10 Best Pool Shock of 2021: Review and Buying Guide

Lots of nasties lurk in our pools. Slime, feces, hairs, oils, urea, bacteria, fungi, etc., float around, waiting for the moment to unleash havoc on their soon-to-be hosts.

Unsanitary pools can be a nightmare, given that the contaminants and microorganisms cause gastrointestinal illnesses, rashes, eye irritation, persistent coughs, and so on.

Luckily, chlorine rids them all, but when its concentrations drop below a certain level, it allies with them in the form of chloramines. These compounds hold up chlorine and are responsible for the familiar smell.

The best pool shock breaks the bonds, freeing chlorine, and raising its levels to effectiveness. Chlorine-free alternatives persist in the market, but they are not nearly as effective.

Top 5 Best Pool Shock: Editor Pick’s

In this pool shock review, we have spent endless hours researching, analyzing, and testing to recommend the best pick for your purpose.

The Best Pool Shock Guide

Chlorine has oxidizing and bleaching properties, making it a powerful disinfectant. In this pool shock review, we give you an overview of what you need to for in a product before you make the decision. Let’s find out.

The Best Pool Shock Reviews:

1. Pool Essentials Shock Treatment 6 Pack (13.4 oz Bags)

Pool Essentials Shock Treatment 6 Pack (13.4 oz Bags)
  • Fast-dissolving pool shock
  • Clears cloudy water and removes swimmer contaminants* (*) such as body oils, sweat, lotions and urine
  • power_source_type: Manual
  • No assembly required

The 52008 is the best pool shock for super chlorination. It relies on the action of calcium hypochlorite (Cal Hypo) to control germs, slime, bacteria, fungi, and algae. Through oxidation, it disrupts the cellular processes of harmful microbes, resulting in death.

Cal Hypo is stable and has a long shelf life. The best pool shock on the market also contains chlorides of calcium and sodium, which release chlorine upon electrolysis. However, excess calcium chloride hardens water. And water hardness is responsible for scaling that blocks pipes and filters.

The 1.1-pound pack also contains calcium carbonate, which precipitates in alkaline pH, turning the water cloudy. You may need to add hydrochloric acid to offset the excess alkalinity. The HTH 52008 burns or oxidizes chloramines, resulting in free-floating chlorine ions, which are effective against the microorganisms when their concentration is adequate.

Euphoria comes with smelling chlorine smell. A mega dose of the powder plus shock eliminates it and inactivates the disease-causing germs. E.coli and other virulent bacteria usually lurk in pools with poor sanitation. They cause gastrointestinal illnesses.

Before dawn or dusk, every week, be sure to add the pool shock. Ensure pH levels lie in the 7.2-7.8 range, and alkalinity levels lie between 80- and 120-ppm. Water hardness shouldn’t exceed 200 ppm, according to the United States Environmental Protection Agency (EPA).

Testing kits are available in the market, and they are affordable. You don’t need expert help to use them. Chlorine can damage the vinyl liners of pools. Ensure you add a direct dose to the skimmer — not the water.

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2. hth Pool Shock Super Shock Treatment 6 count 6lbs (52008)

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When you are aware your pool contains bugs like E.coli, giardia or, cryptosporidium, you can easily forget the health benefits of swimming. As a form of aerobic exercise, swimming is beneficial. However, pools with poor sanitation are home to harmful microbes that are responsible for gastrointestinal ailments.

According to the Centers for Disease Control (CDC), while chlorine is effective against the disease-causing microorganisms, it isn’t so when it comes to sanitizing human waste. We recommend you take a pre-swim shower. Encourage your children to break for the toilet.

The 24106CLX is a potent disinfectant as long as pH levels lie between 7.2 and 7.8. It’s a source of chlorine, which is the main active ingredient responsible for killing the bugs. Clorox boosts chlorine levels because it breaks the bond between chlorine and the contaminants, leaving your pool sparkling and crystal clear.

It eliminates the familiar stench, dirt, and cloudiness. Black, yellow, and green algae have no chance against the six-pound pack of chlorinating granules. It’s not just poop that’s resistant to chlorine; some microorganisms are. Ensure you shower before you enter the pool.

Also, avoid swimming if you are still recovering from diarrhea. Chlorine doesn’t just combine with the contaminants; it can also form bonds with ammonia, with the resulting compound responsible for eye irritation.

Ultraviolet radiation from sunlight causes bleaching, which reduces chlorine levels. The halogen doesn’t last long in the water. Just be sure to switch on the filter and shock the pool during sunset or sunrise while it’s running.

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3. Pool Essentials 25106ESS

Pool Essentials 25106ESS
  • Quick-dissolving, dual action pool chlorine granules that maintains a healthy pool
  • Pool sanitizer and shock
  • Kills harmful bacteria
  • Kills and prevents all types of pool algae
  • Improves filter performance

This 13-ounce bagful of granule or tablet is the best pool shock if your pool gives off a strong chlorine odor. While chlorine smell is synonymous with fond childhood memories and swimming, it’s an indicator of the presence of chloramines, which are compounds that form when free chlorine radicals bond with contaminants from bathers such as urea, sweat, feces, hair, sunscreen, body oils, and so forth.

Such a combination is harmful because it reduces the level of the disinfectant and is responsible for eye irritation, migraine, rashes, itchy throat or nose, and bronchitis. Pool Essentials 25106ESS frees the ions, raising chlorine levels. The last thing you want when you come out of the pool is to reek of a disinfectant byproduct.

What’s good about the 25106ESS is that it increases the effectiveness of chlorine. You can be reliant on the granules to enable chlorine to eliminate most microbes, such as E.coli and other virulent bacteria that float around in the water. You don’t have to think twice before you take a dip in a pool with proper chlorination.

For best results, the National Swimming Pool Foundation recommends that you maintain a concentration of between one and four parts per million (ppm) and pH of between 7.2 and 7.8.

The leslies pool shock can also eliminate cloudiness, although clearness isn’t an indication of a bug-free pool. Be sure to maintain chloramine levels below 0.5 ppm.

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4. In The Swim Chlorine Pool Shock – 24 X 1 Pound Bags

In The Swim Chlorine Pool Shock - 24 X 1 Pound Bags
  • Powerful chlorine shock treatment that is great for regular maintenance
  • Quickly eliminates algae, bacteria, and other harmful contaminants from your pool water
  • Main active ingredient is 68% Calcium Hypochlorite (Cal-Hypo) for quick sanitizing
  • Dosage: 1 Pound per 10,000 gallons
  • Special Shipping Information: This product may not be available for 1 or 2 day shipping due to federal regulations that require it to ship via ground ship methods only. This product can only be shipped within the 48 contiguous states.

When you want to enjoy sediment- or microbe-free swimming, you require a powerful pesticide and a flocculant. As well, maintaining odorless and dirt less water is a desire of many pool owners. But pool maintenance doesn’t have to be stressful.

The Chlorine Pool Shock contains Cal Hypo as the main active compound. Cal Hypo doesn’t just eliminate algae but also bacteria, fungi, slime, and other irritants. You will require lots of chlorine to remove black, yellow, pink, or green algae, and the best pool shock is in ample supply.

The 27-pound package contains 24 bags of the chlorinating granules, with each weighing approximately one-pound. However, alkalinity increases when you add the granules. Be sure to reduce it by adding a weak acid like hydrochloric.

Calcium ions also contribute to water hardness. Use a test kit to check the level of hardness, and be sure it doesn’t exceed 200 ppm.

Optimum chlorine levels should be between one and four ppm (mg/L). You can attain the concentration in a 10,000-gallon-capacity swimming pool by adding the contents of one bag.

For best results, shock the pool every week. The package should be enough to serve you for 24 weeks (six months), but the duration will be shorter if the pool’s size increases. If your vinyl liners are present, the product will bleach them. Algaecides and stabilizers are absent. And so, you are likely to lose some chlorine after adding.

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5. Leisure Time RENU2 Renew Non-Chlorine Shock Treatment

Leisure Time RENU2 Renew Non-Chlorine Shock Treatment
  • Spa Shock Treatment
  • Clears Water
  • Eliminates Odors and Contaminents

While chlorine destroys harmful microbes by bonding with their external surfaces, it’s absent in the best pool shock for vinyl liners. Leisure Time RENU2 is a non-carcinogenic alternative to chlorine-containing disinfectants.

It works by oxidizing organic wastes, removing ammonia and chloramines, and relying on potassium salt, which makes up about 38- and 42-percent of the composition. The active ingredient takes effect immediately.

While it isn’t nearly as effective as the yellow-green gas, it spares you from the double-edged nature of the active ingredient. You also don’t have to wait for sunrise or sunset. You swim as soon as you pour the liquid.

Vinyl liners wear away, bleach, or fade when they come into contact with the granules or tables, but, with the RENU2 Renew, they are safe. Else, you have to pre-dissolve the solids — an unnecessary hassle.

You also don’t have to worry about water hardness that comes as a result of the presence of calcium ions, which come from Cal Hypo. Nor would you have to worry about cyanuric acid, which comes from dich lo ro. Also, chlorine compounds have a strong odor.

Not to mention, chlorine shocks often leave sediments that make your pool cloudy. The non-chlorine product has a longer shelf life and is safer to store than granular chlorine, especially in places where humidity and temperature levels vary like shades and garages.

The RENU2 Renew also maintains pH levels of 7.0 and thereabouts. And while the vinyl pool shock costs nearly as much as the chlorine shock treatments, it doesn’t come close to the effectiveness of its counterpart in eliminating algae and bacteria.

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6. Pool Essentials Shock Treatment 6 Pack (1 lb Bags)

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Isn’t it an irony that a product that adds three or four times the amount of chlorine you would usually add to your pool weakens the odor? Chlorine levels are inversely proportional to the strength of the smell. Chloramines are the culprits because they cause losses of the active compound.

They are products of a combination of chlorine and bather wastes like hair, sweat, oil, feces, and so on. Adding the 25506ESS restores chlorine levels. Algae and bacteria have no chance against Pool Essentials. It’s recommendable you add the pesticide once per week.

When you want to achieve the optimum level (1-4 mg/L), you need to add one pound of the Pool Essentials to a 10,000-gallon-capacity pool. However, one pack weighs one pound. Hence, the six-pack bag can last for one-and-a-half months.

But the best pool shock can last longer if you have a smaller pool and opposite with a larger. The 25506ESS purifying action comes through the oxidation of the natural wastes. The tri-chloro-s-tri-azine-tri-one has an abundance of 53.5 percent, and hence it’s the active ingredient.

While its dissolution takes place immediately, you will have to wait for half a day or longer to take a dip into the pool. Besides, the chlorine-based compounds don’t dissolve fully, leaving ‘dust’ responsible for the cloudiness it’s supposed to eliminate in the first place.

Vinyl liners can also fade or corrode in the presence of the product. Hence, you will have to fill a five-gallon-capacity bucket with pool water in the process of pre-dissolution.

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7. Spa Guard BIO42234 Enhanced Shock

Spa Guard BIO42234 Enhanced Shock
  • SpaGuard Enhanced Shock 2lb

Our pools can be murky if they don’t get proper sanitation. Plenty of harmful bugs float around in the water. This prospect can spook you.

Fortunately, the BIO42234 is a lifesaver. Sodium dichloro-s-tri-azine-tri-one is an active ingredient with an abundance of 58.2 percent. The bottle of the liquid containing the compound weighs 2-pounds.

The substance is a source of chlorine, which is hands-down the absolute best pool shock for algae and bacteria elimination. Unlike the tablet or granule pesticides, it doesn’t deposit cloudy dust, as all the liquid dissolves.

However, you will have to wait for at least 12 hours to swim. You will have to pre-dissolve the potent disinfectant in a five-gallon-capacity bucket so that swimsuits or vinyl liners don’t wear away or fade.

Also, when you use the BIO4224, you must add cyanuric acid to prevent chlorine from evaporating. But the anti-evaporation agent can accumulate to uncontrollable levels.

Cyanuric acid alters the relationship between chlorine and pH, reducing the amount of active chlorine. And a pool in which active chlorine is low isn’t effective against germs and dirt.

Be sure to maintain cyanuric acid concentrations of between 40- and 100-ppm to prevent pH imbalance and over chlorination. Excess increases the risks of gastrointestinal problems and rashes.

Spa Guard isn’t expensive, yet its rating is high. It’s not just worth considering, but it’s the best chlorine shock for pools. While it doesn’t come in sufficient quantities, it is worth every cent for anyone who wants to avoid a dreadful experience.

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8. Clorox Pool & Spa Shock Xtra Blue, 6-Pound 33006CLX

Clorox Pool & Spa Shock Xtra Blue, 6-Pound 33006CLX
  • Easy open, easy pour bottles
  • Contains blue algae killing crystals
  • Kills and prevents Green, Black and mustard algae

When algae and bacteria are a persistent nuisance in your pool, then Xtra Blue 33006CLX is a great go-to option you can find in our Clorox pool shock reviews. The whole package contains six bottles of the powder. Each weighs one pound.

Be sure to maintain chlorine levels between one and three parts per million. If murkiness and algae persist, cyanuric acid could be the problem, although it stabilizes the halogen against evaporation in sunlight.

High levels of the substance enable cryptosporidium to thrive. It doesn’t go away unless you drain the pool. But draining and refilling isn’t a viable option in water scarcity areas.  Pool waste disposal isn’t environmentally friendly.

However, biodegradable versions of the product have proved effective. Be sure to maintain acceptable chlorine levels to get the best results. With a chlorine compound as an active ingredient, Xtra Blue 33006CLX is one of the most effective types of pool shock.

And just as with any tablet, granule, or liquid, you must pre-dissolve the dich loro to avoid bleaching or fading your swimming pool liner or swimsuit. If water hardness is your concern, calcium or magnesium ions, the causative agents, are absent in the active ingredient.

However, water cloudiness is an issue with dichloro products. Dusty deposits aren’t a good sight to behold. You may have to avoid more dichloro when cyanuric levels are excess. It will take a while before you take a dip. Also, you will have to contend with strong odors if chlorine levels decline due to sunlight and cyanuric acid.

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9. Dry Tec 1-1901 Calcium Hypochlorite Chlorinating Shock Treatment

Dry Tec 1-1901 Calcium Hypochlorite Chlorinating Shock Treatment
  • 24 bags (1-pound each)
  • Fast-Acting Quick-Dissolving Swimming Pool Sanitizer
  • Kills bacteria, controls algae, and destroys organic contaminants in pools
  • 68% calcium hypochlorite
  • Recommended Dosage: 1 pound per 10,000 gallons of water

Cal Hypo is the main active compound with an abundance of 68 percent. Without a doubt, Dry Tec is highly potent against bacteria and algae. It doesn’t spare slime, fungi, and other creeps, either. Cal Hypo oxidizes compounds on the surfaces of the microbes, inhibiting vital processes in their cells and hence leading to death.

The whole package contains 24 packets, each weighing one pound. For a 10,000-gallon-capacity swimming pool, that will last about six months. The 1-1901–24 is worth the salt, as it’s adequate and lasts, and its price is reasonable.

However, with the calcium-containing compound, water hardness should be a real concern. Not to mention, water can fade, high alkalinity causes the precipitation of iron. Ensure you maintain the recommendable pH levels, and alkali concentration lies between 60- and 120-mg/L.

Unless the quantity of active chlorine lies between 1-4 ppm, don’t enter the pool. It will take half a day or longer to obtain the optimum levels. If you want to swim immediately, Dry Tec is the wrong choice.

Add cyanuric acid to maintain chlorine’s stability in sunlight. If you own a vinyl pool or you use a swimsuit, don’t add the chemical directly.

Instead, pre-dissolve it in a five-gallon container. Else, the liners will fade or bleach. When pH isn’t favorable, precipitation can contribute to cloudiness or deposition of residues or sediments.

Dry Tec is the best pool shock if you are looking for the most effective yet cheapest way to get rid of germs and dirt. It’s worth the risk if you have a pool.

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10. In The Swim Chlorine Pool Shock – 12 X 1 Pound Bags

In The Swim Chlorine Pool Shock - 12 X 1 Pound Bags
  • Powerful chlorine shock treatment that is great for regular maintenance
  • Quickly eliminates algae, bacteria, and other harmful contaminants from your pool water
  • Main active ingredient is 68% Calcium Hypochlorite (Cal-Hypo) for quick sanitizing
  • Dosage: 1 Pound per 10,000 gallons
  • Special Shipping Information: This product may not be available for 1 or 2 day shipping due to federal regulations that require it to ship via ground ship methods only. This product can only be shipped within the 48 contiguous states.

If you are looking for the best pool shock for algae and bacteria, then In the Swim fulfills your criteria. Cal Hypo is the main active ingredient with an abundance of 68 percent. It oxidizes chloramines, freeing chlorine ions.

Oxidation also disrupts the cellular functions of the harmful microorganisms that lurk in your pool. When chlorine levels increase, the pungent smell disappears. However, calcium ions increase pH and lead to the precipitation of irons, which causes the water to lose color.

The deposition of the metal leaves ‘dust’ or sediments, and the pool turns cloudy. Calcium ions also contribute to water hardness. And if you want to prevent chlorine loss through evaporation, you will need to add cyanuric acid.

But the acid is stable, building up to undesirable quantities, yet getting rid of it is cumbersome — and the last thing you want is to empty and refill your pool. And if you live in a water-scarce area, the latter option makes little sense.

Fortunately, biodegradable cyanuric acids are available in the market. The whole package is affordable and contains 12 packs, each having the contents weighing one-pound. If you’re a proud owner of the standard 10,000-gallon-capacity pool, you are in luck. The package can keep waters sparkling for three months.

However, while the chlorinating granules are highly soluble in water, you will need to wait for more than 12 hours to get the desirable range of chlorine concentration (1-4 ppm). Too much chlorine is harmful. As with any other chlorine shock, you will need to pre-dissolve the chemical to avoid bleaching the vinyl liners.

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11. HTH 42014 Super Chlorinating Tablets Swimming Pool Chlorine

HTH 42014 Super Chlorinating Tablets Swimming Pool Chlorine
  • BENEFITS: Sanitizes and protects your pool water so you can enjoy swimming all season long
  • USE: Place a tab in pool skimmer, floater, or feeder for simple, DIY pool care
  • COMPATIBILITY: Vinyl pools and saltwater systems
  • FEATURES: Easy to use; Dissolves slowly for a steady application of chlorine to your indoor or outdoor pool for up to a week
  • INCLUDES: One 35-pound pail of Chlorinating Tablets for swimming pools

If you desire the cheapest and most bountiful pool shock that can last for a long while, giving the best results, then HTH 42014 Super is heaven-sent. The full package is a ten-pound bucket, which contains 26 3-inch-diameter tablets, each of which weighs one pound.

Be sure to store the container in a cool, dry place so that the hygroscopic tablets don’t stick together, giving you a hard time to scoop with a spatula. With a once-a-week pool shocking, the product will keep your pool crystal clear for about nine months.

Trichloro-s-tri-azine-tri-one, which has an abundance of 93.6-percent, is the main compound that boosts the amount of chorine. It restores levels potent enough to get rid of the most stubborn algae and bacteria you might have ever heard of in our pool shock review.

HTH 42014 will take a long period to dissolve. The latter causes cyanuric acid to accumulate to undesirable levels. Excess of the acid interferes with how chlorine disinfects, oxidizes, or inhibits microbes.

Also, the fact that the 42014 doesn’t contain calcium ions, which contribute to water hardness, is a big plus. However, chlorine is a bleaching agent that causes vinyl liners or swimsuits to lose color.

Therefore, you need to pre-dissolve the tablet in a five-gallon-capacity bucket. Be sure to maintain pH levels between 7.2 and 7.6 to ensure that the water retains its color — and iron doesn’t precipitate, leading to cloudiness.

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12. Aqua Chem Xtra Blue 12101AQU

Aqua Chem Xtra Blue 12101AQU
  • Kills bacteria and algae
  • Creates sparkling water
  • For use in all pool types
  • Reduces chlorine odor and eye irritation
  • Will not increase pH

The Xtra Blue 12101AQU contains metal dich loro as the most abundant compound in the mixture, at 63-percent. The Xtra Blue 12101AQU is the most suitable compound if you live in water-scarce regions. When cyanuric acid and water hardness pile to unacceptable levels, draining and refilling your pool is the last thing you want to do.

While the best pool shock for water scarcity may not spare vinyl liners and swimsuits, it’s stable because one pound of the dich loro boosts cyanuric acid levels. Pre-dissolution is the way to go. Chlorine losses due to sunlight should be the least of your worries.

Available in a one-pound bag, there are five of these in the whole package. The powders are water-soluble, but you will have to wait for at least half a day to swim when chlorine levels lie between one and four parts per million.

The danger lies with high cyanuric acid concentrations, which can prompt you to drain, which isn’t feasible and environment-friendly. Even so, biodegradable options abound in the market. When chlorine amounts decrease, the familiar stench can arise again.

Creeps like fungi, bacteria, and algae have little chance against a potent pesticide. The Xtra Blue 12101AQU has what it takes to get rid of them. The whole package can last for 1-1/4 months if you use it on a 10,000-gallon pool.

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The Best Pool Shock Buyer’s Guide

The market offers an avalanche of alternatives. As always, extra features can easily carry you away. Worry not. Below. We give you some useful nuggets to guard against all the bells and whistles. Consider the following when you want to get the best pool shock:

Water Availability

Do you live where water shortage is the norm? If so, dichloro options aren’t suitable. Cyanuric acids aren’t easy to tame. Their levels will keep rising, and dichloro shocks aggravate the situation. The last thing you want is to drain and refill. Besides, disposal is environmentally unfriendly.

Type of Pool Shock

Large varieties exist, but they loosely fall into chlorine and non-chlorine derivatives. Cal Hypo is powerful, but it raises pH and hardness. On the other hand, dichloro shocks raise cyanuric acid levels. Trichloro is the cleanest alternative.

Best Pool Shock

Chlorine shocks also take time to attain the optimum level.

Type of Pool

The vinyl lining will fade with exposure to chlorine. As a powerful bleach, sunlight affects the green-yellow molecule, splitting it up. Read details


In this pool shock review, we have discussed and reviewed the picks of the best pool shock for different purposes. Chlorine versus non-chlorine options are available, but your choice depends on what type of pool your own.

Vinyl liner pools require pre-dissolution of the shock. Else, the material loses color. Chlorine-containing products come in the form of Cal Hypo and metal-dichloro or trichloro. The trichloro shocks don’t raise cyanuric acid levels, unlike dichloro, while Cal Hypo increases hardness and alkalinity.

Also, pH levels are too alkaline, iron precipitates, resulting in cloudiness. Some shocks have stabilizers, and others not. And so, be sure to check before you make the ultimate buying decision.


  1. https://www.poolcalculator.com/buying-guide-for-the-best-pool-shock/
  2. https://www.bobvila.com/articles/best-pool-shock/
  3. https://poolresearch.com/best-pool-shock/
  4. https://poolcleanerplanet.com/best-pool-shock/

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