Water Chemistry is a significant part of the operation of your pool. Maintaining proper water chemistry in your pool will not only ensure the safety of your bathers, but also can increase the longevity of your entire pool system.

There are five chemical parameters that need to be monitored, in addition to the oxidiser used to keep the pool clean and balanced. The oxidiser, or disinfectant, is used to destroy impurities in the water, helping maintain a safe, clean swimming environment. The five chemical parameters all have inverse relationships and all impact the overall water environment in very different ways. It’s important, as a pool operator, that these parameters are carefully monitored, and adjusted when needed, to be kept within the Ontario Health Code requirements, as well as to ensure the adjustments don’t throw the other levels out of range.

pH LEVELS

pH levels and total alkalinity are two chemical parameters who work together and can even be thought of as the best friends of water chemistry. Like most friendships, when treated properly (or balanced in this case), the friendship grows and strengthens, but if one friend is not being considered (pH or total alkalinity), the relationship can become sour quickly.

pH is the single most important parameter in swimming pool water chemistry. It drastically impacts the water balance with even a slight change on the logarithmic scale. As humans, we have a pH of 7.5, so ideally our swimming pools pH level should be maintained within the 7.4-7.6 range. pH is a measure of hydrogen ion concentration in the water, and is measured on a scale of 0-14 with 7 being the neutral pH. 

What Happens when pH Levels are too Low?

When the pH is below 7.2, it is considered to be too low. At this level, the water becomes acidic, and the oxidizer decreases in strength. This will cause eye irritation for bathers, etching of the plaster walls, corroding of metal parts, staining of walls from dissolved minerals, and a significant decrease in alkalinity.

What Happens when pH Levels are too High?

pH is considered to be too high when it reaches 8 and over. High levels of pH can cause your water to become basic, can cause the oxidizer activity to slow and become inefficient, can increase scale formation and discolouration of the pool walls, and can create cloudy water causing your mechanical system to work harder to maintain a clear water environment.

One of the most common operator errors in balancing the pool water is correcting the pH without testing and balancing alkalinity. pH is the most important parameter, and has the largest impact, however, if pH’s best friend, alkalinity, isn’t monitored and balanced, the pH will never be within the proper range.

TOTAL ALKALINITY

Total alkalinity is the measure of a solution’s ability to neutralize hydrogen ions expressed in parts per million (ppm), which is a measure of the water’s resistance to change in pH.  The chemical used to balance alkalinity is Sodium Bicarbonate (baking soda) and the chemical used to decrease alkalinity is an Acid. If the alkalinity is within its required range (80pp-120ppm) it allows the pH to resist change and maintain its level.

What Happens when the Alkalinity Levels are too Low?

When alkalinity levels are too low, getting an accurate pH reading will be impossible Low levels of alkalinity will also create a very acidic pool environment for your bathers. The pH will change rapidly and maintain an acidic environment until the alkalinity is balanced. Once this is complete, the pH can be balanced.

What Happens when the Alkalinity Levels are too High?

If the alkalinity is too high, the pH is not truly reflective of its level and will began to bounce

(7.2,7.8,7.4). Once this occurs, it will throw off all other chemical levels and the water will become an unpleasant environment for bathers. The alkalinity MUST be within its desired range before balancing the pH levels. It is also important to let the alkalinity stabilize before any other levels are touched.

Understanding and monitoring the relationship between these two very important chemical parameters will help decrease issues in the overall chemistry of the pool. It’s important to remember that any time you are adding a specific chemical to the pool, you must be aware of and account for all other chemical levels, including how they will react to one another, and how they will affect the overall comfort and health of your pool water.