Best Pool Shock: Review & Buying Guide for Pool Owners

There’s nothing worse than coming home from a vacation or getting a little busy at work, only to see your pool has turned a delightful shade of green. Especially if you’ve been craving a swim.

But I’ve good news for you, even if you’ve been a little less than diligent in your pool maintenance. There’s a simple solution to get your pool crystal clear again. Pool shock.

It’s the smoking gun in your battle against an algae-infested pool. Turning the tables even if you’ve been neglecting your pool maintenance duties.

Pool shock will help you bring your water back from the brink, and in this guide let me run you through the best pool shock on the market.

Top Picks for Pool Shock

We hand-picked the following pool shock products based on their popularity, price-points and differentiating features.

A more complete review of each can be found later in this article.

What is Pool Shock?

Pool shock is your solution to get a neglected swimming pool safe for swimming. It’s essentially a massive injection of chemicals to destroy harmful bacteria, algae, and any other contaminants.

It works by spiking the chlorine levels (often up to 5 times normal levels), to sanitize the water, while also oxidizing combined chlorine molecules. This boosts your free chlorine levels, which is the “good” chlorine you want. It targets and kills bacteria and algae.

Some pool owners like to regularly shock their pools every few weeks, especially during heavy use or if there have been contamination events, like heavy rainfall or storms. This helps disinfect a pool, ensuring it stays crystal clear and ready for swimming.

If you notice a heavy chlorine smell, your pool is looking a little less clear than usual, or you’re planning to start-up (or close-down) your pool for winter, it’s a good idea to use pool shock to get the water back in balance.

What Types of Pool Shock Can You Buy?

Swimming pool shock comes in a variety of forms, each with their own unique features, build quality and wildly different price-points to boot.

In this section, I’ll cover the different types you can buy for your pool as well as the benefits and drawbacks of each.

Calcium Hypochlorite

Calcium hypochlorite is often referred to as “cal hypo” and is one of the most economical pool shocks you can buy. Available in 65% and 73% strengths, it’s not stabilized, which means it’s best used in the evening when the sun won’t speed up the chlorine breakdown.

As one of the strongest pool shocks available, care needs to be taken to avoid any damage to your pool liner as the undissolved powder will bleach the liner.

Most pool owners will pre-mix cal hypo in a separate bucket of water (remember, always add the chemicals to the water, not the other way around), to get it properly dissolved before it’s tipped into the deep end of a pool.

The downside to this powder is it will raise the pH level of your water, while also increasing the calcium levels in your pool. Once the chlorine levels return to normal, it’s safe again for swimming, though this may take up to 8 hours.

Sodium Di-Chlor

Sodium dichloro-s-triazinetrione is often referred to as just “dichlor” and is a stabilized pool shock you can safely use at any time of the day. Available in a 56% strength, it won’t add calcium to the pool, though it may boost your cyanuric acid levels (the stabilizing agent).

This pool shock is particularly useful if you want to maintain higher chlorine levels for an extended period, to thoroughly disinfect against chlorine-resistant parasites and bacteria that may be present in your pool.

Slightly more expensive than cal hypo, the critical benefit of this pool shock is that it has a nearly neutral pH level, and typically it’s safe to swim in your pool within 15 to 30 minutes.

Potassium Mono Persulfate

Potassium Mono Persulfate is often referred to as a non-chlorine shock as it is a little different to the other types of pool shock available. The difference being, it doesn’t contain chlorine.

Ideal for use in pools which use bromine as the sanitizer, this type of shock is just as effective in chlorine-based pools as well. Unaffected by sunlight, the non-chlorine shock works by oxidizing your pool water to boost the levels of “free” chlorine available.

Because it doesn’t contain high levels of chlorine like other shocks it’s a little safer, but it is an expensive option if you’re using it as part of your regular pool maintenance.

The good thing about a lack of chlorine is that it won’t bleach your pool liner, and it also doesn’t give off a strong odor, great if you’re using this to shock an indoor pool. Plus, it’s dissolved fast, you can start swimming again just 15 minutes after adding it to your water.

But Which Type of Pool Shock Is Best?

When it all comes down to it, the right type of pool shock will be based on what you’re looking to achieve.

If you’re just wanting to fight off algae, a cal hypo shock is an economical choice that will get the job done. If you’re wanting to sanitize a pool that uses bromine as one of the key chemicals, you need a non-chlorine shock.

And if you want to start shocking your pool regularly, all three are viable options – so long as you’re actively testing and monitoring the chemical balance in your pool.

What Should You Look for When Buying Pool Shock?

Knowing which type to look for will narrow down your options, but it doesn’t help you measure the nuances that make or break a product.

Let’s go over some of the main criteria you should apply to your decision making process when looking for the perfect pool shock for your swimming pool.

Dissolve Speed

Before the shock can be added to your swimming pool, it needs to be dissolved. Most pool owners do this in a separate 5-gallon bucket before they pour the shock into their pool.

If it hasn’t properly dissolved, the powdered shock granules can bleach your pool liner.

Of course, dissolve speed plays an important role here. The faster the granules dissolve, the quicker you’ll be able to add your pool shock to the water, making it a more efficient process. A fast dissolve speed makes it less likely you’ll add the un-dissolved powder to your pool.

Chlorine Level

The overall goal of pool shock is to send your chlorine levels through the roof (temporarily at least), as helps to keep your swimming pool water sanitary.

Before you buy any pool shock product, make sure to check the available chlorine percentage, and pay attention to whether it is stabilized or not.  

Many pool shocks (like the cal hypo types especially) are not stabilized, which means they can only be effectively used once the sun goes down. An “overnight” treatment, to avoid the UV rays that speed up the breakdown process of the chlorine.

I should note here, that one of the pool shocks we recommend is a non-chlorine shock, but it has the same end result, oxidizing your water to rapidly boost free chlorine levels.  

pH Level (Neutral)

Keeping your swimming pool water in balance also requires a stable pH level, and even small changes in this can make a big difference.

When pH levels drop too low, the pool water becomes corrosive and will damage all of your piping, any metal components, and anything that gets left in the water too long.

When pH levels get too high, the acidity of the water will become an irritant, hurting the eyes, ears, nose, and mouth of anyone who uses your pool.

Look for a pool shock that will not have an impact on your pH levels, and if that’s not an option, make sure you’re adequately testing the water and have solutions on hand to bring the pH back into balance once the shock is done.

Free of Additives

Ultimately, you want your pool shock to have as little impact on your pool water as possible.

Trouble is, lots of products have additional compounds and chemicals to help them to work, and if you’re needing to shock your pool regularly these additives add up fast.

In general, you can expect cal hypo pool shocks to raise your calcium levels, while dichlor will result in the addition of cyanuric acid to your water.

It’s not possible to get a pool shock completely additive free, but it’s recommended you look to the simpler options so as not to fill your pool with a bunch of unnecessary chemicals.

Powdered vs. Liquid

Most pool shocks are offered in powdered form, which requires just a little effort to pre-mix it before you tip it into your pool.

A liquid pool shock is an excellent option if you’re looking for convenience because it’s already fully dissolved it won’t bleach your pool liner. You can just tip it straight in. The downside is it is more expensive than the powdered option.

Reviewing the 7 Best Pool Shock Products

So far we’ve covered what pool shock is, why you need it, the different types available, and what features to look out for.

In this section, we’ll be looking at specific products, each of which were hand-picked for review based on the same criteria I’ve outlined in this guide.

Let’s dive right in. (See what I did there, huh?)

#1. Clorox Pool&Spa Shock Plus

Designed by Clorox, Pool&Spa Shock Plus is a powerful pool shock that is specifically focused on removing swimmer contaminants and improvingfilter performance. Its 4-in-1 formula won’t impact the pH of your pool – leaving it clean, clear and safe to swim.

One of the best features is its easy open, easy pour bottle, each containing 1-pound, 6-pounds, or even 12-pounds of pool shock.

This pool shock has a neutral pH so it won’t affect the water balance in your pool, and Clorox also mentions that it will not bleach your liner. Many users say it’s just as good as the expensive brands, although some shoppers received a product past its expiration date.

Pros:

• The bottle is easy to open and use, giving more control over the chemicals
• The granulated shock allows the pool owner to broadcast it into the middle pool area for better coverage
• Water will be safe for swimming within just 15 minutes of treatment

Cons:

• Keep an eye on the expiration date as older chemicals don’t work

#2. Aqua Chem Shock Xtra Blue

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Designed by Aqua Chem, the Shock Xtra Blue is a similar choice to Clorox’s option, although this one comes in a bag instead of a bottle, also separated in 1-pound amounts.

You’ve got the choice to buy in quantities from 1 to 36 bags, ensuring you’ve got plenty of shock to last you all summer long, and keep your pool sparkling. Using an active ingredient of sodium dichloro-s-triazinetrione, this pool shock provides 39% available chlorine.

One of the most significant benefits is that it will not raise your pH levels while it is fighting to clear up your cloudy water, the added algaecide will help sanitize any nasty infestations in your swimming pool. A few buyers have raised concerns at just how well this pool shock works, along with its tendency to stain your filter cartridges.

Pros:

• Separated into 1-pound bags for easy use (and little mess)
• Water will be safe for swimming within just 15 minutes of treatment

Cons:

• Expensive compared to other pool shock options

#3. hth Super Shock Treatment

Designed by hth, the Super Shock treatment is a fast-acting solution to improve the quality of the water in your swimming pool.

With a promise of crystal-clear water in 24 hours, this treatment uses an active ingredient of calcium hypochlorite, providing 54% available chlorine.  

Available in convenient to use in 1-pound bags, the manufacturer states this shock won’t discolor your liner, though it can take time to dissolve properly in your swimming pool.

Expensive if you’re not buying in bulk, the downside with this shock treatment is that it takes time to work (often several hours), and needs to be done overnight.

Pros:

• Suitable for use in salt water swimming pools

Cons:

• Expensive treatment option if you’re not buying in bulk
• Water will only be safe for swimming after several hours

#4. DryTec Chlorinating Shock Treatment

Designed by DryTec, this pool shock treatment is a much coarser grain than other options, which does have an impact on how soluble it is in the water.

With an active ingredient of calcium hypochlorite, it provides 65% available chlorine, one of the highest in all of the pool shocks in this list. Plus, it comes in individual 1-pound bags which are very convenient to use.

What I like best is that there are no additives to throw the balance of your pool, while being a potent and fast-acting option to kill bacteria and bring algae under control. The downside is that it doesn’t dissolve very well, and being unstabilized you’ll have to shock your pool overnight.

Pros:

• High chlorine level to fix any problems in your pool water

Cons:

• Water will only be safe for swimming after several hours

#5. Pool Essentials Shock Treatment

Designed by Pool Essentials, this is a shock treatment for all types of swimming pools, whether you’re feeding it through the skimmer or pouring into the deep end of the pool.

It has an active ingredient of trichloro-s-triazinetrione which essentially classifies it under the dichloro banner, giving you 48.6% available chlorine in each 1-pound bag,

Despite being much larger granules, this pool shock is still quite soluble in the water for the size, a nice benefit to ensure you don’t get a face full of chlorine dust when you open each individual pack.

The downside is the stabilizer. Many buyers saw their cyanuric acid levels skyrocket after using this pool shock, which isn’t ideal, especially if you’re using it once a week as the manufacturer recommends.

Pros:

• Safe to use in both in-ground and above-ground swimming pools

Cons:

• Can bleach vinyl pool lining if not properly dissolved
• High levels of cyanuric acid (stabilizer) will affect your pool composition

#6. Zappit 73% Cal Hypo Pool Shock

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Designed by Zappit, this is one of the most potent pool shocks you will find.

Not only is it incredibly economical, but you also get a shock providing 70% available chlorine (from an active ingredient of calcium hypochlorite).

Trouble is, it comes in a massive, 50-pound bucket. You’ll have more than enough to last through the summer, keeping your pool perfectly in balance, but it’s not that user-friendly.

The lid is prone to breaking, and you’ll spend the first 10 minutes digging around looking for the measuring cup that’s buried somewhere in the bucket. Oh, and it can also result in calcium silt on the bottom of your pool, which you’ll need to vacuum out as it settles.

Pros:

• One of the strongest pool shock products on the market

Cons:

• Large buckets can be challenging to open and cumbersome to use
• Can create calcium silt which needs to be vacuumed out

#7. In The Swim Chlorine-Free Pool Shock

Designed by In The Swim, what’s novel about this pool shock is that it is chlorine-free.

Packed in convenient 1-pound bags, this pool shock uses an active ingredient of potassium monopersulfate. There’s no available chlorine. What it does though, is starting an oxidization process in your pool, that burns off dead chlorine cells.

As your free chlorine levels rise in the water, they become more effective at battling bacteria, algae and any other nasties in your swimming pool. If you’re using bromine to sanitize your pool, this is the stabilizer for you.

What I love best is it won’t throw your pH levels out of balance, and it’ll be safe for swimming within just 15 minutes. The downside is that it’s really only best for maintenance, if you’re looking for a solid “shock” to fight off a significant algae bloom, this is probably not the most effective choice.

Pros:

• Can tip straight into your swimming pool with no need to pre-mix
• Chemicals aren’t as harsh as other shocks and won’t bleach your pool liner

Cons:

• Not impressive results against a big problem in your swimming pool

Our Winners

Overall, the DryTech treatment option is our recommendation for the best pool shock. High available chlorine provides a better sanitization, while the smaller use bags make it easy and convenient to use.

But the best part is the lack of cyanuric acid so you won’t have to worry about sending your pool’s chemistry all out of whack if you’re using this shock treatment.

The Runner Up:

The Zappit 73% pool shock is just so damn effective, and the chlorine boost you get is second to none. Where it loses out is the ease of use. Large buckets make it unwieldy to carry around, and the locking mechanism on the lid is far too flimsy. But if you’re looking for a cheap and effective pool shocker, that’s precisely what you get.

When your swimming pool is looking a little worse for wear, a pool shock treatment can bring it back to normal. Fighting off the growth of bacteria and algae, the chlorine boost will help prevent their return so you can enjoy a nice, pleasant swim.

That’s why you got the pool in the first place, right?

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