Water Chemistry Basics

Though it's not as fun as a pool party balancing your water should be at least a weekly process and on your mind even more at the beginning of the season and after heavy rains as this is when your water can chemistry can shift. It is true that one of the greatest things about fiberglass pools is that they are LOW maintenance....but that's not the same as 'NO Maintenance'.

If you water is out of balance several things can happen. Some with costly consequences.

  • Damage to pumps - seals fail and allow water to enter motor
  • Damage to salt systems and heaters - corrosion
  • Damage to auto covers - corrosion and fabric degradation
  • Calcium buildup (whitening) on pool surfaces, waterline and accessories
  • Dull or cloudy pool water
  • Clogging of filter elements - Excessive cleaning and poor flow
  • Drop in disinfection potential of chlorine resulting in algae growth
  • Burning eyes and nose
  • Dry, itchy skin and scalp

Below is a cliffs notes version of what to do when.

Alkalinity is too high: Add Muriatic Acid

Alkalinity is the first piece of the water chemistry we must 'balance' before we can effectively manage the rest of the water. In MOST cases when the ALK is too high (or too low) the pH is also too high. That's ok because it is nearly impossible to adjust the ALK without having some effect on the pH. When you add the muriatic acid to the pool to lower the ALK the pH will also fall. Often into perfect range.

Alkalinity is to Low: Add Sodium bicarbonate (aka Alkalinity increaser, ALK plus)

Alkalinity is the first piece of the water chemistry we must 'balance' before we can effectively manage the rest of the water. In MOST cases when the ALK is too low (or too high) the pH is also too low. That's ok because it is nearly impossible to adjust the ALK without having some effect on the pH. When you add the sodium bicarbonate to the pool to raise the ALK the pH will also rise. Often into perfect range.

My pH is too low BUT my alkalinity is OK: Add sodium carbonate (aka Soda Ash, pH up, pH increaser)

There are two ways to increase pH without changing the alkalinity in your pool. The first is to add sodium carbonate. The second is to activate a water feature such as a bubbler or deck jet. By breaking the water's surface and aerating it you will raise the pH naturally. This can take some time and depending on how much you need to increase the pH may not be realistic.

My pH is too high BUT my alkalinity is OK: Add sodium bisulfate (aka dry acid or pH reducer)

Adding sodium bisulfate will lower the pH of the pool without effecting the alkalinity of the pool. A high pH is often caused by salt chlorination systems (electrolysis raises the pH) or by over aeration of the water. If you have a water feature or bubbler jets that run a lot you may simply need to get into the habit of regularly lowering your pH.

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