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!
| Model | What makes it the best |
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. Jump to the detailed review |
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. Jump to the detailed review |
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. Jump to the detailed review |
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. Jump to the detailed review |
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. Jump to the detailed review |
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.
| 2 PPM - parts per million. 1 ppm = 0.000001%. 2 ppm is the minimal normal level of chlorine. | 5-10 These levels are needed to reach to kill a large number of algae and bacteria. | |
| 73% calcium hypochlorite | 1 lb per 40,000 gallons | 2.5lb per 40,000 gallons |
| 68% calcium hypochlorite | 2.5lb per 40,000 gallons | 5lb per 40,000 gallons |
| 56.4% calcium hypochlorite | 3lb per 40,000 gallons | 6lb per 40,000 gallons |
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.
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 is the total mass of chlorine contained in a substance, which can be released when this substance reacts with hydrochloric acid. When disinfecting water by chlorination, the free active chlorine contained in the water reacts with organic (amino acids, etc.):
To shock the pool, you will need the following amount of these chemicals per 10,000 gallons of water:
| Name | Bleach | Liquid chlorine | 56.4% calcium hypochlorite | 68% calcium hypochlorite | 73% calcium hypochlorite |
| Amount | 150 oz | 102 oz | 12 oz | 10 oz | 4 oz |
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.
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.
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% |
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.
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% |
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.
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!
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% |
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.
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.
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% |
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.
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% |
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.
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.
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.
| Name | Liquid | Powder and granular |
| Characteristics | Available 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. |
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 - parts per million. 1 ppm = 0.000001%..
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.
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.
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:
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.
Liquid chlorine has 10-12% active chlorine, while calcium hypochlorite has 50-70%. Therefore, the second you need to use less than the first.
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.
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.
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.
Alternatives to pool shock are salt systems, mineral sanitizers, and UV ozone systems.
Multiple medical studies warn that improper use of hot tubs can lead to birth defects. Find out how to minimize…
Are you confused by the sheer amount of chemicals for inflatable hot tubs? We gathered a simplified list of the…
Our team has analyzed top-5 generators to help you choose the best one. With a salt chlorine generator, you’ll love…
An engineer's approach to converting your hot tub to saltwater – Check our 5-step guide on how to do it…
Presenting you 30+ fun accessories to enhance your hot tub experiences with family and friends! These little extras are surely…
Are you considering purchasing a hot tub chemical kit to avoid the confusion of buying 10+ different items separately? Here…