What Is The Best Time Of Day To Shock A Pool?

Last Updated on October 20, 2021

If you’re a first time swimming pool owner, then you may be wondering how you can keep your pool clean just like those in private hotels and clubhouses. Keeping your pool clean is important to prevent cloudy water or algae buildup.

One of the ways you can keep your pool water in pristine condition is by shocking your swimming pool.

What is the best time of day to shock a pool?

The best time of day to shock a pool is when the sun is down. Doing it late evening increases the effectiveness and efficiency of your pool shock. The time of day to shock your pool is vital since the sun’s ultraviolet rays can greatly affect the amount of chlorine in your pool water. These UV rays can dissolve the chlorine quickly if it gets a chance to attach and oxidize.

Since it is advisable to shock your pool late evening, you’ll be able to leave the pool shock overnight. Depending on the pool chemicals that you’ll be using, leaving it overnight should be enough time for you to begin using your pool again.

Of course, you’ll have to make sure to test your pool water chemistry for confirmation.

When should you shock your pool?

Now that you already know when is the best time of day to shock a pool, then you might be asking how often you should be doing it. Here are some scenarios that shocking your pool will be required.

  • After heavy rainfall
  • Cloudy pool water
  • When pool water temperature rises
  • During extended periods of hot weather
  • When the free chlorine level goes below 3ppm

What does shocking your pool means?

Shocking your pool means you’ll be adding more chlorine in your swimming pool to sanitize it. This helps get rid of contaminants, chloramine, bacteria, and viruses. Adding more chlorine also prevents living organisms (like algae) from thriving in your swimming pool.

How do you shock your pool?

Shocking your pool can be a tedious process, so it is important for you to have the proper equipment for your own safety. You can follow this step-by-step guide on how to shock your pool to make sure you’ll be doing everything right.

Step-by-Step Guide To Shocking Your Pool

1. Protect yourself

Shocking your pool can harm your skin if exposed to pool chemicals, so make sure you wear protective gear like safety goggles, gloves, and proper clothing. We advise using old clothes as shocking your pool may bleach your clothing.

2. Prepare your pool chemicals

There are different types of pool chemicals you can use to shock your pool. Be sure to read the instructions that come with the product and prepare it accordingly.

3. Pour the chemicals into your pool

Once you’re done preparing your pool shock, it’s time to pour it into your pool. You may pour it on your pool jets or you may have to disperse it evenly around your pool edges.

You may refer to your pool shock instructions for the best recommendation on how to pour your pool shock.

4. Wait

After pouring your pool shock, you must wait for the pool chemicals to do their job. Make sure that no one gets in the water too soon to avoid any injuries.

5. Check your pool water chemistry

You have to test your pool water chemistry to be certain that everything’s back to normal and it’s safe to use your swimming pool.

6. Turn on your pool filter

Once everything settles down, you can start running your pool filter to get rid of all the contaminants on your swimming pool after you shock it. Make sure you run it for at least 24 hours to make sure it cleans all the matter in your pool.

Different Shock Treatments: Chlorine vs Non-Chlorine

Cal-Hypo Pool Shock

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Calcium Hypochlorite, or commonly referred to as “Cal-Hypo”, is the most common chemical pool shock used to disinfect swimming pools. This pool shock kills both bacteria and algae in your swimming pool.

Most cal-hypo pool treatments contain 65% or more chlorine. The average time before safely entering the pool is 8 hours.


Doheny's Di-Chlor Granular Chlorine | Pro-Grade 3-in-1 Pool Chlorine Granules Sanitizer, Shock and A
  • Multi-Purpose Swimming Pool Chlorine: 3-in-1 pool chlorine granules help sanitize, shock, and eliminate algae from your pool
  • Fast-Dissolving Granular Chlorine: Non-cloudy calcium-free formula creates no residue and leaves only crystal-clear water behind
  • Recommended Dosage: Add 1 lb of granular Di-Chlor per 10,0000 gallons of pool water to maintain proper chlorine levels
  • Ingredients: This granular pool chlorine contains 99.5% Sodium Dichloro-S-Triazinetrione with premium-quality 56% available stabilized chlorine

Dichloroisocyanuric acid or “Dichlor” is also used as a chemical pool shock treatment mostly for residential pools. Dichlor contains around 50% chlorine. The average wait time before safely re-entering your pool is about 8 hours.

Non-chlorine shock

GLB 71414A-20 Oxy Brite, 1-Pound, 20-Pack
  • For more than 30 years, oxy-brite has offered a non-chlorine alternative for shock oxidizing pool water
  • In addition to its effective shock oxidation treatment, oxy-brite includes unique blue water brightening crystals that polish the water
  • Swim immediately after treatment

Non-chlorine pool shock treatments are used by those who rush to use their pool after treating it. The most common ingredient in non-chlorine pool shock treatments is potassium monopersulfate, and this shock treatment does not contain chlorine.

The main advantage of non-chlorine shock is instead of waiting eight hours for safe swimming, you only have to wait about 15 minutes.

The disadvantage of using non-chlorine shock is that because there is no chlorine in the ingredients, it doesn’t work as well on getting rid of algae in your pool.

Final Thoughts on Shocking Your Pool

Shocking your pool kill is vital in properly maintaining your swimming pool. You should remember how often you should shock your pool. Knowing the best time to shock your pool is important for effective pool maintenance.

Frequently Asked Question When Shocking A Pool

How long does it take for a pool to clear up after you shock it?

The wait time depends on the type of chemical that’s used and how much of it is used in relation to your pool size. The best way to know is by using test strips that measure the chemicals in your swimming pool.

Should the filter be on when shocking pool?

No, you should not run your filter when shocking your pool. Run it after you’re done pouring your pool shock. This way the contaminants can be filtered by your pool filter system.

Since the best time of day to shock a pool is late in the evening, turn your pump and filter on before you go to bed, so it can keep the pool water circulated and filtered. Everything should be ready in the morning.

What happens if you swim in a shocked pool?

Swimming in a recently shocked pool can cause severe skin and eye damage, so it’s best to test your pool water chemistry before using your pool after shocking it.

Can you over shock a pool?

No, you cannot over shock your pool.

But it’s advisable to follow the instructions by your pool shock manufacturer, so you’ll know the right amount to use. Using too much pool shock would not damage your pool, it will just prolong your waiting time before you can use your pool again.

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