Can You Over Shock a Pool?

If you’re wondering whether it’s possible to go overboard with shocking your pool, you’ve come to the right place. Shocking your pool is very useful when there are far too many contaminants for a safe swim. Swimming pools can also be cesspools of bacteria and oils shed by other swimmers, so it’s important to keep up with a regular schedule of shocking the pool water now and then.

But can you over shock a pool, and what happens if you do? In this article, I will answer this question and other frequently asked questions regarding pool shock.


Main Takeaways

  • It is possible to over shock your pool, and in the long term, this can hurt your pool plaster and equipment.
  • If you’ve added too much shock to the pool, you can let the sun kill the excess chlorine off or add sodium thiosulfate to the water.
  • While you typically need to add one pound of shock per 10,000 gallons, you might need to add double or triple or, at times, even quadruple the amount if there is an algae infestation.

Can You Over Shock a Pool?

Yes. Pool shock contains a lot of chlorine, and when you shock your pool, you’re already adding an extremely high level of highly concentrated chlorine to your water. Adding double or triple the recommended amount of shock would mean adding an excessive amount of chlorine to your pool.

Usually, adding a bit too much pool shock into your pool is mostly harmless. It’s actually a common tactic called SLAMing your swimming pool. In a day or two, the chlorine will dissipate under strong sunlight, and your pool should be safe to use once again. But that doesn’t mean going overboard with shocking your pool is necessarily a good practice to follow. It does little to speed up the cleaning process and is not healthy for your pool equipment in the long run.

What Happens When You Over Shock a Pool?

Over shocking the pool hurts your water and pool equipment. Chlorine is a very corrosive chemical, primarily when it’s concentrated, and it can wreak havoc on your pool plumbing and plaster.

This is what you can expect if you add too much shock to your pool:

Hazardous Water

If you shock the pool beyond the recommended limits, the water will remain dangerous for swimmers for longer. Swimming in a recently shocked pool is unsafe enough as it is; in a pool with chlorine over 15 ppm (parts per million), there is a chance of someone having a severe medical emergency. For the sake of safety, do not add more shock than needed according to the size of your pool.

Damaged Pool Equipment and Plumbing

At high enough levels, chlorine can eat away at your plumbing, plastic hoses, pool heater, pipes, filters, impeller, igniter, and any other equipment in contact with the water. It could wear the material down completely, which can cause holes to form in important machinery. This is dangerous, not to mention quite costly to repair or replace.

Damaged Pool Plaster, Liner, or Tiling

The lining of your pool, whether plaster, vinyl, or fiberglass, is vulnerable to high chlorine levels. Tiles are sensitive to chlorine as well. Too much shock in your pool could cause your plaster to stain, corrode, become bumpy, stained, or discolored. It is expensive to replace damaged pool plaster, so avoid adding too much if you can.

What To Do If You Put Too Much Shock In A Pool?

If you’re panicking because you’ve accidentally added too much shock, I recommend either of the following steps to lower the level of shock.

Wait It Out

If you live in a sunny area and have added too much pool shock during the daytime, a simple fix is to stand aside and allow the sun’s UV rays to destroy any excess chlorine in your pool. Sunlight is a chlorine killer. The more sunlight your water gets, the faster the chemical levels will reduce. Give it time and space: do not allow anyone to swim in a pool with too much chlorine for at least 48 hours. And always test the water before anyone jumps into the water.

Use Sodium Thiosulfate

Sodium thiosulfate is a rapid chlorine neutralizer. Technically, it eradicates the chlorine element of the chloramines present in your pool. If you are concerned about pool equipment and plaster getting damaged, turn on your pool filter and add half an ounce of sodium thiosulfate per 1,000 gallons of water. Let the pump circulate this for around an hour and test the water soon after. Your chlorine levels ought to be lower.

Can You Under Shock a Pool?

Yes. Much like you can add too much chlorine, it is possible to add too little. Under shocking, your pool does little to nothing to your water. It will remain equally dirty and unclean or low on chlorine levels. To have a balanced approach and avoid either over or under shocking your pool water, it is best to precisely calculate exactly how much shock your pool needs and proceed according to those calculations. 

How To Calculate How Much Shock Is Needed

Follow the steps below to determine how much pool shock your pool needs.

Calculate Pool Volume

The amount of water in rectangular swimming pools can be calculated by multiplying length x width x depth x 7.5. If you have shallow and deep ends in the pool, calculate the average depth: deep end + shallow divided by 2 = average depth. Note this number for the future since you’ll need it for most pool work.

Check out my pool volume calculator if you need more help.

Calculate How Much Shock To Add

Once you know how many gallons of water are in your pool, you need to add one pound of pool shock per 10,000 gallons of water. So if you have a 15,000-gallon pool, you’d need 1.5 pounds of pool shock. Some pool shock comes prepackaged for one-time use for standard-sized pools, so check your local pool store to find something pre-measured to use. Otherwise, it’s relatively simple to measure it yourself using a scale.

To make this calculation more straightforward, I have a ready-made pool shock calculator that you can use. Simply plug in the numbers and let the calculator tell you how much shock you’ll need for your pool!

In The Swim Calcium Hypochlorite Chlorine Granular Pool Shock

In The Swim has a reliable cal hypo shock that is effective and easy to use.

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I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Note On Algae Infestations

If you are dealing with an algae infestation, you would need more shock. Dense algae infestations can eat away a lot of chlorine and remain unaffected. So you might need to double or triple the amount of shock you’ll use depending on the color of your water. For instance, if the water is light green, which indicates an early-stage infestation, add 2 pounds of shock per 10,000 gallons. If dark green, add 3 pounds, and so on. And when it comes to black algae, you will want to quadruple shock your pool.

Get My Free Pool Care Checklist

Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.

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Frequently Asked Questions

How often should you shock your pool?

You should shock the water once a week, depending on how much you use your pool during the pool season. It is also a good idea to shock the pool at the start of the season and the end of it. You should also shock the pool after any major pool party.

How do you shock a pool?

Once you’ve measured the amount of shock needed, place it into a bucket (and mix it with water if you’re using granular shock) and walk around the pool’s perimeter, pouring it slowly into the water for even dispersion. When that’s done, let the pump run, circulate, and filter the water without interruption for 24 hours and test chlorine levels afterward. You can read my article on how to shock a swimming pool for all the steps.

Can you shock your pool after adding baking soda?

Yes, you can. It is safe to add pool shock after baking soda, especially if you wait a few hours in between. Contrary to popular belief, baking soda does not lower chlorine levels. But with that said, since baking soda can make chlorine more effective, you may notice your chlorine levels go down faster.

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