Water Chemistry Basics

Though it's not as fun as a pool party, balancing your pool 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 pool water 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 the electric 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.

Total alkalinity is too high: Add Muriatic Acid

Total 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 the pH is also too high. That's ok because it is impossible to adjust the total alkalinity without having some effect on the pH. When you add the muriatic acid to the pool to lower the total alkalinity, the pH will also fall. Often into perfect range.

Alkalinity is to Low: Add Sodium Bicarbonate (aka baking soda, Alkalinity Increaser, Alkalinity Plus)

When you add the sodium bicarbonate to the pool to raise the total alkalinity the pH will also rise.

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, pH Reducer)

Sodium bisulfate is our preferred way to lower pH, as opposed to muriatic acid. It is much safer to store and handle. It is also far easier to dose accurately, vs muriatic. A high pH is a by-product of 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.

If all of this stuff about swimming pool chemistry is too 'sciency' for you. We've got your back. Just head on over to our POOL CHEMISTRY CALCULATOR. We use this tool ourselves. Not that we need it, but it's faster than doing math in your head!


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