Why should I shock my pool? Or perhaps you are wondering how to shock a pool?
I have the answers to these and more questions pool owners ask when maintaining or treating their facilities.
But before that, it is critical to note that swimming pools are shocked to eliminate chloramines or combined chlorine molecules from the water.
They are also shocked to get rid of bacteria, excess bather waster, algae, contaminants.
A bromine-treated water body also requires a shock to reactivate the bromide ions in that water.
Shocking a pool is the ideal way to give it life by balancing it through breaking up chlorine and contaminants or combined chlorine.
Types of Pool Shock: Non-Chlorine Shock vs. Chlorine Shock
Knowing how to shock a pool can be handy when treating your facility. Still, it is equally critical to understand the right shock product.
You can find different types of pool shock on Amazon, online pool shops, and even your local pool stores.
Despite that, you will eventually get to decide between the non-chlorine vs. chlorine shock.
Four Types of Chlorine Shock
The market offers four types of chlorine shock that do the shocking effectively, but they differ in many ways.
These are Dichlor and Trichlor, Sodium Hypochlorite (liquid chlorine), Calcium Hypochlorite (cal-hypo), and Lithium Hypochlorite (lithium).
The three variations contain chlorine as their primary ingredient, with the other ingredients affecting how they work.
Note that one type of chlorine shock might be best suited for your swimming pool than the other – it depends on your pool’s condition.
- Lithium Hypochlorite
This is the most expensive way to shock your pool.
However, it dissolves quickly, making it perfect for vinyl-lined pools or surfaces prone to bleaching.
It doesn’t add calcium to the pool or leave residue in the water or walls. The product is mainly recommended for hard water.
Lithium shock also requires you to add a high dose to enjoy its impact – about 1 pound per 8000 gallons of water.
The high dosage and cost make it only ideal for a small pool. Most commercial pool owners don’t use it.
- Calcium Hypochlorite
You now know the most expensive way to shock your pool, and now I give you the cheapest way to shock a pool.
Why do I say it is the cheapest way to shock a pool? That’s because it is affordable and convenient to use.
It is found in a granular or powder form, and you can choose from different strengths.
You only require about 1 pound of the product to treat 10,000 to 15000 gallons of water, depending on the strength.
The major downside of this shock is the high pH level, meaning you should only be used in pool surfaces that resist bleaching.
It can also boost the free chlorine without affecting the cyanuric acid (CYA).
CYA acts as a sunscreen for chlorine by protecting it from the degrading UV light from the sun.
Cal-hypo also increases the calcium level in the pool.
- Liquid Chlorine
This type of chlorine is relatively affordable and has the highest level of pH of all chlorinated shocks.
It can bleach liners, vinyl, paint, and other sensitive and soft surfaces.
You also require about 1 pound of this product for every 10,000 gallons of water, making it a low dose shock.
The product turns into saltwater when it is fully oxidized.
- Dichlor and Trichlor
The last type of chlorinating pool shock is dichlor and trichlor.
These are stabilized chlorine, unlike the other three, that can withstand the degrading UV rays.
They come in slow-release sticks, tablets, or pucks and help to sanitize outdoor swimming pools.
You can also find these products in granulated form and have a high chlorine level, making them ideal for heavy-duty algae infestation.
Pros and Cons of Chlorine Shock
The chlorine shock provides the following benefits:
- Removes ammonia and chloramines
- Purify water by oxidizing organic contaminants
- It kills bacteria and algae easily
- Help to disinfect the pool water
- Cal Hypo is the cheapest way to shock a pool
They have the following shortcomings:
- It can easily damage the pool surface
- Cal Hypo can add calcium to the pool water
- Hazardous to use and store
- A strong odor
Best Uses of Chlorine Shock
The products do more than just removing the chloramine and contaminants in the pool by:
- Removing Algae: They are effective in treating a pool with a high infestation of algae.
The granular models are the perfect treatment for pools with algae.
- Removing Bacteria: They penetrate the bacteria’s cellular membranes to destroy them from inside.
Types of Non-Chlorine Shock
Non-chlorine shocks or chlorine-free shocks have a pH between hand soap and ocean water, which is nine.
They have a lower pH than the chlorinated models, meaning you can swim 15 minutes after adding them.
These products don’t bleach the liners, swim trunks, or paint and have “Oxy’ in their names to show they contain oxygen.
Non-chlorine shock also contains salts of potassium and are often called MPS or MonoPerSulfate, or Potassium Peroxymonopersulfate. Non-chlorine
You can also call them Oxone or non-chlor and offer some benefits and shortcomings alike.
Pros and Cons Non-Chlorine Shock
Here are the advantages of the chlorine-free shock:
- No odor, no residue
- They don’t interfere with the pH level
- Purify water by oxidizing organic materials
- Removes ammonia and chloramines
- Can be added directly to the pool
- Won’t fade or bleach the swimsuits or vinyl liners
- Don’t add cyanuric acid or calcium to the water
Their main drawbacks include:
- About 10% more expensive than chlorinated shock
- Not ideal for pools with algae and bacteria
Best Uses of Chlorine-Free Shock
You can use the non-chlorine shock to:
- Remove Chloramine: They help to break apart molecules of combined chlorine and remove foul odor.
- Remove Contaminants: You can use them to attack daily infestation of organic and natural contaminants that might end up in the water.
These include bird droppings, leaves, dirt, grass clippings, dust, swimmer waster, and body oils.
Non-Chlorine Shock vs. Chlorine Shock: Which One to Use?
There was a big difference between the prices of these two types of pool shock, but now it is almost equal.
The chlorine-free shock offers more benefits and can act as the only oxidizer in the pool.
That can mean avoiding using chlorine shock in case of a high bather load, algae blooms, or during a pool opening.
You should consider using the non-chlorine shock for general chloramine and contaminant removal or general pool filtration and sanitation.
They have fewer and gentler “side effects” than chlorinated models, but they are about 10% more expensive.
With that in mind, I would recommend you use both: chlorine shock when your pool needs a potent shock and non-chlorine shock for oxidation.
What is Shocking a Pool?
Shocking a pool is the process of adding pool chemicals to a swimming facility.
The process aims to provide the same results whether you use an inground or above ground pool shock, which is:
- Kill bacteria, algae, and every harmful pathogen in the pool
- Raise the chlorine level in the pool
- Break apart combined chlorine or chloramines
Shocking your swimming pool is a critical process of guaranteeing a healthy swimming facility for all swimmers.
Why Do You Shock a Pool?
Why should I shock my pool? There are several reasons to shock a swimming facility.
I have listed the common reasons why pool owners add the shocks in the water:
- Free Chlorine Good, Chloramines Bad
The primary reason for shocking a pool is to break up the combined chlorine or chloramines.
You can measure three kinds of chlorine in your swimming facility: free, combined, and total chlorine.
- Free Chlorine
This type of chlorine is free to interact with bacteria, algae, and other pool chemicals.
Pool owners like this kind of chlorine because it interacts with the harmful material, kills them, and then sends them (off-gasses) to the atmosphere as a gas.
It then continues with its “free lifestyle” to look for its next victim.
- Combined Chlorine
Combined chlorine is often stuck in an unproductive relationship, more often with nitrogen and ammonia.
It is not free to interact with contaminants in the water, making it an ineffective sanitizer.
This kind of chlorine remains in the combined state unless it gets help from a pool oxidizer or free chlorine.
You can easily detect the presence of the combined chlorine thanks to its stinking nature of a strong chlorine smell.
- Total Chlorine
It is the total of the combined chlorine and free chlorine.
Shocking your pool releases the combined chlorine, off-gasses the contaminates, and helps to boost the level of free chlorine in the pool.
The choice of using a non-chlorinated or chlorinate shock depends on the amount of total chlorine in the pool.
- Use a chlorinate shock if the level of total chlorine is low.
- Use a chlorine-free shock if the total chlorine level is high.
You should aim to raise the level of free chlorin 10x that of the combined chlorine to reach the “breakpoint.”
That makes it vital to rectify the combined chlorine when it is small. I would recommend you seek professional help when trying to hit the breakpoint.
- 3-5ppm Good, Zero Chlorine Bad
Another critical reason for shocking the swimming pool is to boost the level of sanitizer fast.
The chlorine level in the water can bottom out due to different reasons, like after a party.
It would help if you increased this level to 3-5ppm quickly before bacteria and algae can infest your pool.
This is the time to use a chlorine shock.
- Swimming Pool with Algae
You should also shock your pool if you find algae bloom or any other problem.
It is a way to raise the chlorine level temporarily to deal with this problem.
- Pool Close-Down and Start-Up
Most pools get winterized and require to be shocked when opened for the first time after the long close-down.
The shocking should be done after the water chemicals are balanced. It helps to kill bacteria, algae, oxidize particles, and restore water clarity.
Pool shock should also be used before closing the facility to disinfect the water.
- After a Heavy Rainfall
Rainwater is pure, but it collects airborne particles that get into the pool as it falls via the air.
Algae spores, pollen, dust, and air pollution can affect water chemistry, consume the pool chlorine, and discolor the water.
Overflowing planters, lawn areas, and overhanging trees can also fall into the pool during a heavy storm.
These can add phosphates, debris, and bacteria to the pool.
- Bather Waste and Bacterial
By now, you know that bacteria get into the pool water in many ways. Pathogenic bacteria can also stay in the pool.
Use the shock after a long winter, swimmer “accidents, heavy storm, or heavy pool use to kill the bacteria.
Bather wastes include soaps, cosmetics, skin, lotions, hair, fungus, feces, urine, and sweat.
Time to Shock: When to Shock Your Pool
When should I shock my swimming pool? You should shock your facility when the sun is down (evening) and when the filter is operating.
The chlorine shock will not work if you add it when the sun is hot.
You can have confidence that the shock will effectively circulate all around the swimming pool when the pool filter is running.
You should also not shock the pool when it has swimmers. Other times to shock the pool area:
- Immediately after a pool party to remove the extra bather waste to prevent straining the present free chlorine
- During or after sunny/hot weather, the high temperatures boil out the chlorine from the water. A high temperature also creates the ideal condition for bacteria and algae growth.
- During or after a period of heavy rainfall because rainwater increases the pool water pH. The chlorine doesn’t work correctly if the pH is unbalanced.
How Often Should You Shock a Pool?
Every pool expert would recommend you shock your pool about once per week or at least once in two weeks.
This is critical to maintain the perfect water chemistry and keep the pool ready for use.
That’s the most straightforward answer to “how often should you shock a pool.” Still, there are many factors to consider when deciding when to shock your facility.
For example, you might want to shock your swimming pool regularly if you often hold parties.
That will ensure you have a clean facility for people to dive in and enjoy your parties.
You should also consider shocking your pool regularly during the heavy rain season.
It is recommended to use about 2-pound of shock per 10,000 gallons of water during the weekly pool maintenance.
Pool Shock Treatment Instructions: 6 Steps of Shocking Yours Pool
Let me now teach you some universal pool shock treatment instructions. You can apply the six steps when shocking with most pool products.
- Wear Protective Gears
Pool shocks are chemicals that can bleach your clothing or harm your skin, ensure you protect yourself.
That includes wearing protective eyewear, gloves, and clothes you don’t use or mind running.
- Prepare the Shock/Chemicals
The first thing is to choose suitable chlorine or chlorine-free product for your swimming pool.
From there, read the manufacturer’s instructions on the packing and prepare the shock accordingly.
For instance, you need to dissolve granular shock in a bucket of water before you add it to your pool.
Lithium hypochlorite can be added straight to the pool without any preparation.
The preparation stage also involves knowing the right amount of shock to add to your pool – you should know your pool’s size.
- Shock Your Swimming Pool
You can now pour the water and shock solution into your facility, following the manufacturer’s guidelines.
Some brands will tell you to pour it near the jet, while others will ask you to disperse it around the edges.
- Leave the Pool for the Shock to Work
It is time to relax and leave the solution to do its magic.
The brand’s instructions are critical here to prevent swimmers from entering the pool too soon.
Most pool experts will recommend you leave the pool to settle overnight.
- Check the Water Chemistry
You still need to test the pool’s calcium hardness, total alkalinity, pH, and chlorine levels after waiting the recommended time.
Ensure that everything is balanced before you let the swimmers in the water.
Note that a pH level of about 7.2 is required here for the shock to work correctly.
Anything over 8.0 would render the shock useless.
- Let the Filtration System Remove the Contaminates
Shocking the pool will kill bacteria, algae, and germs, but it will not remove them from the water.
That is where the pool filtration system comes in handy. Make sure you run it for about 24 hours.
How to Shock a Pool: FAQs
Pool shock helps to keep the pool water chemistry balanced while killing contaminants and algae.
Here are some of the commonly asked questions about the pool shocks and their answers:
Best Time of Day Shock Pool?
You should consider shocking your pool in the evening or when the sun goes down.
Shocking when the sun is hot or during the day can render the shock ineffective due to the UV rays.
The rays reduce the free chlorine levels.
How Long Does Shock Last in a Pool?
About 80% of pool owners under shock at their facilities because they do not know how long these products last in the water.
Pool experts recommend you conduct regular maintenance of your pool every week and alternate between chlorine-free and chlorine shocks.
That means using the non-chlorine shock to oxidize contaminants on week one and then the chlorine-based one on week two.
The important thing is to test the chlorine levels before deciding which shock to use first.
You can use the Cal-hypo shock to super chlorinate your pool. Such a product will cloud the water for about 12-24 hours.
Professional Tip: You can know that chlorine is ineffective if you can “smell chlorine.”
It is usually combined with ammonia and can no longer sanitize your pool – it is time to shock.
How Long After You Shock a Pool Can You Swim?
Shocking your facility can cloud the water for a few hours, making it vital to give it some time to breathe.
You will interfere with the cloudiness if you jump into the water instantly, meaning that you won’t see any improvement.
If you do a simple Google search, you will find ballpark estimates between swimming immediately and waiting for about 24 hours.
It means there is no one answer to this question. One solution is to shock in the evening and leave the filter running overnight.
But what if something messes the pool at 9 am, and you have a pool party in the afternoon?
You will need to shock it immediately. But how long will you wait before letting the people enjoy the pool?
Here the answer is to wait 60 minutes for every pound of shock you add to your pool.
Whether you shock at night or during the day, always ensure you test for chlorine and pH level to ensure they are in the recommended range.
As a guideline:
- pH range should be between 7.2-7.8
- Free available chlorine should be between 1-4ppm
- Ideally, you should wait for 6-24 hours before swimming
- Wait for about 18-24 hours if you add Cal-Hypo
- Wait for 24 hours if you add other types of chlorine-based shock
How to Shock a Pool After Winter?
There are many steps involved when opening a swimming pool after the winter.
One vital step is shocking the pool, and this is how you should do it (after completing the other processes):
- Test Your Swimming Pool
You have been running the swimming pool pump for the whole day; now, it is ideal for testing the chemistry.
Some people take water samples to their local pool store, while others test the water using pool test kits or strips.
Here you need to test for three things: chlorine, pH, and minerals.
- Balance the Pool Chemicals
Follow this guideline when balancing the chemicals:
- Total Alkalinity – Ideal reading of 80-120. Use muriatic acid to decrease or sodium bicarbonate to increase.
- pH Level – Between 7.2-7.4. Use sodium bisulfate or muriatic acid to decrease or soda ash to increase.
- Chlorine – Perfect at between 1-3ppm. Use granules or liquid to normalize the chlorine level.
- Calcium – Recommended at 150-250ppm. Use calcium chloride to make the water hander if it is too soft.
- Shock Your Pool
Shocking your pool will remove all remaining contaminants and germs in the water.
Follow the product’s instructions when adding chlorine to the water. You can reinstall your auto pool cleaner 24 hours after adding the pool shock.
How Many Bags of Shock to Open Pool?
The level of chlorine at which the molecular bonds break apart is called breakpoint chlorination.
It is the point at which pathogens, algae, and chloramines get out of the pool water.
For most pools, the breakpoint chlorination level is at 30ppm when the order is restored.
Here is a chart with guidelines on the amount of shock you need to achieve a 10ppm level:
- Calcium hypochlorite – 1.3 pounds
- Lithium hypochlorite – 2.5 pounds
- Sodium hypochlorite – 3.5 quarts
- Dichlor – 1.5 pounds
Assume you have 20,000 gallons pools. You would need 7.8 pounds of Cal-hypo to reach the desired point of 30ppm.
Still, you need to test your pool before adding the shock to know the ideal amount to add.
Most brands also include steps or charts with instructions to help you calculate the ideal amount of shock to add to the water.
You can also do compute the number as follows:
Combined Chlorine (CC) = Free Chlorine (FC) – Total Chlorine (TC)
Multiply the CC by 10 (CC x 10)
Subtract the FC from the sum (CC X 10 – FC)
Read the instructions on the shock package to figure out how much shock will produce 1ppm when added to 10,000 gallons of water.
Divide the pool volume by 10K
Multiply the chemical change (d) by the number you got in (e) and then the figure in (c).
Change the result in pound by dividing (F) by 16. It is the amount of shock you will need to add to your swimming pool.
How Much Shock for 10,000 Gallon Pool?
The pool experts recommend using a bag of shock or a gallon of liquid chlorine for every 10,000 gallons of water.
You can always compute the desired shock following the steps above.
Shock Your Pool Every Week
Now you know how to use pool shock, the types of pool shock, the amount of pool shock you need, and other things about these pool products.
You also know why, when, and how to shock a pool. You might need to do some calculations, but it is nothing like a brain teaser.
Regularly using the right shock for your pool will prevent problems in the future.