When To Shock A Pool

Depending on how hot the week has been and how many people were in the pool will determine how much shock chlorine you’ll be using at the end of the weekend or even at mid-week when your residual testing comes up low, how many times a week you add Shock Chlorine is important, but when you add Shock Chlorine is also just as important. When should you shock your pool?

  • If temperature has been high
  • If usage has been high
  • If free Chl residual is lower than normal
  • If the Combined Chlorine residual goes up 0.5 ppm
  • If there is a smell of chlorine (chloramines) above the pool surface
  • Shock only when Alkalinity (TA) is between 80-120 ppm & pH is 7.2-7.6
  • Sun is down
  • Pool is empty

Most pool owners like myself, learn important lessons after a season or two and that’s to do the maintenance, especially on a bigger Inground pool at night after dark when your pool is empty. The kids are all in bed and a pool owner can get everything done after some good reliable testing. The pool water surface is still and flat which is the best time for using Shock Chlorine. Any agitation in the water will only turn Chlorine into gas and will affect its potency.

Here are some more great tips for Shocking your pool in this article.

How Often Should You Shock Your Pool


There is no set number of times to shock your swimming pool. The pool store guy could tell you 3x a week but it wouldn’t be true. How your pool H2O test out determines how many times a week and how much Shock Chlorine you add including all other contributing factors that come with it. For me that was kids.

I had 5 kids and they had friends lots of them. After all, we had the biggest pool on the block and even had a diving board. After the day is over is the best time to take readings and adjust or add Chemicals. In the “dog days of summer” how many times you shock your pool is according to your pool’s activity and the day’s heat.

It’s a great idea to check a few times more during the Dog Days of Summer when your swimming pool will see heavy usage and high temperatures. This is when a sudden problem might develop. Keep the pool well balanced, especially during this time of the year. Add Shock Chlorine if:

  • If Free residual Chlorine levels come close to zero
  • Combined Chlorine Levels pick up to 0.5 or above
  • If you have to adjust pH (7.2-7.6) then I found it’s a good idea to bump or super chlorinate with Shock Chlorine whether you think you need it or not. 
  • The pool water is showing signs of clouding up

The reason for this is you won’t get a good sanitizing level if the pH is not right and you need to compensate for this until you get the chemistry stabilized and back in business. Don’t let anyone tell you it’s 1-2 or even 3 times a week. The Pool guy’s job is to sell you chemicals when you know as much about your pool or even more than he does. Learn your Pool and Master it. You’ll save money! Use your testing Kit and common sense.

If the August months are hotter than normal that means more people will be in the pool and you will need to test and pay more attention to it, more than you did in July. The chances of you shocking your pool will increase during these periods of time.

Usage and Temperature can make or break a pool. Be the Master of your pool and stay on top of things by controlling the Chemical Balance of the pool’s water. Use a reliable Test Kit and reagents like hit recommended by MyWaterEarth&Sky through Amazon called LaMotte 2064 ColorQ Pro 7 Plus Swimming Pool Water Test Meter Kit


Total Chlorine Higher Than Free Chlorine

How Do You Shock a Pool

Pool Shock costs money and how many bags of shock can increase the cost to operate your pool for the Summer Season? If you are shocking your pool during the day, UV rays from the sunlight will degrade the free chlorine, making the treatment far less potent leaving you back up to the pool store to buy more.

Shocking the pool at night is the best time, also beneficial for any cloudiness to clear up the pool before the kids get started again the next day.

How many people reading this buy Shock Chlorine more than 2x a season? It’s ok-I still do it occasionally-Rarely but occasionally still do. Because in the world of Swimming Pools and I mean any kind of Swimming Pool Inground or Above ground, Fresh or Salt.

Shock Chlorine is a weapon against the dreaded Green monster that threatens to visit you on Monday morning after a long hot weekend. Here’s what you need to know. What they won’t tell you at the Pool Supply Store.

  • Agitation will kill off Chlorine-Adding Shock works better after there is no movement or activity in the pool water. Agitation from the activity in the Swimming Pool will knock Chlorine out of dilution in the pool water rendering it into a Gas form above the water’s level Affecting sanitation.
  • Add Shock Chlorine at Night- Sunlight will ruin Chlorine’s sanitizing effect. You’ll get more Bang for your Buck if you wait until night
  • Remove any skim or toys from the surface of the pool before adding Shock
  • Add water to the pool’s water level to keep movement down at the Skimmers if they are too low you’ll hear the slurping noise that will disturb and add tension to the surface.
  • Let Pool Water Calm Down until no movement
  • Pull the eyelids straight down on the discharges of the filter overnight so there is no surface disturbance
  • Turn off all Water Features and hoses that will cause splashing on the surface. The pool should look flat.
  • Broadcast the Shock Chlorine evenly around and in the deeper ends of the pool. I prefer not to pre-mix. Especially, On a Concrete Pool. Today’s Shock Chlorine is fast-dissolving and unlikely, in a deep pool to do any damage to the bottom.
  • Vacuum and Backwash


How To Remove Algae Stains From Pool Walls



Doing a few things before you add Shock will over the Season end up costing you less on chemicals and I mean any kind of Chemicals. Taking the Organic crap out of the pool will save you money over the season by using more Chlorine. Shocking your pool when the pH is out of perfect range is a waste of money. Take some time at night to get some work done and save money for a change.

Adding Chemicals to your pool should be done on some type of schedule but then there are times because of usage or work that make it impossible. In the event, of a water problem or you are just in a hurry and need to add chemicals, How long does it take for pool chemicals to work?


Read our article on MyWaterEarth&Sky called How Long Does It Take For Pool Chemicals To Work to save money and time for better results. “Be the Master of Your Pool”



 JimGalloway Author/Editor






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