Many pool owners new and old wonder how often their pool needs shocking. To shock your pool is by far the best way to remove algae from you pool as well as any other organic matter keeping your pool clean all season long. The downside to shocking is that you restrict the time allowed in the pool as the chlorine levels will be too high to swim in and you need to wait until the chlorine levels reduce to a safe level (3-4 ppm) before it is safe to swim.
So, how often should you shock your pool? The simple answer is as often as it needs it. We will take a deeper dive into this subject below.
What is Shock?
Shock is a chlorine (non-chlorine shocks are available) chemical that is dosed to your pool which will kill any contaminants in your water. The typical chlorine level in a pool should be between 2-3 ppm the aim when you shock a pool is to raise it much higher to over 10ppm which is guaranteed to kill any algae and bacteria that is in your pool water.
The Two Types of Chlorine
There are two types of chlorine we find in a pool. Understanding what they are and how they work is the key to knowing if you pool needs shocking or not.
Free chlorine is what you may typically measure. This is the measurement to determine the proper level of chlorine in your pool water. It shows the amount of chlorine there is available in your pool to kill off bacteria and other pollutants.
Total chlorine is the measurement which shows the chlorine that is free and also the chlorine that has blinded to the pollutants in the pool to kill them.
When you do a test on your pool water the ideal reading would be that the free chlorine and total chlorine are the same number. This would mean that there are no contaminates in your pool and all your chlorine in the water is ready and waiting to do it’s job.
Shocking the pool will drastically increase the level of free chlorine in your pool which will get straight to work on killing any bacteria. Just remember that you will need to wait for the chlorine levels to drop before going swimming again.
Why is Shock So Important?
Shock is an essential chemical in your swimming pool cleaning arsenal. Every time we swim in the pool we introduce contaminates to the water. Sweat, saliva, skin cells, sun tan lotion, urine and other nasties! Adding to this, the environment also adds it’s fair share of dirt, leaves, bugs and not to mention rain which not only affects the pH of your pool but also dilutes the chemicals we have in the pool.
All of the above not only introduce bacteria to a pool they also feed it and therefore we need sanitizers like chlorine to remove them from our pool water to not only kill the bacteria but also to breakdown these contaminants and remove them.
Any time your chlorine levels drop too low, shock your pool and you won’t have to worry about any nasties growing in your pool giving you a safe swimming environment.
How Often Should You Shock Your Pool?
As we mentioned above, the real answer is whenever it needs it however we typically recommend that you should shock once a week or once every two weeks depending on how much you use your pool. Most pool owners will test the pool water twice a week and dose accordingly which may mean that if you are on-top of your maintenance and your pool is on good chemical standing, meaning you may not have to shock as often. If you don’t find the time, then a shock is a good one size fits all precaution to keep bacteria at bay.
The only other times you will want to shock your pool other than your regular weekly of fortnightly shock are:
- After a high bather load (e.g. A party)
- After a heavy rainfall or thunder storm
- After a water change
- At the start and end of the season.
Each of these times, you are best to shock your pool as either the levels of chlorine are likely to be low due to high demand for chlorine or dilution.
As with all things with pool care, make a plan and stick to it. If you use your pool regularly and have a pool in a garden with trees and grass surrounding, we recommend shocking every week.