pH Levels and Your Pool Liner

Proper pH levels allow other chemicals to work efficiently, but it is important to note that low and high levels can actually damage swimming pool liners and equipment.

Low pH (Acidic or Aggressive)

Water which is under-saturated will attempt to saturate itself by dissolving everything it comes in contact with, in order to build up its content.  Under the right circumstances with pH below 7.0, the liner can actually grow and develop unsightly wrinkles (Very Important to check your pH prior to closing your pool for the winter to avoid liner wrinkles in the spring).  Low pH in swimming pool water may cause one or more of these problems:

  • Liner wrinkles
  • Corroding of the metal pool accessories (steps, heater .  .  .)
  • Staining, as a result of metal corrosion
  • Rapid dissipation of chlorine, requiring increased dosage
  • Burning eyes and nose; dry and itchy skin and scalp
  • Premature wearing on swimwear, pool toys and accessories

The Remedy – Raise the pH

Adding a base or Bear Alkalinity to the pool water.  If the Total alkalinity is normal, Bear pH increaser should be added according to the instructions on the container.  The active ingredient is sodium carbonate.

Often low pH is a result of acid rain and occurs after periods of heavy precipitation.  The normal tendency of pool water pH is to rise through exposure to wind, sunshine and bathers.

High pH in swimming pool water

High pH greatly accelerates the aging process and shortens the life of the liner.  Water which is over-saturated will attempt to throw off some of its content by precipitating minerals out of solution in the form of scale.   High pH in swimming pool water may result in one or more of the following problems:

  • Accelerated liner aging
  • Scaling or calcium buildup on pool surfaces, waterline and accessories; dull or cloudy pool water
  • Clogging of filter medium or elements
  • Drop in disinfection potential of chlorine, resulting in algae growth
  • Burning eyes and nose; dry, itchy skin and scalp

The Remedy – Lower the pH

Adding an acid to the pool water reduces the pH.  The most common chemicals used to reduce high pool water pH are:

  • Sodium bisulfate – Bear pH decrease is a granule or powder pH reducer, dry acid.
  • Muriatic acid – typically 30% – 35% liquid hydrochloric acid (Dangerous);

If the Total alkalinity of the pool water is within the recommended parameters of 80 – 120 ppm, pH reducer should be added according to the instructions on the container.  The acid should usually be added to water and mixed before treating the pool.  The pump should be running while the acid is slowly distributed around the pool.

How can you tell when your water is over or under saturated?  Use a good test kit (with fresh testing reagents) to measure the chemical parameters of pH, alkalinity, and calcium hardness.


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