There is a lot of uncertainty about swimming pool shocking methods and products when there really doesn’t need to be. Shocking your pool is an effective and simple process used to clean green pools quickly. To avoid wasting your time, I will first answer, as plainly as I can, the question: How do I shock my pool?
- Remove dirt and debris out of your pool.
- Add chlorine to raise the free chlorine level to 10 – 30ppm.
- Maintain that free chlorine level for as long as you need to until your pool water looks clear.
- Do an “Overnight Chlorine Loss Test” to verify that the algae in your pool is dead.
You might have noticed that I did not include any kind of “pool shock products” in the process, that’s because “pool shock” is just chlorine in higher dosages. You can shock your pool using normal chlorine alone.
Depending on the size of your pool, you will need to adjust how much chlorine you should add to the water in order to raise the free chlorine to shock level.
Just because your pool looks clean, doesn’t mean that the algae is gone. This is why we conduct an “Overnight Chlorine Loss Test”. If your pool fails this test, it means there is still sufficient algae present for the water to turn green when your chlorine levels return to normal.
Let me take you through the pool shock process step by step, and explain how to conduct the overnight chlorine loss test.
How to Shock your Pool [in Detail]
As I mentioned before, we will not be using any “shock product”. In my opinion, these really are useless. All they do is increase your chlorine levels, something you can do yourself with the same chlorine you’re already adding to your pool.
To make this process easy to memorize, we will adopt the P-SLAM-T method.
P-SLAM-T is an acronym we will use and it stands for Prepare, Shock Level, and Maintain, Test.
- PREPARE – Prepare
- SHOCK LEVEL – Raise the free chlorine level to “Shock Level”
- AND MAINTAIN – Maintain this free chlorine level for as long as you need to until the pool water is clear.
- TEST – Now, to confirm that the shock has successfully killed all the algae, we will conduct the OCLT (Overnight Chlorine Loss Test).
1. How to Prepare your Pool to be shocked.
Prepare your pool to be shocked by removing all debris from your pool floor, water surface, skimmer baskets, etc. Decomposing plant matter releases phosphates that feed algae and will make killing the algae much more difficult.
You also want to backwash your pool filter. You’ll need it to be running efficiently to filter out all that dead algae.
2. How to raise your free chlorine to “Shock Level”
We are going to use the “triple shock” method by adding 3 pounds of chlorine for every 10,000 gallons of pool water. Allow the chlorine to dilute for an hour or so and test your free chlorine level.
If the free chlorine level is still too low, then simply add another pound for every 10,000 gallons until you reach the desired free chlorine level.
If you can’t get your chlorine levels high no matter how much chlorine you add, your pool might have very high cyanuric acid levels and is experiencing “Chlorine Lock”. The only way to fix this is to change or dilute your pool water.
4. How to maintain the Chlorine “Shock Level”
You want to keep the algae on its backfoot by making sure the chlorine levels are continually high. As the chlorine kills algae, the free chlorine levels will decline. To counter this, you need to test the water a few times throughout the day and add chlorine as necessary.
Add chlorine in increments of 1 pound of chlorine for every 10,000 gallons of water, and repeat if necessary.
You need to maintain this free chlorine level until the water looks clear.
5. How to Conduct an “Overnight Chlorine Loss Test”.
As the name implies, this test needs to be conducted at night. We don’t want to do this test during daylight hours because the sun’s UV rays will neutralize chlorine in the water, and we won’t be able to detect how much chlorine loss is caused by the presence of algae alone.
After the sun is down, test the free chlorine level and write it down. Early in the morning, before sunrise, take another test and calculate how much the free chlorine level has dropped by. If the free chlorine level has dropped by less than 1ppm, then you have successfully completed the pool shock.
If the chlorine loss is more than 1ppm, then there is still algae present in the water and you will want to maintain the “Chlorine Shock Level” for another day and conduct the test again. Repeat this process until the overnight chlorine loss is less than 1ppm.
Did you know? You can sterilize your pool toys and accessories by throwing them into the water during the shock process.
How long do you have to wait to swim after you shock a pool?
This is a valid question. Swimming in a pool with high chlorine levels can be hazardous to your health.
After shocking your pool, wait at least 24 hours from when you last added chlorine or a shock product to your pool. Additionally, you should test the free chlorine level before swimming. The free chlorine level should be between 3 and 5ppm to swim in safely.
Pro Tip! You can speed up the chlorine loss process to shorten this waiting period by making sure the pool is left exposed so that it gets as much sun exposure as possible. The sun’s UV rays will neutralize the excess chlorine.
Some “Shocking” Misconceptions…
When I recently started maintaining my swimming pool myself, I had a lot of questions then that seem odd to me now. With that in mind, I hope I can clear up some of those questions for all the new pool owners.
Can I Add Shock and Algaecide at the Same Time?
The main objective of shocking your pool is to kill algae, so I fully understand why this is such a common question. Many understand that shocking your pool along with algaecide will speed up the process, but in reality, the reverse is true.
You should not add algaecide while shocking your pool. The free chlorine in your water will bind to the algaecide and lower the free chlorine levels in the water, rendering the pool shock treatment ineffective. Always algaecide and pool shock independently.
Can I Add Shock and Chlorine at the Same Time?
This is a question that I come across ALL THE TIME, and is precisely why I said at the beginning of this article that there is a lot of misinformation about “Pool Shock”.
Pool Shock is chlorine. To shock your pool, you actually don’t need to use a pool shock product at all. You can use regular chlorine to get your water to the “shock levels” that you need to shock your pool. If you insist on using a pool shock product, then there is no reason to add chlorine with it.
I highly advise that you just use chlorine. This will save you money, and a trip to the pool supply store.
Is Chlorine and Shock the same thing?
I previously conveyed this a few times in this article, but I just want to go through it again and drive the point home.
Chlorine and Shock is the same thing. Shock is nothing but a highly concentrated dose of chlorine. In fact, you can shock your pool with nothing but regular chlorine. Think of shock as a process to kill algae in your pool, rather than a product.
Conclusion
There is no need to go out and purchase costly shock treatments to get the job done. Shocking your pool can be done with regular chlorine alone and is a remarkably effective way to clear a pool riddled with algae or other microorganisms.
Shocking your pool is simply a process of increasing your pool’s free chlorine levels high enough to kill off any microorganisms in your pool’s water.
The process can take anywhere from 1 to 3 days and depends entirely on how serious your water condition is.
I recently wrote a very helpful article “How Do You Clear a Green Pool Overnight?“, and explained in-depth how to use a modified shock treatment to get your green pool clear in as little as 12 hours. I hope that you find it valuable!