How Long After Adding Chlorine Can You Test The Water?

How Long After Adding Chlorine Can You Test The Water?

Chlorine is one of the most important swimming pool chemicals because it acts as a sanitising agent preventing bacteria, algae, and other microorganisms from growing in your water.

It’s important to make sure you are getting accurate test readings when measuring your chlorine levels, or else your pool could develop unsanitary conditions.

In this article, we will help ensure that you are getting accurate readings by telling you how long it takes newly added chlorine products to fully mix with your pool’s water.

How Long After Adding Chlorine Can You Test The Water?

The waiting period that you should observe between adding chlorine to your pool and testing your pool’s water can depend on a few factors. Mainly, this amount of time varies depending on what type of chlorine you use.

The following time estimates are calculated by assuming that any added chlorine was properly distributed around the pool according to the product’s instructions and that your pool’s pump system is circulating water during the waiting period.

After Adding Chlorine Granules

Chlorine granules come in a powdered form that can take a while to dissolve. So long as your chlorine granules were spread around the pool upon dosing, it is safe to test your pool’s chlorine levels after allowing this product to circulate through your pool’s water for a minimum of 30 minutes.

After Adding Liquid Chlorine

Liquid chlorine is available in a solution form. This version of chlorine mixes into your pool’s water much more quickly as it does not need time to dissolve. After adding liquid chlorine to your pool, you should wait for a minimum of 15 minutes before testing your water.

After Adding Chlorine Shock Treatment

Although chlorine shock treatments are typically available in a granular form, this product varies when compared to traditional chlorine granules because it is meant to be fast-acting and often involves much larger doses.

Chlorine shock treatments typically cause a rapid rise in chlorine levels, but this spike in chlorine is not designed to last.

To get the most accurate chlorine readings following a chlorine-based shock treatment, test your pool’s levels no sooner than 24 hours after using a shock product.

Although swimming may be allowed much sooner than this, it is important to let your chlorine levels balance out after a shock treatment before determining if you need to add additional maintenance doses of chlorine.

When Using Chlorine Tablets

Chlorine tablets consist of granular chlorine that has been formed into one solid disc shape. These tablets are typically used in skimmer baskets or floating chlorine dispensers.

Because these tablets are designed to be slow-release, you should wait a minimum of 24 hours after adding chlorine tablets to your pool before retesting your pool’s chlorine levels.

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.