5 Best Pool Shock Treatments to Clean Your Pool

Updated: May 28, 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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Champion Pool Shock Ready To Use Liquid ChlorineVIA MERCHANT

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.

In The Swim Pool Shock
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Best Overall Pool Shock Treatment

In The Swim Pool Shock


  • Pre-measured doses for easy use
  • Great for quick chlorine boost when fast-action cleaning is needed
  • Granular formula pours directly into pool water
  • Good price to quality ratio


  • Not suitable for vinyl pool liners
  • Not ideal for areas with hard water

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!”

Drytec Calcium Hypochlorite Chlorine Shock
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Best Budget Pool Shock Treatment

DryTec Calcium Hypochlorite Chlorine Shock


  • Budget priced, especially when purchased in bulk
  • Kills bacteria and controls algae
  • Easy to use with no product waste
  • Same chemical make-up as other higher priced products


  • Some users say the product does not dissolve well
  • Not suitable for vinyl pool liners or hard water

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!”

Clorox Pool & Spa Shock For Small Pools
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Best Pool Shock Treatment for Above-Ground Pools

Clorox Pool & Spa Shock for Small Pools


  • Sodium-dichlor formula is easier on pool liners
  • Dissolves right away, so less time out of the pool
  • Smaller portion for small pools
  • Reduces chlorine odor and eye irritation


  • Pricey

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!

Leslie's Fresh 'n Clear Non Chlorine Oxidizing Pool Shock
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Best Chlorine-Free Pool Shock Treatment

Leslie's Fresh 'N Clear Non-Chlorine Oxidizing Pool Shock


  • Chlorine-free oxidizer
  • Works in 15 minutes, so less downtime
  • Compatible with other sanitization methods and chemicals
  • No harsh odor or eye irritation caused by chlorine


  • Not strong enough to tackle tough algae build-up
  • Expensive

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.

Champion Pool Shock Ready To Use Liquid Chlorine
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Best Liquid Pool Shock Treatment

Champion Pool Shock Ready to Use Liquid Chlorine


  • Strong formula with commercial-grade bleach
  • Pours right into the pool water
  • No granules to dissolve
  • Does not cloud pool


  • Liquid chlorine is unstable and will lose potency within 6 months
  • Risk of splashing on skin, eyes or clothing

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.”

What to Consider When Buying Pool Shock

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.

Types of Pool Shock

There are three main types of pool shock:

  • Calcium Hypochlorite (Cal Hypo): This is the most common pool shock and usually the cheapest. Typically sold in granular form, Cal Hypo is a safe bet for most pools. However, it can erode or bleach a vinyl liner, and if you live in an area with hard water, it may lead to increased calcium build-up.
  • Dichlor or Trichlor: Dichlor or trichlor are gentler pool shocks but take longer to dissolve and raise pH levels. They contain cyanuric acid, a stabilizer that extends the life of chlorine but can also raise the pH too high. They’re a good choice for pools in full sun.
  • Potassium Monopersulfate (MPS): The only chlorine-free pool shock option, MPS helps chlorine work more effectively and works to prevent the formation of chloramines. It’s also a fast-acting shock, meaning you can swim within 15 minutes of use. But it’s not a strong enough solution for a pool where algae have gotten out of hand.

Why You Should Trust Us

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.

Nina Derwin is a commerce updates editor for Reader’s Digest, Taste of Home and Family Handyman and has experience researching and reviewing various items to help shoppers find the best products on the market. She researched and updated this piece.

How We Found the Best Pool Shock

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.


Are pool shock and chlorine the same thing?

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.

Should I add shock or chlorine first?

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.

When should you shock your pool?

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.