Shocking a pool is something that every pool owner will have to do at least once a year. This is done usually when the pool is opened to help clear up the water. Shocking a pool can is how you eliminate algae or rapidly raise the chlorine level of your pool water to combat a green pool. Over time algae, no matter where it is in your pool (even underwater), can stain. When the sun hits dried algae especially, it will cause the algae to stain.
The procedure is called “shocking” because you are introducing an amount of concentrated chlorine powder or liquid into the pool that will immediately start killing bacteria and algae, as opposed to relying on standard chlorine tablets that slowly disintegrate and disperse chlorine over a certain period of time.
Shocking a pool is one of the easier maintenance procedures that can be done to keep your pool clean. Here's how to shock your pool to clean out the green.
Before You Begin
Before beginning any work on your pool, including shocking it, you should inspect the overall condition of your mechanicals and make sure there are no leaks. If there is a leak, no matter how small, the chemicals can escape the pool and cause corrosion. A leak makes it much more difficult to maintain the proper chemical balance your pool needs. Once you have verified your system is water tight, it is safe to begin shocking your pool.
Shock is purely concentrated chlorine in powder or liquid form that starts to dissolve immediately when it contacts something. Just like chlorine tablets, if the shock gets on your clothes there is a good chance that it will bleach them out, and if the shock gets on your skin or eyes it will burn. Before handling chlorine shock or any other chemical, make sure you read the safety precautions on the packaging to familiarize yourself with what to do in case of an emergency. Keep clean water on hand in case the chlorine gets on your skin or eyes.
Equipment / Tools
- Pool Brush
- Extendable pole
- Shock powder or liquid
- Pool test kit (optional)
How to Shock a Pool
Familiarize Yourself With Shock
Each brand of chlorine shock is a little different so be sure to read the packaging thoroughly. Read the instructions, warning, and first aid procedures that are written on your shock packaging.
You can find how much shock to add for your individual pool by usually looking on the back of the shock packet and reading the directions. Generally, if you put a little more than what is recommended it is ok; just be sure to test the chlorine level before swimming again because there is a good chance that the chlorine will be high. It is normal after you shock a pool to have an elevated chlorine level. The elevated chlorine level will return to normal.
Add Chlorine Shock
With all the necessary gear for this procedure nearby, turn your pool on and check that the multiport is set to filter or normal operation. You can then add the shock.
Shock should be added front of the return fitting and around the edge of the pool to make sure that it mixes properly and doesn't concentrate in one area and bleach your pool finish. While adding the chlorine shock, be sure to make it around the pool at least one time to help distribute the shock. Do not add all the shock in one place as it will bleach your vinyl liner or whatever pool finish you have.
Brush the Pool
Brushing the pool after adding shock helps eliminate the risk of bleaching your pool while simultaneously loosening up whatever algae is on your pool's finish (if your pool walls or floor are slippery, that is algae). It is very important to brush the entirety of your pool including the walls, paying careful attention to the water line. If the water line is not scrubbed with the brush, there is a good chance that the line will become permanent.
The best practice is to brush the entire pool walls and floor first, even if it is above the water line, pushing everything towards your skimmer mouth in a continuous motion. Then go back around again and brush the water line. Be as rough as you can with the water while doing this, the idea being to disturb as much of the debris and water as possible so as to dislodge the algae so it floats on top of the water and the filter can pick it up.
If the pool gets cloudy while brushing the pool, that’s actually a good thing. It's a sign that you are loosening up what is causing the problem, and the pool should return to a clear pool within a few days.
Run the Filter
Now that the pool has been shocked and brushed down, the algae and debris will be floating at the top. Leave your pool on (this includes overnight) until the water becomes clear. It is perfectly normal for it to
take a few days (usually 2 to 3 days) of continuous running to allow the filter to remove all of the algae and whatever else was in the pool.
While the pool is running during these few days, it can be helpful to brush your pool daily to pick up what has settled back on the floor.
Be sure to keep an eye on the filter pressure while leaving the pool on. If you notice the PSI is higher than normal, backwash your filters and empty the skimmers baskets for the pool and your pool motor.
When to Call a Professional
After a few days if you notice that your pool is not clearing up and is cloudy or still green, it is best to call a professional. There are some strains of algae that are particularly stubborn that chlorine will not be able to remove or will take an excessively long time to remove and therefore require specialized algaecides to mitigate. Also, this may point to a failing pool filter that is not able to keep your water clean anymore. Both of these issues however can be diagnosed by your local pool technician or sometimes your pool supply store.