How Long to Wait After Shocking a Pool?

Reviewed by Andrada Simion, Master of Science in Chemistry

Shocking your pool is a cleaning method in which excessive amounts of chlorine or other cleaning chemicals are added to the water. Although it is an effective way to occasionally deep clean and remove contaminants, some safety factors should be kept in mind after shocking to help you determine when it is safe to swim again.

What type of chemicals are you using for shocking?

  • If you are using a pool clarifier, wait at least 20 minutes to one hour before swimming.
  • If you are adding calcium chloride, wait for one filtration cycle to pass (typically two to four hours) before entering.
  • If you are using chlorine, it is recommended that you wait a full 24 hours and also test the water levels before it is safe to swim; your free chlorine levels should be stable and match any recommended values on the back of the product, and you should also be able to see the bottom of the pool clearly.
  • If you are shocking with muriatic acid, wait at least 30 minutes to avoid any harmful effects to your skin.
  • If you are adding algaecide, you should wait around fifteen minutes.
  • If you are adding liquid chlorine, wait approximately four hours or until your chlorine levels stabilize at around 5 ppm or lower.

Does your shock contain chlorine?

  • Shocking chemicals are typically separated into categories based on whether they are chlorinated; most shocks that are chlorinated take longer to clean the water than non-chlorine shocks and can alter your pH balance to dangerous levels if you swim too early.
  • If your shock is not chlorinated, it will work faster and be safe to swim at a sooner time – however, it is not as effective of a cleaning agent as chlorine and may be difficult to use on water that is very dirty or contains algal blooms.

How dirty is your pool?

  • The chemical dosage recommended for shocking often depends on how dirty your pool is; although the average swimming pool will usually require three to five times the normal amount of chemicals, an extremely dirty one will require anywhere from five to ten times the normal dosage and result in a longer wait time.
  • If there are algal blooms or other forms of contaminants that are difficult to treat, chemical treatments can even take weeks to complete in order to bring your free chlorine levels back up to a desirable amount; during this treatment time, your pool is not considered safe for swimming.

Other things to keep in mind:

  • A healthy chlorine level in water is typically considered as anywhere between 1-4 ppm; if the concentration measured by your reader is above 5 ppm, you should not enter the water.
  • Even if your chemical levels are safe, do not swim if the water is cloudy – this is a safety hazard that can make it difficult to see submerged swimmers.
  • Shocking your pool should not be a daily routine but instead be used sparingly when a deep cleaning is needed.
  • Many people choose to shock their pools at night to avoid UV damage during the start of the cleaning process; however, choosing to shock your pool at night has no bearing on the amount of time you have to wait before entering the pool and rules should still be followed to determine safety.

Many factors can impact your choice to use certain types of chemicals when shocking your pool. However, whether you are using chlorine or non-chlorinated chemicals, safety should always come first – thinking about the type of chemicals that you’re using and at what level you’re using them will help you ensure that you’re swimming safely.