Pool Chlorine Level NOT Registering after Shock

Is your pool chlorine level NOT registering after shock? If your free chlorine levels PPM (Parts Per Million), are not rising with your test strips after extensive shocking, you're not alone. This is a common problem that many pool owners face at some point in time. Usually early on and within the first year of ownership.

Why is my Pool Chlorine Level Not Registering?

pool chlorine level not registering after shock You would not believe how many new pool owners think that they simply need to shock and vacuum a pool to keep it maintained throughout the season (I used to be one of them). In reality there are many other factors that come into play to help you maintain clean, safe, and sparkly water.

For example, if your chlorine level is not registering on your test strips after multiple shock attempts, the number one reason is most likely that your pool needs a conditioner or stabilizer that contains Cyanuric Acid. Without this conditioner or stabilizer, water will lose chlorine very quickly to the sun. A pool with no cyanuric acid can lose all of its chlorine within just two hours. Cyanuric Acid works much like Sunblock does to protect our skin from damaging UV rays. However, in the case of a pool, this stabilizer keeps the UV rays from breaking down the chlorine.

Steps to raising a low pool chlorine level

The following simple steps should be performed when a pool has been shocked but the chlorine level never rises. Or when the chlorine level doesn't remain stable for more than a couple of days.

  1. First, you will need to test your cyanuric acid level using either CYA test strips or for better accuracy a digital CYA test kit.
  2. Next, assuming the cyanuric acid in pool is low, add a pool conditioner until reaching the ideal range (30-50PPM).
  3. Then, test your chlorine level after the cyanuric acid has been dispensed and is well circulated. You will likely notice chlorine suddenly registering on the test strip. In fact, the chlorine level might even register a bit high, and you won't need to add any more.
  4. Finally, continue to test your cyanuric acid level once a month throughout the season to keep the PH level balanced.

Notes: If you are using dichlor or trichlor as your primary chlorine sanitizer, you are already introducing cyanuric acid along with the chlorine and may be experiencing another problem.

Lowering cyanuric acid in swimming pools

If you find the cyanuric acid level is too high, you can reduce or lower cyanuric acid in the pool by replacing a portion of your existing water with fresh water. To determine how much water to replace, simply subtract your desired level from the current reading and then divide the result by the current reading. For example, let's calculate how much water you'd need to replace to lower the cyanuric acid (CYA) level from 80 ppm to 40 ppm.

  • Current cyanuric acid level: 80 ppm
  • Desired cyanuric acid level: 40 ppm

Calculate amount of water to be replaced to lower Cyanuric Acid Level

  1. First find the difference between the desired and current levels:
    80 ppm (current) - 40 ppm (desired) = 40 ppm (difference)
  2. Then, divide the difference by the current concentration level:(40 ppm / 80 ppm) * 100% = Replace 50%

So, in this example, you would replace approximately 50% of your pool's current water with fresh water to lower the cyanuric acid level from 80 ppm to 40 ppm. This means half of the water in your pool should be replaced with fresh water to achieve your desired CYA level.