Testing Pool Water

What chemical levels should be tested on a regular basis?

The four main tests to perform with a test kit are pH, chlorine (or other sanitizer residual), Total Alkalinity and Calcium Hardness. Cyanuric Acid levels should be maintained on outdoor pools which use chlorine. Mineral content, Total Dissolved Solids and Acid or Base Demand tests may also be performed as needed.

How often should you test the water?

Ideally everyday, but that may be a bit much for most residential pool owners. Commercial pools are required to check chlorine levels every hour and post their findings in a log, however residential pool owners should check their pH and chlorine levels at least twice per week. Chlorine should be fed continuously through a feeder device to maintain a consistent level. Total Alkalinity and Calcium Hardness levels tend to fluctuate less, so weekly testing should be O.K.

  • pH: 7.2 – 7.8


    Inexpensive chlorine tablets and shock are loaded with stabalizer (conditioner). Over time the stabalizer accumulates creating your chlorine to lock. This means the chlorine is no longer effective, allowing bacteria and algae to grow.

  • Chlorine: 1.0 – 2.0 ppm
  • Total Alkalinity: 80 – 120 ppm
  • Calcium Hardness: 180 – 220 ppm, though some say 200 – 400.
  • Cyanuric Acid: 40 – 80 ppm
  • Total Dissolved Solids: below 5000 ppm

Proper water balance is the single most important factor to maximizing the life and appearance of any swimming pool.


PH Levels

PH is the measurement of acidity of water – measured on a scale of 0 to 14 with 7 being neutral. A pH below 7.0 means the water is very acidic, as the pH approaches 8.0, the water becomes very basic (alkaline).

Not only do proper pH levels allow the other chemicals to do their work, but it is important to note that low and high levels can cause damage to a vinyl liner. Under the right circumstances with pH below 7.0, the liner can actually grow and develop unsightly wrinkles. High pH greatly accelerates the aging process and shortens the life of the liner.

Chlorine is much less effective at higher pH levels. At a pH of 8.0; chlorine is only 22% effective.

Total Alkalinity

Alkalinity is a measurement of the alkaline materials dissolved in water. Alkalinity in the ideal range of 100 to 150ppm helps the pH to resist fluctuations. If the alkalinity is low it can cause a “pH bounce” causing the pH level to fluctuate in and out of the acceptable range.

Calcium Hardness

Calcium Hardness refers to the amount of dissolved minerals in water. A low hardness can lead to corrosion of pool surface, filter, heater, ladder, etc. A calcium hardness level that is too high causes cloudy water and scaling (white chalky appearance).

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