Updated on Oct. 15, 2024
This may come as a shock, but not all pool shock treatments are the same. Here's a look at the best pool shock products for your swimming pool.
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With summer in full swing, your backyard swimming pool—whether an in-ground or above-ground —is likely getting a lot of use. And with all that activity comes additional maintenance, from regularly running the pool vacuum to washing or changing pool filters. Warmer water temperatures, sunscreen-covered kids and adults in and out of the pool, and rainstorms can increase the pH of your pool, making your chlorine less effective. Periodic shocking of the pool, especially during busy summer months, is an essential maintenance task for most pools and helps keep them clean, clear and sanitized.
“Shocking” a pool is just adding a large dose of chemicals, usually chlorine, to the water to quickly rebalance and adjust chlorine levels in the water, keeping the water clear and algae-free. Swimming pools need to be shocked during periods of high use and before winterization.
Not all pool shock products are the same, though, and one type or another may or may not be best suited to your swimming pool. So to help you choose the best shock for your pool, we’ve rounded up the top options in several different categories.
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We like this highly-rated and easy-to-use pool shock for several reasons. One, In The Swim Pool Shock is composed of calcium-hypochlorite (cal-hypo in industry lingo), so it’s a great start-up shock if you’re just opening your pool for the season. Two, it contains a high percentage of active chlorine that will zap bacteria and algae and quickly clear up pool water. And three, it’s sold in multi-packs of 1-pound doses, and a single pack is enough for 10,000 gallons of pool water.
Amazon purchaser Olga Salnikova calls it a miracle product. “I was skeptical because nothing seems to work in our above ground pool due to pump possibly been a little smaller than needed. I used tons of pool bleach and still pool would turn green,” they say. “Decided to give this a try and it’s crystal clear! I use it at night and leave the pump running. From green to clean!”
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A bulk purchase of 1-pound packets of this cal-hypo will save you big bucks! Like other cal-hypo formulas, DryTec Calcium Hypochlorite Chlorine Shock is a fast-acting shock that will eliminate algae, bacteria and organic contaminants.
The granular formula can be poured right into the pool, though some reviewers, like Amazon purchaser Wally Wagner, recommend concentrating it around areas with algae growth: ” I sprinkled several packets around the areas where there were algae stains letting much of the compound settle to the bottom. After a few minutes I lightly brushed the granules that settled to the bottom to mix them into the water a little so they wouldn’t create some new stains. Amazingly I noticed all of my algae stains were already gone!”
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If you have an above-ground pool, chances are it has smaller dimensions than typical in-ground pools. That means you need smaller doses of pool shock. We like that this granule formula comes in a resealable bottle, so you can measure the precise amount you need. It’s a sodium-dichlor product, which means it’s suitable for all pool materials. It also dissipates right away, which means your crew can get back in the water sooner.
Clorox Pool & Spa Shock is fast-dissolving and creates crystal-clear water in just 15 minutes. It is best for use in smaller pools (up to 5,000 gallons) and reduces chlorine odor and eye irritation for a more pleasant swim experience. Plus, the shock bottle is resealable and recyclable, unlike other traditional pool shock bags!
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Leslie’s Pool Supply suggests this product as an alternative to harsh chlorine shocks that can make it harder for chlorine to do its job. This chlorine-free formula uses potassium peroxymonosulfate (MPS) as the active ingredient. MSP helps prevent the formation of chloramines, which are chlorine bound with non-living organic contaminants, preventing chlorine from effectively sanitizing.
Leslie’s Fresh ‘N Clear Non-Chlorine Pool Shock is a periodic shock that can be used with chlorine, bromine or saltwater systems and is safe for vinyl liners. Several purchasers claim the product cleared up green or murky water right away and reduced the amount of chlorine they add to their pool water.
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This strong formula uses 12.5% sodium hypochlorite, or liquid bleach, as its active shock ingredient. Since it’s in liquid form, you add it directly to your pool without waiting for granules to dissolve.
Champion Liquid Pool Shock is a quick, powerful fix for algae and bacteria and is safe for vinyl liners and saltwater pools. It also has other uses, such as a cleaning solution (when diluted) for pressure washing. Verified Amazon purchaser Barry Harrell says it’s the best treatment for “when the pool gets out of hand” and loves that “the price is right and it works really well.”
Shocking a pool is a standard part of pool ownership and maintenance. When choosing a pool shock product, pay attention to the product’s compatibility with your type of pool. Vinyl liners, in particular, are vulnerable to damage from shock granules that may accumulate on the bottom of the pool.
Every pool’s chemical balance is different, and it may take a few test runs with different formulas to determine the best pool shock for your pool. While pool maintenance is a perfectly reasonably DIY task, we recommend that you periodically take a sample of your pool water to your local pool supply store, especially if you’re having difficulty getting pH and total alkalinity numbers where they should be. At the supply store, they’ll analyze your water sample, diagnose any issues and recommend products to remediate any problems.
There are three main types of pool shock:
Nearly all shock treatments offer a specific amount of free chlorine on the package.e It tells you how much is needed to eliminate the waste in the pool, which, in turn, keeps your pool clean. These shock treatments are part of a healthy pool route and offer around 55 percent free chlorine, while stronger treats contain around 70 percent.
Pool conditions change the stability of its water. From the amount of sunlight to the age of your pool, these facts will determine ifit’s suitable or not. And if you have an above-ground pool, the vinyl liner can break down faster. These factors will decide whether or not you need to opt for a stabilized, unstabilized, or chlorine-free option. If you choose unstabilized chlorine, note that it does not include cyanuric acid (CYA), whereas stabilized chlorine does. If your pool measurements reveal that your pool has elevated CYA levels, choose an unstabilized shock.
Shocking your pool serves multiple functions that include:
Don’t worry! Chlorine and chlorine-free shocks are safe for swimmers and pets. To ensure that the pool remains safe while shocking, follow all of the instructions from start to finish. Also, remember that you should never mix different shocks or chemical treatments and should always start the water before anyone takes a dip.
Elizabeth Heath, the author of this piece, is an experienced home improvement writer. Her work has been featured in publications including The Washington Post, Travel + Leisure, Reader’s Digest, Family Handyman and TripSavvy. She has also published several guidebooks and completed countless home improvement projects.
Pool shock is an important element of pool maintenance, and choosing the right product is key. To find the best pool shocks on the market, we first considered the different types of products and their effectiveness in keeping your pool clean and free of algae and other bacteria. We researched different options, weighing price, ease of use, and how much, if any, eye irritation occurs after use. We carefully considered customer reviews and chose the products that balance high efficacy with affordability and dissolve time.
Manufacturers recommend one pound of pool shock per 10,000 gallons of water. Some shocks are sold in bulk, while others are available in smaller quantities.
Nearly all pools work with pool shock, but to help, here’s a quick list:
The most common types of pool shock, cal hypo, dichlor and trichlor, all contain concentrated doses of chlorine. Only MPS is chlorine-free. But household bleach, for example, is not a substitute for pool shock, as it’s a much more diluted form of chlorine.
Shock is a periodic, as-needed treatment, while chlorine is a regular part of pool maintenance. Shocking the pool allows you to reset chlorine levels quickly. After a shock, you can resume normal chlorine application.
Unless you use a fast-acting shock treatment, shocking your pool means time spent out of the water while the chemicals disperse. For that reason, most pool owners shock their pools in the evening and let the pump run overnight so they can jump back into the (newly clean and clear) water the next day.
