Today you're going to learn how to shock a pool FAST ...
In six EASY steps.
When you're done reading this guide on pool shocking, you'll understand everything there is to know about what pool shock is, why you need to shock your pool, when to shock your pool, how to shock your pool, and the different types of pool shock to use.
Best of all: pool shocking is REALLY easy to do and will keep your pool clean and algae-free.
Let's dive right in!
How to shock a pool in 6 steps
In a minute, we'll get to all the facts about pool shock, what it is and why it’s important, but for now it’s time to get down to business and get your pool shocked. This step by step guide will teach you how to shock a pool and keep your pool chlorine level stable.
Here's how to shock your pool in six easy steps.
Step 1. Protect yourself
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Pool shock can harm your skin and bleach your clothing, so make sure you wear clothes you don’t mind ruining and gloves and protective eyewear. When you shock your swimming pool, take care to protect your skin and clothing before getting started.
Step 2. Prepare the chemicals
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Once you’ve chosen your pool chlorine shock, you'll need to read the manufacturer’s instructions and prepare the shock accordingly. Following the instructions is crucial for ensuring that the chemicals work properly. Also, if you have a saltwater pool, you will want to use a non-chlorine shock treatment.
For example, granular shock will usually need to be dissolved in a five-gallon bucket of water before it’s poured into the pool.
But other shock, such as lithium hypochlorite can be poured straight into the swimming pool in.
You'll also need to determine the proper amount of shock to use with your particular size of pool and prepare the shock accordingly.
Step 3. Shock the pool
Poor the shock and water solution into the pool according to the manufacturer’s instructions.
Some will recommend you disperse the pool chlorine evenly around the edges and others will tell you to pour it in close to the jets to circulate it throughout the swimming pool. Look at the instructions to learn what method is best for the chemicals you are using and your pool.
Step 4. Leave it alone
Leave the chlorine shock in the pool water to do its work.
The manufacturer’s instructions are important here as well to make sure no one gets in the water too soon after treatment.
It’s usually recommended that you leave the chemicals in the pool overnight.
Step 5. Check your pool chemistry
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After you’ve waited the recommended number of hours, you still need to test your pool’s chlorine levels (pH, total alkalinity, and calcium hardness especially) before letting anyone swim in the pool water.
Make sure the levels have returned to normal before you allow anyone in the water.
Note that low pH levels in the pool are important here: if your pH level is over 8.0, your pool shock is basically useless. Shoot for a pH level of around 7.2 if you need to lower it.
Step 6. Run the filtration system
While shocking your pool will help kill and germs any algae, it won't actually get rid of them; for that, you need your filter.
So be sure to run your pool filter for at least 24 hours before swimming. Running your filters is an important part of pool maintenance and will help ensure that the water is clean.
What is pool shock?
The process of shocking your pool is simply super-chlorinating it in order to kill the buildup of chloramines and anything else floating around that doesn’t belong in the pool water.
What are chloramines, you ask?
Chloramines, or combined chlorine, are what get into your pool when chlorine disinfectants combine with the sweat, oils, and (yes) urine from the people swimming in your pool.
So when you shock your pool, you're adding enough chlorine and chemicals to destroy the chloramines.
Why you need to shock your pool
Whether you're a brand new pool owner or a veteran, you need to be familiar with the process of shocking your pool.
Certain living organisms can still survive in your pool with its normal chlorine amounts. Others can become completely immune to it, which is where pool shocking comes in.
There are basically three reasons to shock your pool:
- Sunshine breaks down your chlorine, causing it to lose up to 5 ppm per day.
- Swimmers are constantly bringing in contaminants like makeup, sweat, and bacteria that normal chlorine levels can’t always fight.
- Heavy rain can dilute your pool, leaving you with very low chlorine levels in the water.
When to shock your pool
Most people only decide to shock their swimming pools when they see an overgrowth of algae or they start getting cloudy pool water, but by this time, cleaning your pool could take a lot more work. It's best to shock your pool before cloudy water appears.
So if you stay on top of this chore by shocking your pool once a week, you may be able to avoid an algae overgrowth.
This kind of water contamination often requires way more scrubbing, vacuuming and sometimes even draining than you will ever want to do.
BUT…in case you are like the rest of us and occasionally put things off, here are the times when you should shock your pool even if you don’t feel like it:
When free chlorine levels drop below 3 ppm
Let's first talk about the differences between free chlorine, combined chlorine, and total chlorine.
Generally, the goal is to raise your free chlorine to about 10x the level of the combined chlorine (commonly known as "break point chlorination").
Most pool test strips won't be able to measure combined chlorine and total chlorine, so you'll have to use a pool test kit to do this job.
When your free chlorine levels drop below 3 ppm, it's time to shock your pool.
Before you first use your pool for the season
Your pool definitely needs a pre-boost of chlorine before everyone starts jumping in with all their germs. Additional free chlorine is especially important if you’ve had a cover on the pool all winter.
Who knows what might be lurking under the water?
Before you cover it up for the winter
If you are about to close up shop, there could be algae spores or other matter in the pool just waiting to make a home in your crystal clear water.
Get ahead of it by killing it with chemicals before it grows!
After extreme weather conditions
Heavy wind or rain can carry in debris and algae spores into your pool that can get out of hand quickly if you don’t take charge immediately, and can also cause a significant water level change in the pool.
After heavy pool use
Did your kids recently have a pool party? All kinds of icky junk can be transported into the water by humans and pool toys.
Get rid of that leftover sweat, makeup, and who knows what else with chlorine shock before it clouds up your water.
At the first sight of algae
Algae spores can bloom and spread quickly in the water. Don’t let your pool get overtaken before you take action! Make pool care a top priority, use effective cleaners, and shock your pool frequently.
Types of pool shock
There are several different types of pool shock on the market and it’s important to research the difference before you decide which shock is right for you.
You can pick any of these chemicals up on Amazon or at your local pool store.
- Powerful chlorine shock treatment that is great for regular maintenance.
- Quickly eliminates algae, bacteria, and other harmful contaminants from your pool water.
Calcium hypochlorite is usually granular and also sometimes called cal-hypo shock.
According to American Chemistry Council, it “destroys germs that are capable of causing numerous health problems for pool users--diarrhea, swimmer's ear (a nasty earache) and various respiratory, skin and wound infections.”
This is the most popular shock purchased because it’s considered the strongest shock and it’s also the cheapest.
The chemical dissolves quickly and should be used at night because it’s adversely affected by sunlight hitting the water.
Lithium hypochlorite is usually used in pools with high calcium levels because it doesn’t contain calcium itself.
You don't have to pre-dissolve it, making it slightly more convenient than other shocks.
This is a granular chlorine that dissolves slowly, so it’s cleaning power lasts longer than cal-hypo.
It has a neutral pH level and is another highly popular pool shock because of its availability. It is also one of the best shocks for saltwater pools. However, be aware that DiChlor shock can cause your cyanuric acid levels to rise in your pool.
Potassium peroxymonosulfate (non-chlorine shock)
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Popular with vinyl liner pools, this shock is oxygen-based instead of chlorine-based, and it oxidizes the pool water and boosts chlorine levels.
People can actually swim very soon after this chemical treatment is applied so it’s a popular shock to use in between super-chlorinating during heavy swim times.
Frequently asked questions
Shocking the pool can be a little intimidating at first, so here’s some answers to the most frequently asked questions about how to shock a pool:
Q. What's the best time of day to shock?
Most pool shocks are best used at night so that the sunlight doesn’t decrease its effectiveness in the water.
It’s also best to shock your pool at night so that it can be left alone for several hours, giving it time to work.
Q. How long does it take to shock a pool?
The actual shock process shouldn’t take more than an hour, but depending on the chemical used, it could be up to 8 hours before you can use your pool.
Q. How long after shocking is it okay to swim in?
When using a chlorinated shock such as dichlor or cal-hypo, you will need to wait the recommended amount of time before swimming, usually overnight.
When using a non-chlorine shock, however, it’s usually safe to swim about 15 minutes after shocking the pool.
Bottom line on shocking a pool
Nobody likes a dirty pool.
Take it from me—if you shock your pool once a week, it will save you HOURS of cleaning time in the long-run and keep your pool safe to use. Shocking the water regularly is one of the best forms of pool care.
Killing algae spores and bacteria before they spread is the number one way to stay ahead of pesky pool maintenance tasks once and for all. So, don’t neglect it.
Shock your pool on Monday and enjoy it the rest of the week!
Hi, I’m Matt Harper, the founder of poolcareguy.com, a site I started with one simple mission: to help people around the world clean and take care of their pools and hot tubs on their own, without the hassle.
I’m not a professional pool cleaner and don’t have any formal training, I’m just an average guy who loves hanging out by his pool and hot tub and taking care of it. After many years on the job, I’ve become quite good at it.
On this website I will be teaching you absolutely everything I know about pools and hot tubs.