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When should I shock my pool? [open]
During swim season, you should shock your pool every couple of weeks. You’ll also want to shock your pool whenever your pool has too low of a free chlorine level or too high of a combined chlorine level. Your environment may affect how often you shock your pool. Heavy rains and storms can dilute the chemicals in the pool water while adding bacteria. [Shop All Shock]
Can I shock my pool to fight algae? [open]
Algae can begin to form in your pool after rough weather due to the spores constantly floating through the air. You must kill the algae quicker than it can reproduce, it also causes your chloring to become less effective. When you notice algae forming in your pool, you can try and shock your pool. It may prove to be a hard task to rid your pool of algae so follow the rule that the more algae there is, the more shock you should add. If the algae in your pool proves to be chlorine resistant, try shocking again or purchase an algaecide. Algaecide can help you keep the chemicals in your pool balanaced and rid your pool of that pesky algae. [Shop All Shock]
What type of shock should I use? [open]
For regular maintenance, you can use chlorine-free or chlorine shock. If you see algae starting to grow, you’ll want to use chlorine shock or super shock. If you have an algae bloom that’s already grown, try using super shock. If you have a severe algae bloom, you’ll want to consider a larger dose of super shock or mega shock. [Shop All Shock]
How much shock should I use? [open]
How much shock you should use depends on how large your pool is, why you are shocking your pool and what type of shock you’re using. You should always check the amounts recommended on the bag, but here is a rough estimate to base your measurements on:

To boost your chlorine levels, we recommend ½ lb — or ½ of a bag — for every 10,000 gallons of water.

If your water is cloudy, we recommend 1 lb — or 1 bag — for every 10,000 gallons.

For treating algae, we recommend 2 to 6 lbs — or 2 - 6 bags — per 10,000 gallons depending on the severity of the algae. The greener and darker the water, the more shock you should add. If you use a stronger shock, you may not need to use as much. [Shop All Shock]
How many gallons does my pool hold? [open]
You’ll need to find the volume of your pool. Here’s a quick formula you can use:

Length x Width x Average Depth x Multiplier = Volume in Gallons
  • Multiplier for rectangular and square pools is 7.5
  • Multiplier for oval pools is 6.7
  • Multiplier for round pools is 5.9
Note: All measurements should be in feet, including the depth. For above ground pools, assume that the water depth is 6” less than the wall height, so if your pool is 48”, assume the depth is 3.5’, and for a 52” pool, use 4’.

If math isn’t for you, take a look of the chart below featuring common pool sizes and how many gallons of water each size holds.

For more help with calculating your pool size, visit our blog, How to Calculate the Number of Gallons in Your Pool.
Do I need to have a certain pH balance to shock my pool? [open]
Similar to adding chlorine, you want to make sure your pH is in the proper range, between 7.2 and 7.6. Once your pool’s pH rises above 8, the shock will be half as effective. [Shop All Testing Supplies]
Are there any safety practices I should follow? [open]
Like any chemical Chlorine shock can be dangerous and should always be handled with care. Always follow the instructions for the shock carefully. When working with shock, you should wear goggles, gloves and a protective mask. Do your best to avoid inhaling from the containers and never mix different types of pool shock. And always keep your pool shock in a cool, dry area away from other chemicals.


Shock is an essential part of maintenance for chlorine pools. It’s a granular oxidizer and powdered form of chlorine added to pools to treat, sanitize and clear water, and it has multiple uses such as fighting algae. Quickly adjusting your chlorine levels, shock has multiple uses. There are several different types, such as chlorine-free shock, chlorine, super shock and mega shock.
Understanding Chlorine [open]
Chlorine is a necessary part of a clean pool and needs to be measured regularly. As you measure chlorine, there are 3 measurements taken: free chlorine, combined chlorine and total chlorine.

Free chlorine is an effective chlorine available to sanitize your pool water and kill contaminants. Combined chlorine is non-effective chloramines that form when there is too little free chlorine. The total chlorine is the measure of both types.

The goal is to have no combined chlorine while the total chlorine matches the level of free chlorine. When trying to remove chloramines, you want to add 10 times the amount of combined chlorine with shocking your pool. This will get you to the chlorine breakpoint. [Shop All Chlorine]
Chlorine vs. Chlorine-Free Shock [open]
Not all shock is chlorine shock. At PoolSupplies.com, we carry several non-chlorine shocks in addition to chlorinated shocks. Non-chlorine shocks use potassium peroxymonosulfate and is near pH neutral. These shocks can be added directly into your pool at any time and is safe to swim in after 15 minutes. Although non-chlorine shock is less expensive than other shocks, they do not effectively kill algae as well as chloring shock.

There are several different types of chlorine shock, but they are all fast acting. They purify water, remove chloramines and ammonia and kill algae. While effective, they require a waiting period of 12 to 24 hours before your pool is safe to swim in again and can sometimes leave behind a cloudy residue. [Shop All Shock]
Shock, Super Shock & Mega Shock [open]
As you go to purchase chlorine shock, you’ll notice 3 main types: shock, super shock and mega shock. The difference between these types is their active ingredient and how much of the active ingredient it has, as well as the available chlorine content is.

Shock is a common type of shock, made with 99% sodium dichloro-s-triazinetrione dihydrate as the active ingredient and has an available chlorine content of 55.5%. When you are shocking your pool for routine maintenance, this type of shock will be sufficient.

The active ingredient in Super Shock is calcium hypochlorite. It is made up of 68% calcium hypochlorite and has 65% available chlorine content. Super Shock should be used when you have cloudy water and notice algae growing.

Mega Shock is the strongest type of shock with 73% calcium hypochlorite as the active ingredient and an available chlorine content of 70%. This should be used when you have a large algae bloom and want to hit it with the strongest available shock. [Shop All Shock]
More Questions?
If you still have questions about pool shock or are unsure what to buy, visit our blog, The Beginner’s Guide to Shocking Your Swimming Pool, call our in-house pool experts at 1-800-356-3025.