Let’s talk Pool Shock: what is it, really?
“Shock” is a term that is used to describe the sanitization of your pool water by adding chlorine or non-chlorine chemicals in order to do this, one need to raise the “free chlorine” of the water to a point where contaminants are killed. Think getting rid of algae, chloramines or bacteria.
What’s the best pool shock treatment for your pool?
There are 4 main chemical flavors’ of shock, Cal-hypo, Dichlor, Liquid Chlorine (sodium hypochlorite), and MPS (MonoPeroxySulfate which is a Non-chlorine shock) These are chemicals that help sanitize your water or help keep it sanitized when your primary sanitizer dips too low and stays there too long.
This answer depends on why you are shocking and what type of pool you have. Let’s have a look at some:
Cal-hypo is a strong shock that will deal algae a hard blow. You should be aware that it will add calcium to your water and could cause you to experience scaling in salt water pools if the calcium hardness gets too high so you shouldn’t use this if your hardness is already at the top of your desired range.
Liquid chlorine is very effective as a primary sanitizer and as a shock treatment. It is commonly used to clear algae outbreaks because it works quickly and doesn’t need to be dissolved before adding.
Di-chlor is less powerful than cal-hypo, but it can still be used for shocking. It is most commonly used as a weekly maintenance dose to help keep your water clear though. Kind of like an insurance policy against algae.
If you use di-chlor, be careful that you don’t use too much because it contains a stabilizer and you can easily overdose your water. Having too much stabilizer actually inhibits the effectiveness of your chlorine and you will have to dilute your water to reduce the stabilizer levels.
MPS is used as a helper for chlorine.
Its job is to attack organic debris and other contaminants like sunscreen, makeup, and sweat so that your chlorine can focus on microorganisms.
It also helps with reducing chloramines, combined chlorine, so if your water smells like chlorine then MPS can be used to oxidize the contaminants bound to your chlorine and return your water to a healthy state.
Frequently asked questions about pool shocking
What brand should you use and why?
As with any water treatment chemical, you should use a reputable pool brand to be sure that you are getting quality chemical compounds. Local pool and spa stores sell shock that may be branded to their lines or you can also buy from national chains and big box stores.
Can you shock with bleach?
Bleach is nothing more than liquid chlorine, sodium hypochlorite, and you can definitely shock your water with it.
There are a few of things to note about using bleach to shock, or even when using it as a primary sanitizer:
- Chlorine comes in different concentrations and the best to use for maintenance is 12.5%. You can use less concentrated bleach but it will take more and could end up costing you more in the long run.
- You should only use pure sodium hypochlorite and not other mixtures like splashless or scented.
- It’s also best to use liquid after the sun goes down so that it will not be destroyed by the sub before it can do its job. If your water has the appropriate level of stabilizer it will prevent the chlorine from being destroyed as quickly, but it’s best to shock after the sun goes down.
How much shock do I need?
It’s best to follow the manufacturer’s instructions as the amount depends on their mixture and the size of your pool or spa. Before shopping for shock you should make sure that you know how many gallons of water your pool or spa is so you can put the appropriate amount.
If you use Sutro, our app will tell you how much to use depending on the brand of shock and the size of your pool or spa.
How often should I shock my water?
You can shock your water weekly as part of a maintenance routine or just wait until there is a need to shock it. If you maintain your water chemistry there’s almost never a reason to shock unless you find a dead animal in your water or there is a fecal release.
When should I shock my water?
As mentioned previously, it’s best to shock after the sun goes down for the best result. If you are treating a bad algae outbreak you may need to shock over multiple days and that would include doing it during the day to keep your chlorine level high enough to wipe out the algae.
What is needed to shock?
When shocking, or adding any pool chemical you always want to wear eyewear protection, breathing protection, and clothing that covers your skin. If you are using a granular shock then it’s best to dissolve it in a bucket of water before adding it to your water so that it can circulate better and not damage your liner if you have a pool with a liner.
How do I shock a pool?
- Test your water and balance it before shocking so that you start with a good foundation.
- Read the manufacturer instructions and determine how much shock you need and how they recommend adding it.
- Most granular products should be mixed in a bucket of pool or spa water before adding, so do that and pour the shock around the edge of the pool or spa
- Keep the pump running to circulate the water until it is clear.
- If your water isn’t clear the next morning then add more shock and continue the process until it is clear.
How long should I wait before swimming after shocking?
Once again, reference the manufacturing instruction, but it’s common practice to wait 8 hours after using Chlorine-based shock and you should always test the water before getting in to be sure that you aren’t entering too early. A common recommendation is not to swim or bath in water that has a concentration greater than 10 ppm of free chlorine.
If you use non-chlorine based shock, MPS, then you can enter the water after 1 hour.
Why is my water cloudy after shock?
You added shock to make your water clear so why is it that it’s now even more cloudy? Don’t worry, that’s common if you use granular shock. It takes time for it to dissolve, so just keep running your pump until the water clears. If the water doesn’t clear and your chlorine level is below shock level then you should add more shock until the water is clear. You can find more information about clearing cloudy water and treating algae on our website
How does Sutro help with shocking?
This is a great question, and the answer is simple – Sutro Water Monitor can help you avoid the need to shock!
By keeping your sanitizer level in range all the time you shouldn’t need to shock as part of your routine maintenance. And if you do, then Sutro can tell you when your chlorine level is safe to swim after shocking too.