Category Archives: Pool Water Chemistry

Pool Water Chemistry posts, topics, tips and tricks

The most important part of pool care is balancing your swimming pool. Here we discuss the important parameters for pool water chemistry and how to properly care for your pool.

More Info about Pool Water Chemistry

Why is Pool Water Chemistry so Important?

Everything in a swimming pool is governed by water chemistry. And the chemistry of the pool water is always changing. Algae

Algae’s ability to grow depends largely on the chemistry of the pool. The acidity of the water has a direct relationship with the efficacy of your sanitizer and how quickly it is consumed. Pool Water chemistry includes how much sanitizer is in the water as well as the factors that affect the sanitizer.

Proper chemistry of the pool water ensures that the water is clean and safe to swim in.

What should I test for in my Pool?

There is a wide variety of things that can be checked with a test kit for your pool. Some of these parameters are more important than others.

These are the tests that are considered the most important to pool balancing:

Hardness (total or calcium hardness) PPM

The hardness of the water indicates how much the water has dissolved that could form stains or scale. For example, a high calcium hardness level could lead to scale build up.

Calcium Hardness measures only the amount of calcium in the water. Total Hardness measures calcium hardness and other metals. For this reason, we prefer to test for Total Hardness as it offers a more complete picture.

Hardness is measured in parts per million (PPM).

Total Alkalinity PPM

Total Alkalinity is the most important water parameter. In regards to hardness, it directly influences the likelihood a pool will form stains and scale. The higher the Total Alkalinity the higher the likelihood of stains and scale.

In terms of the pH level, Total Alkalinity influences how easily the pH is likely to change. This is because Total Alkalinity will neutralize acids before they can lower the pH. The higher the Total Alkalinity, the more stable the pH.

Total Alkalinity is also measured in parts per million (PPM)


pH measures the acidity of water. As we mentioned, pH and Alkalinity are directly linked. pH is important because of its impact on sanitizer, surfaces and swimmer comfort.

pH and Surfaces

Too low pH levels can lead to the water dissolving the surface (plaster pools) and corroding metal equipment. Over a long period of time, this can lead to additional staining and equipment failure.

pH and Sanitizer

pH controls how sanitizer behaves in the pool – especially the chlorine level. A low pH will put more of the chlorine into “killing mode” at one time. But this will also cause it to burn off faster. A high pH will reduce or ration the amount of chlorine in “killing mode” but burn off slower.

pH operates on a logarithmic scale with 7 being neutral. This means for every change in pH it becomes 10 times harder.

Sanitizer (Chlorine) PPM

The amount of sanitizer determines how much chemical is available that kills bacteria and algae. The most popular sanitizer for outdoor pools is chlorine.

Free/Available Chlorine

Free chlorine is chlorine that is not combined with another compound. This represents the chlorine available to react to a pathogen to kill it.

Combined Chlorine

Combined chlorine is chlorine that has reacted to something – combining it into a compound. Often this is in the form of chloramines. Chloramines are formed when chlorine reacts to ammonia. Chloramines are not as good a disinfectant and are a skin irritant. This is where pools get they’re “chlorine smell”.

Chloramines are broken up by using large amounts of chlorine shock.

Chlorine compounds are measured in parts per million (PPM).

Why don't other pool chemistry parameters matter as much?

There are many other parameters and compounds that can be tested in pools. Examples include cyanuric acid (cya levels), total dissolved solids (TDS), Oxidation Reduction Potential (ORP), phosphate levels, etc.

However, these are secondary parameters in that they play a much smaller role in pool water chemistry. They are only useful within the context of the primary water parameters. This means they can largely be ignored.

This Simple Fix Will Prevent Most Pool Stains

There is a better way to prevent pool stains – one that does not require purchasing any particular product. It only involves a slight adjustment on how you balance your pool – Jock Hamilton When we are asked to diagnose the reason a pool developed a stain, our first question is always “what’s the alkalinity […]