How to ‘Shock’ the Pool

Swimming Pool “Shock”

In the case of a green swimming pool, you are going to need ‘pool shock’. “Shocking” a swimming pool is also a great way to bring things back into balance but should not be over used.

Is it necessary to shock a pool?

The simple answer is, yes. The reason why shocking a swimming pool is beneficial is due to the amount of available chlorine diminishes over time, much like the work implies to ‘shock’ the swimming pool means that you surge the amount of chlorine in the pool past the ‘break-point’ killing off any and all bacteria, but also resulting in chlorine levels rapidly depleting down to zero.

This sudden spike in extreme chlorine levels is why it is never advised to swim in a pool that has been shocked within the last 24 hrs.

The main reason for shocking the pool is to kill off excessive bacteria that can thrive in normal chlorine conditions to help keep pool water fresh and healthy.

How to ‘shock’ the swimming pool

Before dumping bags of shock into the pool here are a few tips to adding shock to a swimming pool:

  • Make sure the pool is running
  • First: check and adjust your pool pH level to 7.2
  • Get a bucket and mix the shock with water first
  • Wear clothes you don’t care if they are bleach stained
  • Make sure to brush completely after adding in the pool
  • If possible also run the pool cleaner for added circulation

Pour the shock and water mixture into the pool following the perimeter, don’t forget to brush until it is dissolved, and use the pool cleaner if possible.

Best time of day to shock a swimming pool: in the evening or at night

Note: 24 – 48 hrs after shocking the pool the residual chlorine levels will plummet, so take note of your pool stabilized level, and make sure that you have chlorine tablets in your pool system.

Related: DIY Swimming Pool Maintenance 101

Amount of shock to add to a pool

Under normal conditions (meaning, a clear pool) you would only want to shock your pool once every 2 months or so. If you have a green pool or just had a bad rain storm that diluted the pool water you may need to ‘shock’ or also called ‘super-chlorinate’ the pool.

Normal pool shock amount:

1 lb per every 10,000 gallons of pool
Example: a 15,000 gallon pool requires 1.5lbs to 2lbs of pool shock

Green pool shock amount:

3lbs per every 10,000 gallons of pool

Need help figuring out your swimming pool water capacity? GO TO: Pool Water Calculator

How long it takes to shock a pool

The shock takes action immediately inside the pool, and it may turn the water a milky white for a short time before causing the water to become crystal blue. The amount of time for shocking a pool, and for those to wait before swimming, is typically 24 – 48 hrs, or when the available chlorine levels are back to within the 2.5ppm to 3.5ppm range.

Run the pool: During the first 24hrs of shocking a pool you should run the pool equipment continuously, then back on a timer.

Note: It is advised to allow your pool to re gain residual chlorine before allowing bathers to resume swimming, this may take longer than the 48 hrs and depends on the efficiency of your pool system. This way you will not have a green pool all of the sudden when you wake up after having a pool party asking yourself why when you had just shocked the pool!

Helpful fact: 1 Dog in a swimming pool is equivalent to 40 human bathers, think about that next time you let those dogs out.

how to shock a green swimming pool

Shocking the pool in the rain

If you need to shock the pool while raining chances are you have a green pool and need to take some immediate action. YES, you can shock a swimming pool in the rain, just follow the tips we mentioned above.

How to shock a salt water pool

A salt water pool will need a bit of a ‘chlorine refresh’ just like a chlorine pool. The methods are the same for using granular pool shock, but there is also an option to “boost” or “super chlorinate” from your salt system controller that will increase chlorine output to 100% for 24hrs or longer.

What happens when you swim in a shocked pool

For pools that have added 1lb per 10,000 gallons and a person swims within 24hrs the bather would become very uncomfortable very quickly. It will cause the eyes to burn and the skin to feel dry, and after getting out will smell chlorine for a while.

For people who swim in a pool that has over 3lbs per 10,000 gallons within the first 48 hrs may experience the same discomforts from above but may be more intense.

In either case an accidental swim in a shocked pool is not life threatening for humans or pets, but extended periods of time may pose a real health risk.

Understanding Swimming Pool Chlorine

Chlorine in swimming pools is looked at in 3 ways:

  • Free (available) Chlorine = the level of available chlorine to fight bacteria and keep water clear
  • Combined (residual) Chlorine = this is the actual “chlorine smell” when bacteria begins to overcome the free chlorine
  • Total chlorine = combines both available + residual for total chlorine in the pool

You’ll enjoy the pleasures of swimming in crystal clear pool water by regularly maintaining and shocking your pool, typically every 2 – 3 months in normal conditions.


Still have questions? Talk to the chemists at PoolSupplyWorld.com!

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