Shocking is a regular part of your pool maintenance that you will be doing almost every week, if not more. Shocking literally means overwhelming (shocking) bacteria, algae, or chloramines with huge amounts of sanitizing chemicals (generally chlorine).
This sudden rush of chemicals does the job of cleaning but can also be hazardous for us.
In most cases, you need to wait for these chemicals to come down to normal range before you can safely swim in the water.
How long to wait after shocking the pool depends on the type of shock you are using. If you shock your pool with non-chlorine shock, then you can safely swim in the water after 15 to 20 minutes of adding shock. This shock does not contain chlorine; hence is not dangerous. On the other hand, in case of chlorine-based shock, 6 hours are enough to get chlorine levels below 5ppm in most cases. More than the number of hours, you need to check that free chlorine and pH levels are at safe levels before entering the pool.
Read on to learn more details on when to enter your pool after shock.
What does Shocking a Pool Mean
Shocking a pool mostly involves temporarily increasing the free chlorine levels in your water to extremely high levels. This process is often referred to as super chlorination or hyperchlorination.
Over time, chlorine breaks into chloramines, which causes the pool’s odor.
If your pool smells odd, it indicates it requires your attention. When you shock your pool, the high chlorine levels/oxidizer break down the chloramines and eliminate the odor.
Chlorine pool shock will also help eliminate algae growth, cloudy water, and other water quality issues.
When to Shock the Pool for Minimal Wait
When you add shock to the pool, you are adding chlorine in large amounts so that free chlorine concentrations are so high that they can break down any contaminants like bacteria, algae, and chloramines.
You generally add ten times the concentration of combined chlorine. The chlorine levels go above 10ppm when you are shocking the pool.
Such huge concentrations of chlorine can cause skin allergies, eye irritation, and many other problems.
That is why it is recommended to shock your pool at night so that chlorine can work at night when you are not using the pool.
By morning its levels will be down to normal. That way, you don’t have to wait for the chlorine levels to come down, and it also has the other huge benefit in case you use cal-hypo, which is the most commonly used shock.
Cal-hypo shock is unstabilized and is not protected from sunlight. If you use this shock in the sun, it will not be as effective as most of the chlorine will be burned down by Sun.
So when you are shocking at night, by morning, it will be at least 10 to 12 hours, and 99% of the time, chlorine levels will be within safe levels.
Of course, you don’t have to assume; take a free chlorine test, either with strips or a kit. Make sure the levels are below 5ppm or, ideally, below 3ppm.
Types of Pool Shock and How They Affect Wait Time
Many types of pool shocks are available in the market, each with its own advantages and limitations.
The two most common types of shocks are chlorine and non-chlorine.
These are shocks that add a large amount of chlorine to the pool, and you need to wait for some time before chlorine levels get below dangerous levels.
Note: Always test the water before entering the pool after shock, and never assume based on the number of hours. Pool care is not about assumptions, it is all about testing.
Calcium Hypochlorite Shock
This is a chlorine-based shock that contains around 70% chlorine. It is very cheap and comes in the form of granules or powder.
You need to pre-dissolve this unstabilized shock before adding it to the pool, as it is very hard to dissolve.
You must be careful not to add too much at once since this might harm your pool’s liner.
Calcium hypochlorite shock is hard to dissolve and will take some time to mix in the water uniformly. It is recommended to wait 6 or 8 hours minimum for swimming after using this shock.
Sodium Dichloro-S-Triazinetrione (Dichlor) Shock
This shock contains 60% chlorine and dissolves fast. It is also known as “Dichlor.” It is a very potent oxidizer that will take care of organic pollutants from your pool’s water.
Be sure to thoroughly read and follow the instructions on the packaging before using this type of shock. Dichlor overdosing in your pool might be harmful.
You can add it immediately to the water; there is no need to dissolve it first. It can also be used for saltwater pools.
It is a stabilized chlorine shock and can be used during the day.
You can use the pool after 6 to 8 hours of adding this chemical. However, as always, test before entering.
Sodium Hypochlorite Shock
This is another chlorine-based shock. But it is different than others as it is liquid in form.
This is not equally potent shock as others, as the concentration of chlorine in this type of shock is around 15%. You need to add a much larger amount of liquid chlorine to reach the same level of effect.
You can read the instruction and find out the volume.
The benefit of this shock is that it does not have to dissolve in water as it is already in liquid form. It will take less time to dissolve hence you can start using your pool early.
After using liquid shock, you can test the water after 6 hours to see if the levels of chlorine have come down.
But as it is also an unstabilized shock, it is best used at night time.
Potassium peroxymonosulfate shock is a non-chlorine shock and is also called “ShockOx.”
It works by oxidizing the water and breaking down organic pollutants in water.
This chemical is highly effective and keeps the chlorine levels in your pool from rising.
This is recommended as a weekly shock for well-maintained pools.
Although it is suggested for shocking saltwater pools, you cannot use it as an algaecide because it is not Chlorine based.
Using it around swimmers and pets is also safe. This is the better option if you want to use your pool immediately after the shock. You just need to wait for 15 to 20 minutes after shocking the pool.
So in case you have a pool party in the afternoon, and your kid pees in the pool, this shock is the best to clean your pool.
Other Factors That Affect How Long You Have to Wait
There will be a few other things that will have a say in when you can use your pool.
Dosage of the Shock
The more amount of shock you use, the longer it will take for it to come down.
Generally, you add 3 to 5 times of normal chlorine concentrations to shock your pool. But if you have cloudy water or other issues like chlorine demand, you may need to add more chlorine-like 10x.
In that case, free chlorine levels will be very high in the water, and it may take 12 to 24 hours for them to get down.
Your chlorine does not do well in sunlight. So if you are shocking your pool in direct sunlight (especially with unstabilized chlorine), the chlorine levels will come down very fast.
For example, it may take 6 to 8 hours at night for chlorine levels to come down, but in direct sunlight, your pool chlorine levels can come under control in 2-4 hours.
Type of Pool
If you have an indoor pool, it will take more time for the shock to come down compared to outdoor pools.
So you have to wait longer after shocking in case you have an indoor pool.
More than anything else, it has to do with sunlight, as indoor pools get less or no sunlight.
If you are shocking your pool to get rid of algae, then you need to use higher doses of chlorine shock than normal.
So it will take more time for free chlorine levels to come down, and you need to wait longer to swim in your pool.
What to Do After Shocking the Pool
After adding the shock to the pool, you should keep running the pump till all the shock is properly mixed throughout the pool.
For example, if you added the shock in the night, keep the pump running overnight so that pool is shocked at each corner.
While the pump and filter are running, keep waiting for chlorine levels to come down to normal levels before diving in.
Decide Based on Chlorine Reading Than Time
On the question of how long to wait to swim after shocking the pool, my advice will be to experiment a bit in starting.
Every pool is different, and depending on the chemistry of your pool, it may take less or longer than the usual 6 to 8 hours for the chlorine to go down.
Decide based on the chlorine reading when to enter the pool and not on time. Only enter the water when chlorine is below 5ppm (ideally below 3ppm) and pH is between 7.2 to 7.6.
And when to take that reading will depend on your experimentation. If, with your routine process of shocking the pool, the chlorine levels come down in 6 hours, then from next time onwards, start testing after 6 hours.
Here are a few frequently asked questions.
What happens if you swim in a pool that was just shocked?
Shock contains a very high dose of chlorine, and it can be hazardous for swimming in freshly shocked water. You may experience skin irritation, itching, eye, and lung irritation. Your hair may turn green, and your swimwear will bleach very fast.
What to do if you accidentally swam in a shocked pool?
Water with very high levels of chlorine can be hazardous and lead to many problems for the skin, eyes, and lungs. If you accidentally entered a freshly shocked pool and started feeling these problems, get out of the water immediately and change your clothes.
Rinse yourself in fresh water immediately for 10-15 minutes.
If your eyes are itchy, keep them open and rinse slowly with fresh water for a few minutes.
In case of more severe symptoms like nausea and vomiting, immediately contact a doctor or emergency services.
How long to wait for swimming after adding regular chlorine?
Chlorine takes some time to dissolve, so it is advised to wait 10 minutes to an hour before swimming after adding a regular dose of chlorine in the form of granules. In the case of tablets, if you are using a floater, take it out before swimming, as it can make concentrated areas of chlorine.
Can I swim 12 hours after shocking pool?
Yes, in most cases, 12 hours will be more than enough to get chlorine levels below 5ppm. However, always test the water for chlorine levels before going in the water. It may happen that you have used overdose or the day is very cloudy, and due to that, levels of chlorine are not down even after 12 hours. So always do the testing.
How long to wait for swimming after adding other chemicals?
It is generally recommended to wait at least an hour after adding any chemical, as it takes some time for chemicals to dissolve and circulate throughout the pool. However, the dissolving time for different chemicals may vary, so always check the manufacturer’s guidelines on this.