Published on July 21st, 2020 | by Roger Corbinetti0
Best Pool Shock of 2020 – Reviews, Top Picks & Buyer’s Guide
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Shopping for the right pool shock for your swimming pool?
You’ve come to the right place.
Pool shock is the most effective way of dealing with bacteria, algae, and other contaminants in a swimming pool.
Pool shock can be added to the pool regularly or for a particular reason such as an algae bloom, after a heavy rainstorm or after heavy use.
Whats in This Guide
- Whats in This Guide
- What Is Pool Shock and What Are the Types Available?
- The 8 Best Pool Shocks Reviewed
- 1. Best for All Pool Types: Aqua-Chem Xtra Blue Pool Shock
- 2. Best for Vinyl Pools: Clorox Pool & Spa Shock Plus
- 3. Best Value for Money: HTH Pool Super Shock
- 4. Best for Cloudy Water Treatment: Pool Essentials Shock Treatment
- 5. Best Non-Chlorine Shock: Leisure Time RENU2 Pool Shock
- 6. Best for Spas and Hot Tubs: SpaGuard Enhanced Shock
- 7. Best for Quick Sanitizing: DryTec Calcium Hypochlorite Shock
- 8. Best for Regular Maintenance: In The Swim Chlorine Pool Shock
- How To Choose The Right Shock For Your Pool
- How to Shock Your Pool?
- Frequently Asked Questions
What Is Pool Shock and What Are the Types Available?
Pool shock is a chemical oxidizer that breaks down organic contaminants in the pool and oxidizes combined chlorines or chloramines. Chloramines give your pool a strong chlorine smell and cause eye irritation when you swim in the pool.
Pool shock, specifically calcium hypochlorite, is also used as an algaecide to kill algae in the pool. It also kills bacteria.
Essentially, pool shock is a powerful pool cleaner that’s used when the pool has higher than average levels of contaminants or too little free chlorine.
There are three types of pool shock. Each is ideal for a different kind of pool and situation.
Cal Hypo, as it’s also called, is the most commonly used type of pool shock. You’ll find it in different strengths ranging from 50% to around 70% chlorine.
Calcium Hypochlorite is highly effective against chloramines, organic contaminants, bacteria, and algae. It’s the cheapest type of pool shock.
On the downside, calcium hypochlorite is harsh on pool surfaces, particularly vinyl. That’s why it’s a good idea to pre-dissolve the shock in a bucket before you add it to the pool. You also cannot swim immediately after adding it. You have to wait 24-48 hours for chlorine levels to come down to a safe level.
Also, calcium hypochlorite adds calcium to the pool. This is a problem if you already have hard water.
Sodium dichlor is stabilized pool shock. It has cyanuric acid added to it to prevent UV degradation. Dichlor is pH-neutral thus won’t raise your pool pH levels.
Like Cal hypo, Dichlor oxidizes chloramines as well as organic contaminants. It’s an effective way to purify the pool after a storm or heavy use. Dichlor also kills bacteria and algae.
Because Dichlor doesn’t add calcium to the water, it’s perfect for pool owners that struggle with hard water.
Like Cal Hypo, Dichlor is harsh and can bleach pool surfaces, especially vinyl. You also have to pre-dissolve it and wait 24-48 hours before using the pool.
Another downside of Dichlor is that it adds cyanuric acid to water. But this is only an issue if your pool already has high levels of cyanuric acid.
Do a quick pool test before you settle on a pool shock. If there are high levels of cyanuric acid, opt for calcium hypochlorite or non-chlorine shock instead.
Potassium monopersulfate or non-chlorine shock uses a chlorine-free formula to oxidize organic impurities and remove chloramines.
Non-chlorine shock is less harsh than the other two types of chlorine shock, making it ideal for vinyl pools. Also, you can use the pool immediately after shocking it.
Another advantage of non-chlorine shock is that it also doesn’t add calcium or cyanuric acid to the water.
On the downside, Potassium Monopersulfate is not very effective against algae and bacteria.
The 8 Best Pool Shocks Reviewed
- Best for all pool types: Aqua-Chem Xtra Blue
- Best for vinyl pools: Clorox Pool & Spa Shock Plus
- Best value for money: HTH Pool Shock Super Shock
- Best for cloudy water treatment: Pool Essentials Shock Treatment
- Best non-chlorine shock: Leisure Time RENU2 Pool Shock
- Best for Spas and Hot Tubs: SpaGuard Enhanced Shock
- Best for quick sanitizing: DryTec Calcium Hypochlorite Shock
- Best for regular maintenance: In The Swim Chlorine Pool Shock
|Pool shock||Best for||Type||Available chlorine||Kills||Dosage||pH neutral|
|Aqua Chem Xtra Blue||Best for all pool types||Chlorine shock||39%||Bacteria & algae||1lb for 12,000 gal||Yes|
|Clorox Pool & Spa Shock Plus||Best for vinyl pools||Dichlor chlorine shock||37%||Bacteria & only mild levels of algae||1lb for 12,000 gal||Yes|
|HTH Super Shock||Best value for money||Calcium hypochlorite shock||54%||Bacteria & algae||1lb for 10,000 gal||No|
|Pool Essentials||Best for cloudy water treatment||Chlorine shock||40%||Bacteria & algae||1lb for 10,000 gal||No|
|Leisure Time RENU2 ||Best non-chlorine shock||Non-chlorine shock||None||Some bacteria, no algae||4oz for 250 gal||Yes|
|SpaGuard Enhanced Shock||Best for spas and hot tubs||Dichlor chlorine shock||58.2%||Bacteria & only mild levels of algae||3 tablespoons for 500 gal||No|
|DryTec Calcium Hypochlorite||Best for quick sanitizing||Calcium hypochlorite shock||68%||Bacteria & algae||1lb for 10,000 gal||No|
|In The Swim||Best for regular maintenance||Calcium hypochlorite shock||65%||Bacteria & algae||1lb for 10,000 gal||No|
1. Best for All Pool Types: Aqua-Chem Xtra Blue Pool Shock
Aqua-Chem Xtra Blue is chlorine-based, but it’s formulated differently from other chlorine pool shocks. It kills bacteria and algae while being gentle on your pool liner. You can swim just 15 minutes after the application.
- Gentle on pool surfaces.
- Doesn’t increase water pH.
- Kills bacteria and algae.
- Breaks down chloramines.
- Safe for all types of pools.
- More expensive than ordinary pool shock.
Ordinary chlorine pool shocks have at least 65% chlorine. They are effective on bacteria and algae, but harsh on your pool and you have to wait a day or two before getting into the pool.
Aqua-Chem Xtra Blue uses less chlorine (39%) but works just as well at clearing up your pool. It contains added ingredients, including copper algaecide, that allows it to tackle bacteria and algae without bleaching your pool liner.
Aqua-Chem Xtra Blue also breaks down chloramines, which reduces eye irritation and chlorine odor. It also oxidizes organic contaminants introduced by rain, dirt, or people.
Because of its gentle formulation, you don’t need to pre-dissolve Xtra Blue before adding it to the pool. Pour it indirectly. A 1-lb bag is good for 12,000 gallons.
The manufacturer says you can swim in the pool 15 minutes after adding the shock.
However, if you have a lot of algae or cloudiness in your pool, you may need to use more than the recommended amount of Aqua-Chem Xtra Blue shock. In that case, it’s a good idea to wait longer before jumping into the pool.
Tip: Always do a quick chlorine test before using the pool. Only get in the pool if free chlorine is between 1ppm and 4ppm.
Note that Aqua-Chem Xtra Blue is pH neutral. It will not affect the pH level of your pool.
Issues & Concerns
Aqua-Chem Xtra Blue costs significantly more than ordinary chlorine pool shock. If you are looking for a budget pool shock, this is not it.
Though pricey, the Aqua-Chem Xtra Blue pool shock is the best choice for pool owners looking for an effective and fast-working chlorine pool shock that’s pH neutral and safe for their pool surface.
2. Best for Vinyl Pools: Clorox Pool & Spa Shock Plus
If you have a vinyl pool, be careful when shocking it. Strong chlorine shocks can bleach the liner and make it brittle.
To be safe, we recommend a pool shock with a gentler formulation like the Clorox Pool & Spa Shock Plus.
Clorox is pH neutral and is gentle enough that you can pour it directly into the pool without dissolving it.
- Gentle on vinyl pools.
- Kills bacteria and some algae.
- Breaks down chloramines and organic contaminants.
- It contains cyanuric to stabilize free chlorine.
- 15-minute swimming wait time.
- Not effective for pools with high levels of algae.
Similar to Aqua-Chem, Clorox contains less chlorine than ordinary pool shock – 37% to be specific. This makes it a gentle choice for vinyl pools.
There is very little risk of bleaching and damaging your pool liner. You can add the Clorox shock directly to the pool without dissolving it in a bucket. But make sure you brush the pool after a few minutes to dissolve any granules that have settled at the bottom.
Clorox is effective against all the usual unwanted stuff in your pool: bacteria, organic impurities, cloudiness, chloramines, ammonia, and algae.
While Clorox does kill algae, we do not recommend using it as an algaecide. It works great for small amounts of algae and preventing algae growth, but if your pool has lots of algae, first use an algaecide or a strong pool shock to get rid of it.
Afterward, you can add Clorox regularly (the manufacturer recommends weekly) to keep algae from recurring.
Clorox Pool & Spa Shock Plus is a dichlor pool shock, meaning it contains cyanuric acid to stabilize the free chlorine. This prevents sunlight from degrading the pool shock and maintains chlorine at the right level to keep the pool clean and sanitary.
Clorox is pH neutral, so it will not affect your pool’s pH. It also doesn’t add calcium to the pool.
A 1-lb bag of Clorox is good for 12,000 gallons. After application, wait 15 minutes or until chlorine levels are between 1ppm and 4ppm to get into the pool.
Issues & Concerns
The main limitation of the Clorox Pool & Spa Shock Plus is its reduced effectiveness against high levels of algae. If your pool has a lot of algae, first use an algaecide or a strong pool shock.
With the Clorox Pool & Spa Shock Plus, you can keep your pool clean and algae-free without worrying about damaging the vinyl liner.
3. Best Value for Money: HTH Pool Super Shock
If you are on a budget, calcium hypochlorite pool shock is the cheapest option you’ll find. It can be a bit harsh on some pools, but it’s highly effective against bacteria and algae.
The HTH Pool super shock leaves your pool crystal clear. It’s perfect for clearing up large amounts of algae, water cloudiness, and chlorine smell.
- Very effective against bacteria and algae.
- Great price.
- Less harsh compared to most calcium hypochlorite shocks and super shocks.
- No pre-dissolving needed.
- Higher risk of the bleaching pool liner.
HTH contains 54% free chlorine. That’s much higher than both Clorox and Aqua-Chem. The higher chlorine content allows HTH to tackle bacteria and algae quickly and effectively.
HTH is especially ideal if you are struggling with high levels of algae or cloudiness in your swimming pool. It also gets rid of the strong chlorine and eye irritation caused by chloramines.
Besides, HTH oxidizes organic impurities left behind after heavy use. After a weekend of family swimming or a party, use HTH super shock to get sanitize the pool.
The higher chlorine content of HTH also makes it an effective way to quickly raise chlorine levels if you discover they are very low (such as after a period of strong sunshine).
The 54% chlorine level is below what you’ll find in most Cal Hypo pool shocks. So HTH is gentler on your pool liner. The manufacturer says you can pour the granules directly into the water (a 1-lb bag is good for 10,000 gallons) instead of pre-dissolving it.
But if you have a vinyl liner, you may want to pre-dissolve it just to be safe. Alternatively, brush the pool after you add the shock to dissolve any granules that settle at the bottom.
Issues & Concerns
The manufacturer says HTH is safe for most pools, and no pre-dissolving is needed. But if you have a vinyl pool, be careful as there’s a high risk of bleaching and damaging the liner.
Either pre-dissolve the shock or brush immediately after application to dissolve any remaining granules.
HTH pool super shock is a great choice for pool owners looking for a low-price pool shock that works quickly and effectively.
4. Best for Cloudy Water Treatment: Pool Essentials Shock Treatment
If you are struggling with cloudy pool water, the Pool Essential Shock Treatment is the best solution. But first, make sure the cloudiness is not caused by too much chlorine or improper pH levels.
Pool Essentials only helps if the cloudiness is caused by debris and other impurities.
- Clears cloudy water fast.
- Reduces chlorine smell and eye irritation.
- Save for vinyl-lined pools.
- Kills bacteria.
- Smaller than average bags (13oz instead of the usual 1lb).
The Pool Essentials shock treatment has 40% chlorine. So don’t expect it to clear a huge algae infestation in your pool.
It’s best for clearing up a cloudy pool, reducing chlorine odor, and sanitizing the water.
You can add Pool Essentials directly to the pool (even if you have a vinyl pool). It dissolves fast and, unlike most shock, doesn’t leave granules at the bottom of the pool.
After adding the shock, it should take less than an hour for chlorine levels to go back down to safe levels. Make sure you test before getting into the pool.
Issues & Concerns
The main complaint from pool owners is the size of individual bags. Pool shock comes standard in a 1 pound bag that you use in one go. In contrast, Pool Essentials comes in smaller 13.4oz bags that make it harder to measure the amount you need to add to the pool.
Pool Essentials Shock Treatment is the best way to deal with a cloudy pool without damaging the liner. It’ll also kill bacteria, prevent algae growth, and get rid of the unpleasant chlorine smell.
5. Best Non-Chlorine Shock: Leisure Time RENU2 Pool Shock
Leisure Time RENU2Â is the best non-chlorine pool shock. It oxidizes organic contaminants such as oils, sweat, and dead skin cells and removes chloramines.
Because non-chlorine shock is not as effective as chlorine shock against bacteria and algae, make sure you maintain your pool’s chlorine levels to keep it sanitized.
Because of its small size, the Leisure Time RENU2 is mostly ideal for spas, hot tubs, and small above ground pools. You can still use it in a standard size pool, but you’ll need a lot of it, and it’s pricey.
- Oxidizes organic contaminants to improve pool clarity and sanitation.
- Removes chlorine odor and prevents eye irritation.
- Doesn’t affect water pH.
- Doesn’t add cyanuric acid or calcium to the water.
- You can swim immediately after adding the shock.
- Doesn’t kill algae.
- Expensive, making it ideal for small pools only.
The best use of the Leisure Time RENU2 non-chlorine pool shocks are oxidizing organic contaminants introduced by dust, bird droppings, bugs, and other impurities. It also eliminates organic components introduced by swimmers, including sweat, oils, and deodorant.
Leisure Time RENU2Â is also a great way to eliminate chloramines in the water, along with the smell and eye irritation they cause.
The RENU2 can also kill some bacteria, but we do not recommend relying on it for your pool sanitation. It’s not as effective as chlorine shock at killing bacteria.
So make sure you maintain your pool’s chlorine levels.
Leisure Time RENU2Â comes in a 2.2lb bottle with a recommended dosage of 4oz for every 250 gallons of water.
Because you’d need a lot of it to shock a standard size pool, we recommend it for small above ground pools, spas, and hot tubs.
Issues & Concerns
Leisure Time RENU2 does not kill algae. If you have an algae problem in your pool, you’ll have to get an algaecide or a chlorine shock.
Also, Leisure Time RENU2Â is not as effective against bacteria as chlorine shock.
Leisure Time RENU2Â is a great choice if you are looking for a non-chlorine shock for your small above ground pool, spa, or hot tub.
6. Best for Spas and Hot Tubs: SpaGuard Enhanced Shock
If you prefer chlorinated shock for your spa or hot tub, we recommend the SpaGuard Enhanced Shock. The sodium dichlor formulation provides both oxidation (for removing chloramines and organic impurities) and sanitation (for bacteria).
You can also use SpaGuard for a swimming pool, but it’ll be very expensive since you’ll need multiple bottles.
- Chlorinated shock – oxidizes and sanitizes.
- Safe for both chlorine and bromine spas and hot tubs.
- Tub/spa ready to use after 15 minutes.
- 4-in-1 function: shock, clarifier, flocculent, and pH buffer.
- Not ideal for pools.
The advantage of using a chorine shock in a spa or hot tub is that you accomplish two things at once: oxidation and sanitation.
SpaGuard’s sodium dichlor formulation oxidizes organic impurities in water, such as sweat, oils, and dead skin cells. This improves water clarity and can help reduce cloudiness. It also gets rid of chloramines, which cause a strong odor in chlorine spas and hot tubs.
Because of its chlorine content, SpaGuard is also able to kill bacteria in the water.
SpaGuard does two other things: it is a flocculantÂ as well as a pH buffer.
As a flocculant, SpaGuard clumps small particles of impurities floating on the water, which helps clear up the water.
As a pH buffer, SpaGuard stabilizes the water’s pH, preventing significant fluctuations. This keeps the spa or hot tub clean, prevents damage to equipment (due to rapid increase or decrease in pH), and ensures the water is safe for users.
SpaGuard comes in a 2-lb bottle with a recommended dosage of three tablespoons per 500 gallons.
Issues and Concerns
SpaGuard is not ideal for swimming pools. It’s not that you can’t use it, but that it would end up being expensive because you’d need several bottles every time you shock your pool.
For pools, even smaller above ground pools, we recommend one of those multi-pack pool shocks. They are more economical.
Something else to note is that SpaGuard is not an algaecide. It can help prevent algae formation and can clear away mild algae levels. But if you have a serious algae problem in your spa or hot tub, it won’t help. Get an algaecide instead.
SpaGuard Enhanced Shock is a great all-round product for regular spa and hot tub maintenance. Its four-in-one functionality keeps water clean, hygienic, odorless, and clear.
7. Best for Quick Sanitizing: DryTec Calcium Hypochlorite Shock
If you need to quickly sanitize your pool, you’ll need a high-chlorine shock. DryTec Calcium hypo contains 68% free chlorine, making it a fast-acting pool sanitizer. It also works great as an algaecide.
- Powerful and fast-acting pool sanitizer.
- Kills algae.
- Good pricing – a single 24-pack lasts most pool owners for several years.
- Doesn’t contain cyanuric acid – vulnerable to sunlight degradation.
- It can damage vinyl pools.
DryTec is powerful stuff. The Calcium Hypo formulation contains 68% chlorine. This makes it a good choice for quick pool sanitation.
The high chlorine levels quickly kill bacteria. Use DryTec to sanitize the pool after heavy use (such as a pool party) or when you are closing down/opening up the pool.
DryTec is also effective against algae, even heavy algae infestations. Add the recommended amount to your pool (1lb for 10,000 gallons) then let it rest overnight. Once your pool filters out all the algae, it’ll leave the water clear and algae-free.
DryTec also oxidizes organic contaminants, gets rid of pool cloudiness, and eliminates the strong smell caused by chloramines.
The largest pack available contains 24 1-pound bags of shock. That’s enough to last most pool owners for several years.
Issues & Concerns
Unlike Sodium Dichlo pool shock, calcium hypochlorite does not contain cyanuric acid, which acts as a chlorine stabilizer. Â Chlorine in DryTec shock is more vulnerable to sun degradation.
To get the most out of the shock, apply it when there’s little or no sunlight. Most pool owners prefer adding it to the pool in the evening and then let it work overnight with the pool pump turned on.
Also, be careful if you have a vinyl pool as DryTec can bleach your pool liner. To be safe, pre-dissolve DryTec in a bucket then add the solution to the pool.
DryTec Calcium Hypochlorite Shock is the best choice for fast and effective pool sanitation. It’s also the best shock for pools with a serious algae problem.
8. Best for Regular Maintenance: In The Swim Chlorine Pool Shock
In Swim chlorine pool shocks are another good choice if you are looking for a powerful shock to keep your pool bacteria and algae-free.
Add this shock regularly to your pool, and you’ll never have to deal with chlorine odors, water cloudiness, or green algae-filled water.
- Powerful pool sanitizer.
- Kills algae.
- Good value for money.
- It can damage vinyl pools.
- Lacks cyanuric acid – sunlight will reduce its effectiveness.
In the Swim, pool shock has a calcium hypochlorite formulation with at least 65% available free chlorine. This makes it highly effective against bacteria and algae.
It’s especially great if your pool gets a lot of heavy use. You can use the In the Swim shock to keep the water bacteria and algae free.
It’s also effective for neutralizing chloramines, the chemicals that cause itchiness, and chlorine smell.
There’s a 12 and 24-pack available, each consists of 1-pound bags. The recommended dosage is 1lb for 10,000 gallons.
Issues & Concerns
Be careful when using In the Swim shock as it is powerful. If you have a vinyl pool, we highly recommend pre-dissolving it in a bucket of water before adding it to the pool. This prevents undissolved granules from settling at the bottom of the pool and bleaching your liner.
Something else to note is that the In the Swim shock doesn’t have cyanuric acid. Avoid adding it to the pool when it’s sunny, especially if your pool is not shaded.
In the Swim, shock makes pool maintenance much easier by preventing bad stuff like algae and bacteria. We highly recommend it for the regular pool maintenance, especially for heavily-used pools.
How To Choose The Right Shock For Your Pool
Here’s what to consider when buying pool shock.
Calcium hypochlorite is the most powerful type of pool shock. Use it when you want quick sanitation or to get rid of algae.
Sodium Dichlor is the best choice if your pool or exposed to strong sunlight. Cyanuric acid added to the formulation prevents chlorine from being degraded by the sun.
Non-chorine shock is a good choice if you find chlorine shock too harsh. Just remember that non-chlorine shock is mostly effective against chloramines and organic contaminants. For sanitation (bacteria & algae removal), chlorine shock is a better choice.
Some pool owners opt to get both chlorine and non-chlorine shock. They use non-chlorine shock for regular maintenance and stronger chlorine shock for situations where the pool needs deep sanitation, such as during opening/closing, in case of algae, bloom, or after heavy use.
When buying pool shock, always check the amount of available chlorine it contains. The higher the amount of chlorine, the more powerful the shock is.
High chlorine levels are not always the best. For regular maintenance, a pool shock with 40-50% available free chlorine is enough to keep your pool clean and sanitized. A lower amount of chlorine is also safer for vinyl pools.
But if you are dealing with serious algae bloom or it’s been some time since you cleaned the pool, look for a shock with 60% chlorine or higher.
Liquid vs. Granular
Granular pool shock is the best for most pools. It’s stronger than liquid chlorine and thus more effective against algae, bacteria, and other contaminants.
The only concern with granular pool shock is damage to the liner. If you have a vinyl pool, we recommend pre-dissolving the shock in a bucket before adding it to the pool, especially if you are using shock with chlorine levels above 60%.
Swim Wait Time
If you use your pool daily, or several times a day, look for a pool shock with less waiting time. Some lower-chlorine shocks dissolve fast, and you can get into the water after just 15 minutes.
Non-chlorine shock also has very little waiting time. You can usually get into the pool immediately after you shock it.
Calcium hypochlorite shocks have a longer waiting time since they have higher levels of chlorine. In some cases, you have to wait up to 24 hours before the pool is safe to swim in.
Note: Regardless of what the label or manufacturer says, only get into the pool once chlorine levels fall to between 1ppm and 4ppm. Use a chlorine test kit to check chlorine levels.
Some pool shocks have a multi-functional formulation. They act as a sanitizer, algaecide, and oxidizer, all in one.
These additives can ease maintenance since you don’t have to use a bunch of different products to keep your pool clean.
How to Shock Your Pool?
Here’s a general step-by-step guide on how to shock your pool. Check the label on your pool shock for specific instruction.
1. Check Pool pH
Your pool’s pH levels determine how effective the shock is. If the pH is too high, most of the shock will be wasted. A pH of 7.2-7.4 is the best for shocking.
Test your pool’s pH, and if it’s too high or too low, adjust it to the right level. You can lower pH using muriatic acid while baking soda is perfect for raising pH.
2. Add Pool Shock
Once your pool’s pH is at the right level, it’s time to add the shock. Depending on the type of shock as well as your pool, you may need to pre-dissolve the shock first in a bucket before pouring the solution into the pool.
This is usually recommended for high-chlorine shocks and vinyl pools.
For shocks with less chlorine or non-chlorine shock, you simply pour the granules directly into the pool. Brush away any granules that settle at the bottom.
Make sure you follow the recommended dosage. The standard dosage for most pools is 1lb for 10,000 gallons. But if your pool is very contaminated, you can add more shock.
Once pool shock does its job, there will be plenty of contaminants floating in the pool, including algae. Run your pool pump for 12-24 hours to filter out impurities.
Most shock labels recommend turning the pool pump on when you add shock. This will ensure your pool achieves maximum clarity; in other words, a deep blue look.
You can also use an automatic pool cleaner to remove any remaining impurities.
Frequently Asked Questions
How much pool shocking do I need for my pool?
It depends on the volume of water in your pool and how contaminated it is. The standard dosage for the most pool is 1lb of a shock for every 10,000 gallons.
How often should I shock the pool?
Every 1-2 weeks. Shocking your pool regularly prevents algae from taking hold and keeps the pool sanitized.
Also, shock your pool after it’s been heavily used, after an exceptionally hot day (chlorine levels drop when it is sunny) or after a storm. It’s also a good idea to shock the pool when you open it and close it down.
Liquid shock vs. granular: which is the best?
We recommend granular shock. It is more powerful and more effective against bacteria, algae, and other contaminants.
Will pool shock damage my pool?
If you have a vinyl pool, be careful when adding pool shock. If the shock has high levels of chlorine (50% or higher), pre-dissolve it in a bucket of pool water, then pour the solution into the pool.
This prevents the granules from bleaching your pool liner.