When the cold weather comes, you close the pool by emptying most, if not all, of the water and covering it. Once warm weather beckons, it’s time to fill the pool and treat the water with a pool shock treatment to get rid of any potentially dangerous microorganisms. Most pool shock products rapidly increase the chlorine level in the water, altering the pH enough to kill any invisible bad guys. The filtration system then pulls the bugs and plant life out of the water, ensuring that it’s clean for swimming. Instead of chlorine, some pool shock treatments use potassium monopersulfate, a more effective solution for saltwater pools.
You’ll likely choose a product based largely on whether your preferred form is liquid, powder, or tablet, but you should also take into account the current pH level of the water. Avoid using a swimming pool with a pH level lower than 7, as this acidic solution can cause itching, burning, and rashes. Water with a pH balance above 7.8 is also dangerous because the basic solution can burn and irritate the eyes.
To find the right pool shock treatment for your home, read on for more important info, and find out why the following products are considered among the best on the market.
- BEST OVERALL: HTH 52028 Ultimate Shock Treatment Swimming Pool
- BEST BANG FOR THE BUCK: DryTec Calcium Hypochlorite Chlorinating Shock
- BEST POWDER: Zappit 73% Cal Hypo Pool Shock
- BEST LIQUID: Austin’s 000176 Pool Tech Shock Gal. 12.5%
- BEST TABLET: HTH 42033 Super 3″ Chlorinating Tablets Swimming
- BEST SPA AND HOT TUB: SpaGuard Enhanced Shock (2 lb)
- BEST SALTWATER POOL: In The Swim Chlorine-Free Oxidizing Pool Shock
What to Consider When Buying the Best Pool Shock
Pool shock treatments are specifically formulated to kill microorganisms by rapidly increasing the chlorine level so water will be clean and healthy for the first swim of the year. To choose a product, consider pool shock type, chlorine level, and other important factors detailed below.
Pool shock products come in three main forms: powder, liquid, and tablet.
- Powder pool shock treatments typically come in a pouch or a bucket with a measuring scoop to help ensure the correct amount of product is used. This form of pool shock can either be added directly to the pool water or premixed before adding to avoid damage to a pool liner. Refer to the manufacturer’s directions before use. After treatment, it will usually take about 24 to 48 hours before the pool is safe for swimming.
- Liquid pool shock treatments are poured into the pool water and should immediately disperse, so there is no waiting for the powder or tablet to dissolve. Liquid pool shock treatments typically use a concentrated sodium hypochlorite solution. In its concentrated form, it can damage clothing and burn skin, so it’s important to be careful while measuring and pouring. Liquid pool shock products are generally less expensive than powder products.
- Tablet pool shock treatments have the slowest applications. Each tablet will usually take about 1 to 2 hours to completely dissolve in the water and it can take up to 48 hours for the pool to be ready for safe swimming.
The level of chlorine refers to the amount of chlorine present in a pool shock treatment. This amount is typically given as a percentage and is normally provided in the product information or otherwise given by the manufacturer. There are four main types of pool shock: calcium hypochlorite, sodium hypochlorite, sodium dichloro-s-triazinetrione, and potassium monopersulfate.
- Calcium hypochlorite is the most commonly used pool shock with a typical chlorine level of between 50 to 80 percent. This pool shock is made for quick, potent pool water treatment. After treatment, the heat from the sun turns excess chlorine into a gaseous state, allowing it to escape in the open air.
- Sodium hypochlorite is typically used in liquid pool shock treatments. It has a concentrated formula with an average sodium hypochlorite percentage of 12.5, allowing it to treat up to 20,000 gallons of water per gallon of pool shock treatment.
- Sodium dichloro-s-triazinetrione generally has a lower chlorine level than calcium hypochlorite, at a range of 40 to 50 percent. However, this treatment adds cyanuric acid to the water, which can affect the overall pH balance of the pool, so users need to be careful to balance the chemical composition of the pool water.
- Potassium monopersulfate is a chlorine-free product. It is best for saltwater pools because it helps to remove chloramines, which are formed when chlorine comes into contact with sweat, dirt, oils, and hair. This treatment also reactivates available chlorine molecules in the water, increasing the effect of the saltwater maintenance system. This type of treatment only works if the pool already has a chlorination system; without chlorine present, the potassium monopersulfate is ineffective against microorganisms and other contaminants.
Users who prefer liquid pool shock products needn’t worry about dissolving time, but those using a powder or tablet treatment should keep in mind the time required for the pool shock to dissolve. Most powders will either dissolve within a few minutes of application or may require premixing to prevent the chemicals from damaging vinyl liners.
Tablet pool shock products take 1 to 2 hours to fully dissolve, so there is never enough concentrated shock treatment to damage the pool. However, it isn’t advised to swim while the tablet is dissolving. After shocking the pool, wait for at least 24 hours, then check the pH balance to ensure the water is safe, with a pH between 7 to 7.8, before going for a swim.
A pool’s pH should be checked on a regular basis to ensure the water is safe for swimming. An ideal pH level ranges from a pH of 7 to a pH of 7.8. When the pH levels go above 7.8, the water will be too alkaline (or basic), which can cause red, swollen eyes that are itchy and painful. If the pH falls below 7, the water will be too acidic, which can damage the skin and cause itching, burning, and rashes.
Pool shock is designed for killing bacteria, viruses, plant life, and other microorganisms that may be making their home in the pool. Adding this chemical solution will change the pH level of the pool, so always check the pH after adding pool shock and before entering the pool to make sure the pH level has returned to normal to prevent skin and eye irritation or burning.
Our Top Picks
The list of top products below was selected based on the shopping tips and considerations mentioned above, with significant importance given to product efficacy and overall value. These products are among the best pool shock treatments for your pool.
See results in just 24 hours with this powder pool shock treatment from HTH. It comes with six individual packages that each contain 1 pound of powder pool shock, making it easy to measure out the proper amount for the pool. One package is suitable for treating up to 13,500 gallons of pool water, and the treatment includes a built-in clarifier as well as a helpful color change feature that turns the pool water blue to indicate the pool shock is working.
This calcium hypochlorite pool shock contains 52.5 percent of chlorine, making it a good option for mild to medium pool treatments. The pool shock kills bacteria and algae, prevents scale formation on the sides of the pool and inside the filtration system, and also softens the water. After treatment, the pool should be clean, clear, and ready for swimming within about 24 hours, though users should always check the pH level before jumping in.
No need for a measuring cup here—this powder pool shock treatment is helpfully prepackaged in 24 individual pouches. Each pouch weighs 1 pound and contains enough powder pool shock to treat up to 10,000 gallons of water. The affordable value pack is a great option for those who want to stock up on pool shock and maintenance treatments for an entire season.
A quick-dissolving option, this treatment takes just 30 minutes to disperse. It contains 68 percent calcium hypochlorite, which is used to produce a chlorine concentration of up to 65 percent, helping to kill bacteria, algae, and other organic contaminants that can invade the pool water.
Those who have large in-ground pools would benefit from using this powder pool shock product. Just 1 pound of powder treatment from this 50-pound bucket can treat up to 16,500 gallons of water. There’s no premixing required: Just add the powder directly to the pool water to boost the pool’s chlorine level and destroy waste, algae, bacteria, and other microorganisms.
Thanks to its high calcium hypochlorite concentration of 73 percent, made up of 70 percent available chlorine, this pool shock treatment is a strong option for treating moderate to severe contamination. Although the powder dissolves within 30 minutes, users should scatter the powder around the edges of the pool to prevent clumping on the pool bottom, which could damage the pool liner.
Users looking for a quick, simple solution should consider this Austin’s Pool Tech pool shock product. Instead of premixing powders, placing tablets in chlorinators, or waiting for the pool shock product to dissolve, users will find this liquid option easy to use and suitable for treating between 20,000 gallons and 100,000 gallons of pool water.
For shocking the pool at the beginning or end of the season, the liquid pool shock should be measured out to between 50 to 100 ounces per 10,000 gallons of water. Reduce the amount of pool shock to just 11 ounces per 10,000 gallons for ongoing maintenance. The pool shock treatment contains 12.5 percent sodium hypochlorite, so users can rely on this liquid pool shock for clean, clear water without scale buildup or changes to the level of cyanuric acid in the water.
Tablet pool shock treatments are great for users looking for low-maintenance solutions. By placing a pool shock tablet in the pool’s filter basket or in a chlorinator, the chemicals can be gradually mixed throughout the pool as the tablet dissolves. This slow-release feature ensures the tablet doesn’t damage the pool, with each tablet containing 93.6 percent sodium dichloro-s-triazinetrione, which includes up to 84 percent chlorine.
The 5-pound container includes 12 individual tablets; each tablet is suitable for treating a 10,000-gallon pool of water. Thanks to a sun-protected formula, the treatment will continue working for up to 1 week without evaporating from the heat of a summer day.
Get back to soaking in just 15 minutes with this powder shock treatment from SpaGuard. Specifically designed to be used with hot tubs, this shock treatment comes in a powder that can be poured directly into the spa or hot tub water. It contains 58 percent sodium dichloro-s-triazinetrione, which doesn’t evaporate under the sun, allowing the treatment to continue working for up to 1 week. Apply 1 ounce of spa and hot tub shock treatment for every 500 gallons of water, increasing or decreasing the treatment amount as necessary.
This spa treatment is intended to be a multipurpose maintenance product that can be used to balance or boost the pH of the hot tub water as well as break up any dirt and oil in the tub and kill microorganisms that may thrive in warmer water.
Saltwater pools use salt to produce small amounts of chlorine regularly, so it isn’t often that these pools require high levels of chlorine from calcium hypochlorite products. However, this powder pool shock, from In the Swim, is a chlorine-free option that’s made with potassium monopersulfate, which removes chloramine and reactivates sanitizing chlorine to help eliminate algae and bacteria.
This chlorine-free pool shock comes with 12 individual 1-pound pouches and can be used to treat up to 120,000 gallons of water at a ratio of 1 pound of powder treatment (or one pouch) per 10,000 gallons of water. After application, users only need to wait about 15 minutes before the pool is ready to use again, so a day filled with swimming doesn’t need to be put on hold for regular maintenance.
Tips for Using the Best Pool Shock
Shocking a pool involves raising the pH level rapidly to a point where the solution will kill any microorganisms in the pool. After this initial pool shock, the chlorine level must be maintained weekly, so it’s a good idea to choose a pool shock that’s easy to use. Some users may prefer to scoop a powder, while others will find it easier to work with a liquid pool shock. Choose the format that is most comfortable based on your personal preference. This will help reduce mistakes, spills, and other accidents.
Another great way to avoid accidents, like over chlorinating or under chlorinating, is to follow the manufacturer’s recommendations for use. Keep in mind that a pH level of under 7 can cause sore skin and rashes, while a pH level that exceeds 7.8 can burn swimmers’ eyes.
While chlorine will kill the microorganisms, it doesn’t remove them, so make sure to run the filtration system in order to pull out any dead bugs or plant life. The system will also help to move the shock treatment around, ensuring the effects spread to the entire pool.
- Users should choose a pool shock they are comfortable measuring and applying every week.
- Always refer to the manufacturer’s recommendations for use to avoid over or under chlorinating.
- Run the filtration system to remove dead microorganisms and dirt.
FAQs About Pool Shocks
If you still have questions about pool shock products to get your pool ready for warm weather, such as the difference between chlorine and pool shock or whether liquid or powder pool shock is better, then read on to find the answers to these queries and more.
Q: Should I use liquid or powder pool shock?
Users can choose either liquid or powder pool shock. Both are intended to shock the pool, but some people may prefer the slow disintegration and controlled application of powder pool shock. Though cheaper and quicker, liquid pool shock can splash during the application, burning skin and staining clothing.
Q: Is chlorine the same thing as a pool shock?
Chlorine is the element used to maintain a clean and healthy pool. It only exists in a gaseous state, so it must be mixed into a liquid or a powder. The difference between standard chlorine treatments and a pool shock product is just the dosage of chlorine. Pool shock products are intended to rapidly raise the chlorine level in the water to kill any microorganisms, while standard chlorine treatments have lower doses meant to maintain current chlorine levels.
Q: How do I shock my above-ground pool?
Shocking an above-ground pool follows the same process as shocking an in-ground pool, except that the measurements for the chlorine will be different, based on the amount of water in the pool, the size of the pool, and the manufacturer’s direction.
After reading the directions for use, measure out the required amount of pool shock, pour it into the pool, and leave the pool for the recommended amount of time. Before allowing anyone to enter, test the pH of the pool to make sure it’s within 7 to 7.8, which is ideal for swimming safely.