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Home Pools Pool Chemicals 5 Best Pool Shock Treatments to Keep Your Pool Water Clean

5 Best Pool Shock Treatments to Keep Your Pool Water Clean

Expert opinion on the 5 best pool shock treatments from Peter Rossi, a hot tub designer with 10+ years of experience. Choose the best one for you.
Best pool shock

Perhaps every pool owner has faced the problem of cloudy/green water or an unpleasant odor. Most often, this happens during the opening or closing of the pool. However, this can occur even during the bathing season. A pool shock can help eliminate such problems.

Pool shock is a procedure during which you should add a double or triple dose of a chlorine-containing chemical to kill large amounts of debris or algae at once. However, you may have difficulty choosing the most suitable chemical because there are many different options. Moreover, there has been a lot of debate among pool owners about whether to use liquid chlorine or calcium hypochlorite.

Therefore, we decided to delve into this topic and find out which pool shock is the best, how to choose it, how much to add, and how often to use it. Let’s get started!

 💡 Note
The cause of the green water is the large amount of algae. You can effectively deal with them using the pool algaecide. You can find the best of them in our article.

5 Best Pool Shocks Comparison Table

ModelWhat makes it the best

HTH Pool Shock Advanced
Winner in the category
The best in cleaning cloudy/green pool water
Characteristics

Amazon rating: ⭐️ 4.7
Item form: granular
Item weight: 12 pounds
Consumption: 1 pound per 13,500 gallons
Compound: 56.4% calcium hypochlorite
Active chlorine level: 56.4%

What makes it the best

The best in cleaning cloudy/green pool water – allows you to eliminate cloudy/green due to the 4-in-1 formula based on 56.4% calcium hypochlorite;

The most reduced chlorine odor – reduced unpleasant odor due to 56.4% active chlorine;

The most suitable for different pool finishes – reduced active chlorine level will not spoil pool finishes;

No chlorine lock – cyanuric acid is absent in the formula;

Total dissolving – the granules do not settle to the bottom.

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Nazhua Zappit Pool Shock
Winner in the category
The best in killing algae
Characteristics

Amazon rating: ⭐️ 4.7
Item form: granular
Item weight: 50 pounds
Consumption: 1 pound per 40,000 gallons
Compound: 73% calcium hypochlorite
Active chlorine level: 70%

What makes it the best

The best in killing algae – allows you to eliminate all types of algae (even mustard ones) due to the highest 73% calcium hypochlorite and 70% active chlorine levels;

The most giant pack – 50 lbs pack allows you to buy it once and use it for a very long time;

The most effective chlorine level raising – allows you to use 1.2 times less pool shock to yield 5-10 ppm;

Handy reference guide;

Fast dissolving – totally disappears in water in 30 minutes.

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Doheny's Chlorine Super Shock
Winner in the category
The most economical in use
Characteristics

Amazon rating: ⭐️ 4.7
Item form: granular
Item weight: 1 pound
Consumption: 10 oz per 10,000 gallons
Compound: 68% calcium hypochlorite
Active chlorine level: 65%

What makes it the best

The most economical use – allows using only 10 oz per 10,000 gallons, which is 1.6 times less than other pool shocks;

The most enduring result – allows using 1 dosage less than once a week;

The safest for available chlorine in your pool – a stabilizer that can lock chlorine is absent;

Easy to store – has a waterproof package;

Keeps algae in check – allows you to eliminate even black algae.

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DryTec Calcium Hypochlorite Shock
Winner in the category
The fastest cleaning rate
Characteristics

Amazon rating: ⭐️ 4.6
Item form: granular
Item weight: 1 pound
Consumption: 1 pound per 10,000 gallons
Compound: 68% calcium hypochlorite
Active chlorine level: 65%

What makes it the best

The fastest cleaning rate – turns your pool crystal clear within 12-24 hours, which is up to 2 times faster than others;

The most universal – allows you to disinfect even the drinking water;

The most balanced formula – allows you not to worry that levels will be imbalanced;

Clear instructions – allows you to properly use a pool shock due to the mentioned water levels;

As much as you need – available in different weights: 1, 12, and 24 pounds.

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In The Swim Chlorine Pool Shock
Winner in the category
The easiest to use
Characteristics

Amazon rating: ⭐️ 4.7
Item form: granular
Item weight: 1 pound
Consumption: 1 pound per 10,000 gallons
Compound: 68% calcium hypochlorite
Active chlorine level: 65%

What makes it the best

The easiest to use – allows you to unpack an item and add it to the pool straightaway due to its convenient weight of 1 pound, which is required for 10,000 gallons;

The safest for CYA levels – CYA is absent in the formula;

The best for adding hardness – allows you to raise pH;

Forget about algae – clears green water due to 68% calcium hypochlorite, which effectively kills algae;

Fast cleaning rate – cleans the pool as fast as the best one in this criteria.

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How to Choose the Best Pool Shock?

How to Choose the Best Pool Shock?

Of course, the best product is the one that best performs its primary job of making cloudy/green water crystal clear. However, besides this, other factors influence the choice: economy and cleaning rate. Let’s deal with them in more detail.

  • Efficiency. The best pool shock should clean the water! It sounds simple, but it’s true. The chemical is ineffective if you add the specified amount of pool shock and do not see the effect. Luckily, we have already reviewed 15+ products and 500+ reviews and gave you a verdict so that you can choose the most effective product.
  • Economical use. The less pool shock you need to add, the longer the pack will last. The table below indicates how much calcium hypochlorite you should add due to the different concentrations of the active element.
2 ppm5-10 ppm
73% calcium hypochlorite1 lb per 40,000 gallons2.5lb per 40,000 gallons
68% calcium hypochlorite2.5lb per 40,000 gallons5lb per 40,000 gallons
56.4% calcium hypochlorite3lb per 40,000 gallons6lb per 40,000 gallons
  • Cleaning rate. The best pool shock should clear the pool water in 12-24 hours, so you don’t have to wait days for the effect.

When choosing the best pool shock, compare these indicators with those of the chemical you are considering. If it matches them, you have found the perfect candidate.

How Much Pool Shock Do I Need to Add?

 Pool Shock

You can shock the pool using three chlorine-containing chemicals: bleach, liquid chlorine, and calcium hypochlorite. Their difference is that each of them has a different level of active chlorine:

  • Bleach – 5-6% chlorine;
  • Liquid chlorine – 10-12% chlorine;
  • Calcium hypochlorite – 50-70% chlorine.

To shock the pool, you will need the following amount of these chemicals per 10,000 gallons of water:

NameBleachLiquid chlorine56.4% calcium hypochlorite68% calcium hypochlorite73% calcium hypochlorite
Amount150 oz102 oz12 oz10 oz4 oz
💡 Note:
Are you surprised we mentioned bleach as one of the ways to shock the pool? Check out this article to learn about the benefits of bleach use for your pool.

5 Best Pool Shocks To Make a Pool Water Crystal Clear

The time has come to choose the best pool shock. We reviewed 15+ products, identified 10 (with 4+ Amazon ratings and 100+ reviews), and applied the QC methodology.

ByRossi® analysis methodology
ByRossi® analysis methodology

According to QC, we have selected the five highest-rated products and have detailed each below. Therefore, we suggest that you immediately proceed to familiarize yourself with them.

💡 Note:
Before shocking the pool, you need to measure the levels of chlorine and other elements in the water to avoid overdosing or ineffective results. In this case, you will need test kits which you can find in our article.

HTH Pool Shock Advanced – the best in cleaning cloudy/green pool water

The best in cleaning cloudy/green pool water

CharacteristicsAmazon rating: ⭐️ 4.7
Item form: granular
Item weight: 12 pounds
Consumption: 1 pound per 13,500 gallons
Compound: 56.4% calcium hypochlorite
Active chlorine level: 56.4%

HTH Pool Shock Advanced is the best in clearing green and cloudy pool water. This chemical contains 56.4% calcium hypochlorite and effectively eliminates bacteria, algae, and even organic pollutants such as hair, leaves, dandruff, and lotions. It is because chlorine destroys the shell of unwanted objects, gets inside, and eliminates them.

Moreover, 56.4% calcium hypochlorite causes a low level of active chlorine of 56.4%. For this reason, HTH Pool Shock Advanced has the most reduced odor among the best chemicals. 40% of users note it, which is the highest among other chemicals. Also, this product, like In The Swim Chlorine Pool Shock, does not contain cyanuric acid. So you don’t have to worry about getting too high of this and your chlorine becoming ineffective.

Another benefit of the HTH Pool Shock Advanced is that it is compatible with all pool finishes. This pool shock dissolves and leaves no residue that can bleach pool finishes.

Verdict:
 HTH Pool Shock Advanced is a highly effective chemical. At the same time, it does not harm pool finishes and does not have a bad smell. However, these benefits are based on the lower levels of calcium hypochlorite. Therefore, you need to use 1.2-3 times more of this pool shock than the others.

Pros

  • The most suitable for different pool finishes – allows you to use pool shock even in pools with vinyl liners due to reduced active chlorine level;
  • The most reduced chlorine odor – allows you not to suffer from unpleasant odor due to 56.4% active chlorine, which is 8.6-13.6% less than other pool shocks;
  • Total dissolving – the granules dissolve and do not settle to the bottom, so you will not notice bleaching marks on the pool finishes;
  • No chlorine lock – allows you not to worry that chlorine will become useless because shock does not contain cyanuric acid.

Cons

  • Users admit that due to the 56.4% calcium hypochlorite, they may need more than 1 pound per 13,500.

Nazhua Zappit Pool Shock – the best in killing algae

The best in killing algae

CharacteristicsAmazon rating: ⭐️ 4.7
Item form: granular
Item weight: 50 pounds
Consumption: 1 pound per 40,000 gallons
Compound: 73% calcium hypochlorite
Active chlorine level: 70%

Nazhua Zappit Pool Shock is the ultimate algae killer. This chemical contains 73% calcium hypochlorite and 70% available chlorine. Therefore, it can destroy the shell of even the most adaptable mustard and black algae. 

Moreover, the detailed instructions will help you to use this pool shock even more effectively, as it contains tips on pool maintenance and measuring its volume.

💡 Note
You should use all chemicals in the strictly stated dosage to avoid unwanted changes in levels. Therefore, you need to know your pool volume. Otherwise, we advise you to read our article to understand how to measure the pool volume.

Also, the Nazhua Zappit Pool Shock has the most giant pack at 50 pounds. It is 4.2 times more than the HTH Pool Shock Advanced, which is second in this indicator. Combine this with the fact that you only need to use 4 ounces per 10,000 gallons to maintain a normal free chlorine level of 2-4 ppm, and you get that one package will be enough to shock 2,000,000 gallons of water!

Verdict:
Nazhua Zappit Pool Shock works best when killing green, mustard, and black algae. It also has the most giant pack, allowing you to shock your pool up to 200 times. However, due to the high levels of calcium hypochlorite, it will settle to the bottom and may bleach the pool finish. Therefore, you should keep a close eye on it and constantly stir the chemical in the pool.

Pros

  • The best in killing algae – allows you to eliminate all types of algae (even mustard ones) due to the highest 73% calcium hypochlorite and 70% active chlorine levels;
  • The most giant pack – 50 lbs pack is 4.1-50 times larger than others, so you can buy it for a very long time;
  • The most effective chlorine level raising – you need 1.2 times less pool shock to yield 5-10 ppm of available chlorine due to the 70% pool shock’s available chlorine level;
  • Handy reference guide – allows you to easily apply it due to containing the dosage, application method, additional instructions for pool care, and pool capacity determination.

Cons

  • You should stir it because it can bleach the pool’s finish during dissolving.

Doheny’s Chlorine Super Shock – the most economical in use

The most economical in use

CharacteristicsAmazon rating: ⭐️ 4.7
Item form: granular
Item weight: 1 pound
Consumption: 10 oz per 10,000 gallons
Compound: 68% calcium hypochlorite
Active chlorine level: 65%

Doheny’s Chlorine Super Shock is the most economical chemical. It requires only 10 ounces per 10,000 gallons, which is 1.6 times less than other pool shocks with 68% calcium hypochlorite. Moreover, this chemical won’t make you worry about overdosing like Nazhua Zappit Pool Shock, as it has 65% active chlorine versus a minimum of 70% that has another one.

Also, Doheny’s Chlorine Super Shock, like HTH Pool Shock Advanced, does not contain cyanuric acid. This chemical is a stabilizer component that protects chlorine from being destroyed by ultraviolet light. However, too much of it can cause chlorine to become ineffective, so you should balance all levels.

💡 Note:
To balance levels effectively, you should use test kits. You can get acquainted with the best products in our article.

Finally, it is worth adding that this pool shock is very easy to store. Its packaging is 100% waterproof. Therefore, it keeps water out of pool shock, as it may lose its pool-cleaning properties and become ineffective.

Verdict:
Doheny’s Chlorine Super Shock formula allows it to be the most economical chemical available. It can also eliminate cloudy/green water and algae effectively but in killing mustard or black algae it can be less effective.

Pros

  • The safest for available chlorine in your pool – allows not worrying that available chlorine in the pool becomes useless due to the absence of a stabilizer that can lock chlorine;
  • The most enduring result – you can use 1 pound less than once a week due to the 68% calcium hypochlorite which eliminates bacteria, algae, and even organic contaminants;
  • Keeps algae in check – allows you to eliminate even black algae that can set into hard-to-reach areas due to the high calcium hypochlorite level;
  • Easy to store – allows not worrying that water gets into the package and spoils pool shock due to its waterproofness.

Cons

  • You need to distribute this evenly over the pool, otherwise sediment may remain on the bottom, which can bleach the pool’s finish.

DryTec Calcium Hypochlorite Shock – the fastest cleaning rate

The fastest cleaning rate

CharacteristicsAmazon rating: ⭐️ 4.6
Item form: granular
Item weight: 1 pound
Consumption: 1 pound per 10,000 gallons
Compound: 68% calcium hypochlorite
Active chlorine level: 65%

DryTec Calcium Hypochlorite Shock has the fastest cleaning rate. This chemical allows you to clear cloudy and green water from the pool in 12-24 hours, which is two times faster than other products. Moreover, the increased cleaning rate has no side effects as this chemical has a balanced formula that doesn’t harm levels.

Also, you can choose among three packs available: 1, 12, and 24 pounds. It is convenient because one pound is enough to handle 10,000 gallons like the In The Swim Chlorine Pool Shock can. Thus, if your pool is of such a volume, you can purchase one pack. Otherwise, you can pay 2.9-3.34 times less when buying a 12 or 24 than if you purchase each separately.

Additionally, we should note that this pool shock can purify drinking water. On the product packaging, you will find detailed instructions on how to clean and how much DryTec Calcium Hypochlorite Shock you should add.

Verdict:
DryTec Calcium Hypochlorite Shock has the fastest cleaning rate. It performs its duties up to two times faster than other pool shocks. However, you should add this pool shock to the skimmer, as it cannot dissolve on its own. Otherwise, you should stir the water for 20-30 minutes if you are adding this to a pool.

Pros

  • The most balanced formula – allows you to use 1 pound per 10,000 gallons dosage and not to worry that levels will be imbalanced;
  • The most universal – allows you to disinfect even the drinking water due to the calcium hypochlorite presence and availability of specialized instructions;
  • Clear instructions – allows you to properly use a pool shock due to the mentioned water levels which will provide the maximum effect of the super chlorination;
  • As much as you need – you can choose 1, 12, and 24 pounds packages.

Cons

  • For the granules not to settle to the bottom, it is better to add this to the skimmer or directly to the pool but stir constantly.

In The Swim Chlorine Pool Shock – the easiest to use

The easiest to use

CharacteristicsAmazon rating: ⭐️ 4.7
Item form: granular
Item weight: 1 pound
Consumption: 1 pound per 10,000 gallons
Compound: 68% calcium hypochlorite
Active chlorine level: 65%

In The Swim Chlorine Pool Shock is the easiest chemical to use. You can buy it, open it, and immediately add it to the water. You don’t need to dilute it in a bucket or weigh it to add a certain amount, as one packet is enough to treat 10,000 gallons.

Also, In The Swim Chlorine Pool Shock is free of CYA, as is Doheny’s Chlorine Super Shock. Thus, if you add too much, the chlorine will not become useless. Moreover, you can increase the pH levels since calcium hypochlorite has a pH of 10.2.

💡 Note:
ТIf you will raise the pH too much, you will need to lower it. In such a case, you can use muriatic acid. You can find a detailed guide on how to lower pH with muriatic acid.

It is worth noting that In The Swim Chlorine Pool Shock has the same cleaning rate as DryTec Calcium Hypochlorite Shock. Thus, you can clean the pool in 12-24 hours, which is twice as fast as other chemicals.

Verdict:
In The Swim Chlorine Pool Shock is the easiest chemical to use. You can add this to the water right after unpacking. However, you should be aware that it can increase pH. Therefore, don’t forget to check levels using test kits.

Pros

  • The best for adding hardness – allows you to raise pH due to the calcium hypochlorite which pH is 10.2;
  • The safest for CYA levels – allows not to affect these levels which can reduce the chlorine efficiency due to the CYA absence in the formula;
  • Forget about algae – 68% calcium hypochlorite can effectively eliminate green, mustard, and black algae;
  • Fast cleaning rate – cleans the pool in 12-24 hours like a shock with the highest cleaning rate.

Cons

  • Raising the pH level is a very useful feature. However, you should carefully monitor the levels so that you do not have to stabilize them later.

Which Pool Shock Type Is the Best: Liquid vs. Granular vs. Powder

When choosing chemicals, pool owners can be confused because there are three types of pool shock: liquid, granular, or powdered. The second and third types are the same. Their only difference is the form – powder and granulation respectively.

Next, let’s find out their pros and cons and make a long-awaited verdict: which pool shock is the best.

NameLiquid
Liquid
Powder and granular
Powder and granular
CharacteristicsAvailable chlorine: 10-12%
Shelf life: 4-6 weeks
Possibility to order online: No
pH level: 13
Presence of cyanuric acid: No

Available chlorine: 56-70%
Shelf life: 5-8 years
Possibility to order online: Yes
pH level: 9
The presence of cyanuric acid: Sometimes (indicated in the composition)

Pros✅ Chlorine is available immediately, so you only need to wait about 4 hours;
✅ Completely dilutes in water;
✅ Does not increase calcium hardness since it does not contain cyanuric acid.

✅ More free chlorine, so you need to add 8.5-22.5 times less than liquid chlorine;
✅ Stored for up to 8 years;
✅ You can swim 15 minutes after application;
✅ Can be ordered online;
✅ The pH is 9, so it will hardly affect the levels in your pool;
✅ Comes in waterproof packaging, so easy to store.

Cons❌ Shelf life is 4-6 weeks, after which chlorine becomes ineffective, so it is difficult to store and order online;
❌ Very high pH levels can harm pool levels;
❌ Household liquid chlorine has many contaminants that can harm water levels, and specialized pool chlorine is hard to find in stores.

❌ Some products contain cyanuric acid, which can destabilize hardness levels;
❌ Sediment may remain at the bottom, which must be constantly stirred so that it dissolves;
❌ The water will become clean in 12-24 hours, which is 3-6 times slower than liquid chlorine.

How Often Should I Use Pool Shock?

How Often Should I Use Pool Shock?

At first glance, it may seem that pool shock is an irregular procedure as it is done to kill bacteria and algae once. However, another purpose of this procedure is to maintain a normal level of chlorine in the water, which is 1-4 ppm.

And so, to maintain normal chlorine levels and keep the pool sanitized, you need to shock it once a week. On average, you only need to add 4-12 ounces per 10,000 gallons. We described in more detail how much shock to add earlier in the article.

How Long to Wait After It?

Calcium hypochlorite pool shock manufacturers claim that it is possible to swim in 15 minutes after using it. However, it is best not to do this, as chlorine levels can exceed five ppm. In this case, you may experience skin irritation.

Therefore, you should wait up to 4 hours and have your chlorine levels measured. If they are less than five ppm, you can swim in the pool and not worry about getting irritated.

💡 Note:
To accurately measure chlorine levels and protect yourself from irritation, use one of the best test kits listed in this article.

Summary

Best pool shock

It’s time to take stock. Pool shock is a regular procedure that allows you to maintain the required chlorine level and disinfect the water. To make it easier for you to choose a remedy for this procedure, we have compiled the top five pool shocks that are winners in the following categories:

  • The best in cleaning cloudy/green pool water;
  • The best in killing algae;
  • The most economical in use;
  • The fastest cleaning rate;
  • The easiest to use.

Also, we explained how you can choose the best pool shock for you, how much to add to the water, and how long to wait before swimming.

💡 Note:
Have you already shocked your pool? It’s time to finally swim in the pool with a new slide to level up the fun!

FAQ

💪 Is a pool shock stronger than chlorine?

Liquid chlorine has 10-12% active chlorine, while calcium hypochlorite has 50-70%. Therefore, the second you need to use less than the first.

1️⃣ What should I use first: pool shock or chlorine?

Chlorine and a pool shock are used for one purpose: to increase chlorine levels and kill bacteria/algae. Therefore, you should use either this or that.

⚠️ What will happen if I over shock the pool?

In this case, your pool may have a lot of algae because an excess of chlorine will create a pleasant environment for algae to grow.

🧐 Why is my pool water still green after shock?

If your water has a lot of copper, it can oxidize due to the chlorine in the shock and create a pleasant environment for algae to grow.

❓ What alternatives exist for pool shock?

Alternatives to pool shock are salt systems, mineral sanitizers, and UV ozone systems.

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