What is the relationship between pH and chlorine?

PSC Ep. 87: What is the relationship between pH and chlorine?

In today’s episode of Poolside Chat, Rob and Matt tackle another common swimming pool question: 
What’s the relationship between pH and chlorine in a swimming pool?

Your pool’s pH level correlates to the effectiveness of the chlorine. If you look at a chart (see chart below)of pH in relation to the chlorine effectiveness, at the top, 6.0 pH level, is going to give you about 90% chlorine effectiveness rate. You don’t want to swim in a pool that’s got a pH of 6.0, it’s too acidic. It can irritate your eyes and skin, etch pool walls, and damage your equipment. On the other side, the flip side, the high pH, your chlorine isn’t effective, but high pH can also lead to cloudy water, it can again irritate your eyes, and cause scale. scale.What is the relationship between pH and chlorine?

The sweet spot for pH would be somewhere between 7.2 and 7.6. If you’ve got low pH, you can add sodium carbonate, soda ash. If you’ve got high pH, you can add muriatic acid to lower it into the proper range.

Again, it’s very important to keep an eye on the pH if you want to have a good chlorine level. That’s would be the relationship, I guess.

If you have any questions about chlorine or pH, please feel free to leave comments down below. For all your swimming pool needs, please visit us over at inyopools.com. Of course, thank you for joining us.


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7 thoughts on “PSC Ep. 87: What is the relationship between pH and chlorine?

  1. Yesterday, we did step 4, after trying all the steps so far. Our water is clear, but we are still getting a reading of TC 1 and FC of 0, all are other readings are in the normal range. We followed your formula for step 4 and, the only difference is we had was that our ph was 7.5 and Step 4 said a high of 7.4. Unfortunately this morning after putting in the amount of calcium hypochlorite calculated, which amounted to 15 bags, our reading was TC 1 and FC 0. Our water is still clear, and we can definitely smell the chlorine. The only thing that has changed in the management of our pool is that we have a whole new pump, filter, skimmer that the manufacturer replaced for us. We also purchased a new testing kit when we kept getting these readings. Both kits are still reading the same. Any suggestions? Thanks in advance for your help.

    1. First, I would check the CYA levels to make sure stabilizer levels are between 30 and 60. Once they are in the right range, try adding the cal-hypo shock at night. Adding the shock at night allows it to work without being depleted by burnoff by the sun.

      1. Hi Matthew,

        Thank you for your response to my posting. Our CYA was and still is 30, and we put the 15 lbs in at night at 11:00 pm and left the filter running. We took the reading of TC 1, FC 0, and CYA 30 at 6 am before the sun was on the pool. Any other suggestions.?

        All the best,


        PS. As suggested in step 2, we replaced 1/2 the water in the pool.

    1. First thought, add chlorine. Check your CYA level, to make sure your CYA is between 30 to 60. When the CYA is in that range, add shock and supplement with chlorine tabs or bleach.

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