing the burst of granular chlorine dissolving in your pool. The 3″ tablets that are used in the floaters are meant to dissolve very slow and keep the sanitizing at a pace where they are easier to maintain. The pool operator (that would be you)  will have less work to do.

Granular Chlorine can the most effective Chlorine to use especially in bigger concrete pools where there is no danger of chlorine settling to the bottom of the pool and damaging the paint or surface. I personally like seeing the cloudiness in the pool that represents the mix and the area that the Shock is covering. Adding the Shock Chlorine at night with pool light on gives me a reliable feeling that I am applying and broadcasting the Shock in an appropriate manner covering the surface area of the pool.

If your Pool Water isn’t cloudy before you add the shock Chlorine to the pool than the cloudiness has more to do with the Shock Chlorine than the chemistry in your swimming pool.

There could be various reasons why your pool water turned cloudy.

  • The initial reaction of the granular hitting the pool and dissolving. Most quality Granular Chlorine contains fast-dissolving crystals.
  • Most Shock Chlorine is Calcium Hypochlorite pool shock and is made with Calcium and if your pool water is slightly on the hard side it might have a cloudy effect.
  •  All Granular Chlorine like Shock Chlorine contains inert material that comes out when diluted in your pool especially at night under the pool light. You are Shocking your pool at night, aren’t you?
  • Use the best Shock Chlorine by reading the label on its container.
  • There is another ingredient that can temporarily cause a small amount of cloudiness cyanuric acid can come out of solution when very high. Test your cyanuric acid (stabilizer) level every month or two to be sure that it doesn’t rise above 50 ppm.

How long will your pool stay cloudy after you shock the pool?

After the initial reaction of the Shock Chlorine, the cloudiness and oxidation will last a short while as the water dissolves the salts and crystals in the contents of the Calcium Hypochlorite which is the most common, strongest and cheapest oxidizer, available in two strengths, Shock and Super Shock. A good Calcium Chlorite Product recommended by MyWaterEarth&Sky is Zappit 73% Cal Hypo Pool Shock – Calcium Hypochlorite Super Shock 50lb sold through Amazon at a great price!

Leaving your filter on will circulate the pool and eventually dissolve the inert ingredients, calcium, and binders that are used in the product. 

 Best Pool Shock

The best Chlorine and Shock Chlorine to use is the most powerful. You can get this information printed on the packaging. With Granular Sodium Hypochlorite Shock, there are 2 strengths. Regular Shock and Super. On the back of the bag check for listed ingredients. A 1 lb bag is common:

  • Regular Shock-Active Ingredient-Sodium Hypochlorite-Maximum Percentage is usually around 68 %
  • Other Ingredients or Inert Ingredients is around 62%
  • Available Chlorine– around 65%

Super shock contains more chlorine than any other swimming pool shock formula and also acts faster to kill contaminants. This type of Shock is generally used for start-up or when there is visual cloudiness or algae that has already started in the pool.

  • Super Shock- Active Ingredient is Sodium Hypochlorite- AC or Available Chlorine is around 68- 73%-Other Ingredients are 27%-Each 1 lb bag is a dosage for 10,000 gallons  

Use a Pool Chemical Calculator for the best results and for saving money like this one. 

Calcium Hypochlorite is commonly seen as granular Chlorine but also is in tablet form. Calcium Hypo has an AC of 40-78% and it the most popular of the Chlorines.  Calcium Hypo is used regularly in both home and commercial pools and is usually what is seen on your local mart shelves.
The difference between the Calcium Hypochlorite sold in pool stores versus local mart stores is the AC level or the Available Chlorine that is written on the package. Remember: the higher the AC level the more disinfectant is going into your pool.

Sodium Hypochlorite is a liquid Chlorine and has around 10-12% Available Chlorine. If you’re dealing with a liner than you may want to use this Bleach sanitizer but otherwise, I don’t recommend it.

If you have a concrete or cement pool you don’t need to mix any kind of Chlorine to add to your pool. When you mix it you activate it. You lose some of the punch it has.

Use a Fast Dissolving Granular Shock Chlorine. In fact, I use Granular Chlorine for regular maintenance Sanitizing and Shocking. 

Jim has worked in Water/Wastewater and Water Filtration Business as a Consulting Operator for 30 years and has written more than 300 articles on the Worldwide Water Situation.


Author/Editor, MyWaterEarth&Sky

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