Swimming Pool Guides & Reviews by Certified Pool & Spa Operator®
How to Shock a Swimming Pool
When and How to Shock Your Swimming Pool
The Process of Shocking a Swimming Pool
When your swimming pool needs to be shocked, it might make you slightly nervous. This is understandable because a lot of people feel that way, whether they’re experienced or amateur pool owners. It is never comfortable to manage lots of different chemicals. However, once you become more knowledgeable, perhaps you won’t feel so edgy.
First, you need to learn what shocking a pool actually means and why it is done. Once you understand that, you can easily grasp the steps to take for shocking the pool. After you do it a few times, you will get used to it. Then it will seem like no big deal.
You must shock your swimming pool regularly to keep bacteria and algae away from the water. In addition, shocking the pool will help make it smell good.
What does pool shocking mean?
Have you ever passed by a public swimming pool and noticed a strong chemical smell coming from it? If you’re like most people, you probably assumed it was chlorine causing the smell. In reality, the smell is the result of something called chloramines. When there are chloramines present in a pool, it means the water is not being maintained properly.
When people go into a chlorinated swimming pool, they bring their urine, sweat, and oils into the water. These elements mix with the chlorine to create chloramines. As a result, that strong smell is present. But this isn’t the worst of it because your skin could become irritated if it is exposed to these chloramines for too long. Your lungs and eyes may also experience irritation too.
In order to eliminate the abundance of chloramines, you must shock your swimming pool. This simply refers to adding more chlorine to the water to kill the chloramines. A chlorine alternative can also be used instead. This chemical process is known as super chlorination.
About Chlorine in Pools
We will discuss pool shocking in a moment. But first, let’s go over various terms related to chlorine. This will help you understand the process better.
1. Free Chlorine – This is the amount of chlorine in your pool water which is currently disinfecting it. The Free Chlorine level in your pool needs to be anywhere between 1 to 4 ppm (parts per million).
2. Combined Chlorine – This is the chlorine which has already been exhausted in the water. In other words, it is not able to clean the water as efficiently anymore, even though it is still in there. The Combine Chlorine level should be under 0.2 ppm.
3. Total Chlorine – Your Free Chlorine + Combined Chlorine equals your Total Chlorine. To determine the levels of Free Chlorine and Total Chlorine, you need to use a pool water testing kit. The Combined Chlorine can then be learned by subtracting the Free Chlorine from the Total Chlorine.
4. Breakpoint Chlorination – When there is a sufficient supply of Free Chlorine to destroy the Chloramine’s molecular bonds, this is called breakpoint chlorination. To reach this level, you need 10 times the amount of Combined Chlorine.
Whenever you shock your swimming pool, you should attempt to go after the breakpoint. If you don’t reach the breakpoint, then a plethora of chloramines could end up in your pool. As the levels of chloramine increases without being checked, it’ll eventually get so bad that you’ll end up having to replace all the water in the pool.
Pool Shock Types
Ordinary chlorine tablets won’t be enough to shock your pool. There are better chlorine products available which allow you to do this.
Calcium hypochlorite is a classic swimming pool disinfectant which has been used since the year 1928. This chemical is quite cheap to purchase, and it is easy to use for shocking your pool.
• Commercial calcium hypochlorite has anywhere from 65% to 75% chlorine.
• You must dissolve the calcium hypochlorite first and then add it to your swimming pool water.
• Apply the calcium hypochlorite after dusk.
• You cannot swim in the pool for 8 hours once you’ve applied the calcium hypochlorite.
• The calcium hypochlorite adds to the water roughly 0.8 ppm of calcium per 1 ppm of Free Chlorine. Therefore, be careful if there is a lot of calcium in your water.
When there is a high level of calcium in your water, you can spend some extra money on lithium hypochlorite. The chemical dissolves faster than calcium hypochlorite. Because of this, you don’t need to dissolve it first. You can just place it in the water and watch it dissolve immediately.
• There is 35% chlorine in commercial lithium hypochlorite.
• Apply it after dusk.
• You cannot swim in the pool for 8 hours once you’ve applied it.
• Aquatic life can be harmed by lithium hypochlorite. If you need to get rid of the water after it’s been treated recently, take extra special care.
Dichlor is shock chlorine that is simple to use. Some brands of dichlor let you add it to the water directly.
• Dichlor has anywhere from 50% to 60% chlorine.
• It is suitable for shocking the pool and adding standard chlorine doses.
• Most brands don’t require you to dissolve it first.
• Roughly 0.9 ppm of cyanuric acid will be added per 1 ppm of Free Chlorine.
• Use after dusk.
• Wait 8 hours after applying it to the pool.
If you want to swim in the pool soon after you shock it, then try using a non-chlorine shock on the water. Potassium peroxymonosulfate is the main chemical used in non-chlorine shock. It is a cheaper and quicker type of pool shock treatment.
• It doesn’t matter when you add the non-chlorine shock to your swimming pool.
• You only need to wait 15 minutes and then you can swim again.
• Without the chlorine, it has no algaecide function.
The Importance of Night Shocks
Chlorine shocks are usually applied at nighttime because the sunlight will destroy any chlorine that is not stabilized. By doing a nighttime shock, your chlorine will stay strong and do its job.
You need to shock your pool at regular intervals. Don’t just wait until nasty symptoms like eye itchiness and bad odors occur. Shock your pool at least once every 1 to 2 weeks. This will ensure that your water chemistry stays maintained. If you use your pool more often, then it is better to shock it more often too.
Aside from these regular pool shock treatments, there are other times when shock treatments are necessary. Here are some examples:
• Pool parties or any situation where lots of people are in the pool together.
• Huge rainstorms and heavy winds hit the pool area.
• A big change to the water level.
• Feces in the pool
The more shocks you give your pool, the better it will be protected against contaminants like algae and bacteria.
The Procedure for Shocking Your Pool
Now you’re familiar with the chemicals involved. Next, you get to learn the actual steps involved in shocking the pool. Again, do this at nighttime if you’re using a chlorinated shock.
The supplies you’ll need include protective gloves, protective eyewear, long-sleeved shirt, pants, water test strips, closed-toe shoes, pool shock treatment, bucket (5-gallon capacity), and a wooden stick.
Figure out the volume of your pool before you begin (if you don’t currently know). A pool calculator can help you determine the amount of water that your swimming pool can hold.
Steps for Shocking
1. Put your protective accessories on.
2. The pool water needs testing to determine the amount of Free Chlorine, Total Chlorine, and Combined Chlorine. Once you know this, you’ll know the amount of shock to use.
3. Read through the instructions that come with your pool shock treatment. It should have instructions for calculating the amount of shock needed. If you need to do your own calculation, here are the steps involved:
1. The Free Chlorine is subtracted from the Total Chlorine. This gives you the Combined Chlorine.
2. The Combined Chlorine is multiplied by 10.
3. The Free Chlorine is subtracted from this total.
4. Determine how many shock treatment ounces cause a chemical change of 1 ppm in 10,000 water gallons.
5. The pool volume is divided by 10,000 gallons.
6. The chemical change is multiplied by the difference between the Combined Chlorine/Free Chlorine and the divided pool volume.
7. Divide the answer by 16 to convert it into pounds. This is the amount of pool shock treatment needed.
2. If you must first dissolve the shock before putting it into the pool, place warm water into the bucket until it’s filled three-fourths of the way. If you don’t need to dissolve, go to step 4.
3. Pour the shock chemical into the bucket and stir it around slowly. Your objective is to dissolve the chemical. Do this in increments of 1 pound. Go to Step 5.
4. If dissolving the shock treatment was not necessary, figure out the number of shock containers needed. One bag should be added each time. Stop when you’ve made it to your determined breakpoint.
5. The shock should be poured slowly into the water as you circle around the pool on foot. This will ensure it is distributed evenly. If there are solid particles stuck to the bottom of the bucket, lower the bucket into the water and try to dissolve the particles by moving the bucket around.
6. Follow the recommendations of the manufacturer regarding how long you should wait before going into the pool again. That way, you don’t run the risk of experience eye or skin irritation.
Pool maintenance with shock treatments is necessary. However, there are some dangerous chemicals involved in this process. You must handle them carefully, or else it could cause you problems. In fact, if you don’t store your chlorine carefully, it can actually explode.
Protective gear needs to be worn, such as gloves and goggles, if chlorine is being dissolved or handled by you. Pool shock has been known to release traces of chlorine gas, especially the calcium hypochlorite shock. If you want to avoid skin and eye irritation, wear protective gear.
Try not to breathe from the containers because the chlorine gas in there will irritate your lungs and throat. Just keep your face away from the container.
Don’t mix different pool shock treatments together. These are different chemicals and mixing them could result in a huge negative reaction.
Follow the instructions carefully. Don’t dissolve it in the water unless you’re told to do that.
Use 1 container of shock treatment at a time. Wait until the container is empty before opening another one.
If you’ve made it this far, then you’re knowledgeable in pool shocking. The hardest part is the calculations, but they’re not really that bad. Basic math requires just a little bit of thinking, which is good for the brain. Besides, it is worth it because it means your pool will be clean and sanitary for use.