Water will dissolve nearly anything if given enough time. Pool water chemistry involves keeping the water in balance and proper sanitation to prevent the growth of bacteria and algae. Balance means that the water is saturated with minerals and is neither corrosive nor scale forming. If the water lacks the minerals to be in balance, it will try to satisfy the demand by removing the calcium from the pool surface and other metals from the pool equipment. If the water becomes oversaturated, the calcium will precipitate out in the form of calcium carbonate on the pool surfaces.

The number of chemicals related to pool water chemistry overwhelms many new pool and spa owners. This section is designed to give you some basic information regarding pool chemicals, and how they factor into achieving total water balance. Many of the facets of water chemistry, such as calcium hardness, stay at consistent levels once properly adjusted; therefore, our recommendation is to have a water test done at the beginning of the season and throughout the season in order to keep your pool on track.

Before we dive into the chemistry lesson, here are a few helpful reminders to keep your pool water clear all summer long:

Get into a routine. Find a time during the week (like Sunday evening) you're most likely going to be home for on a regular basis. This will help ensure regular water treatment.


Stay ahead of the game. It is important to recognize potential problems and to treat them early. For instance, hot weather depletes oxidizers (shock) and allows for algae growth. When experiencing a particularly hot week in the summer, it makes sense to increase the dosage of shock even when the water appears to be clear.


Chemicals provide balance. People sometimes misunderstand that the primary purpose of adding chemicals to pool water is to create healthy water. Adding chemicals to your water doesn't necessarily create an unhealthy chemical environment, nor does it 'overchemicalize' the water. Instead, chemicals are added in order to accomplish balanced and safe water.

Weather affects water balance and uses up chemicals. Rain, algae, and dust cause pH change and eat up sanitizer. Bather waste and some environmental chemicals have the same effect.

When we talk about water balance, we are measuring the relationship between different factors that decide the overall healthiness of your pool water. The Saturation Index is a mathematical equation that measures the temperature, pH, total alkalinity, and calcium hardness of water in order to predict whether the water is scale forming, neutral or corrosive. All of these factors have a recommended range for pool usage, and it is only when all of these factors are within their prescribed ranges that true water balance can be achieved.

TA is the total amount of alkaline materials (carbonates, bicarbonates, hydroxides) present in the water. TA is a buffer for pH, meaning that it controls the pH's ability to change. TA and pH have a positive relationship with one another. If the total alkalinity is too high, then the pH will most likely remain too high and difficult to adjust. Conversely, if the total alkalinity is too low the pH will stay below respectable ranges and fluctuate excessively. The acceptable range for TA in vinyl, painted, or fiberglass pools is 80-120 ppm. Use Alkalinity Increaser to raise total alkalinity, PH decreaser to lower it. Always have a test done before adding these chemicals.

CH refers to the amount of calcium dissolved in the water. Water that is low in calcium can cause corrosion of pool equipment and surfaces. Water high in calcium has a tendency to form scale; thus, damage to pipes, filtration and heating systems and pool surfaces (vinyl liners) can result. Hard water also depletes chemical effectiveness. The acceptable range for CH in vinyl, painted and fiberglass pools is 175-225 ppm. Raise CH using Calcium Hardness Increaser. When calcium hardness is too high, the only way to lower it is through dilution of water.

Temperature controls the solubility of minerals in the water.

TDS for short; it is the measure of dissolved materials in water. Pools with high solids TDS become more susceptible to cloudiness, and can develop a foul odor. Sanitizer effectiveness can become greatly impeded when TDS is high. Levels should not increase above 2000 ppm.

pH is the measure of the water's acidity or basicity (alkalinity). The pH scale measures from 0 to 14, with 7 being neutral. The numbers on the scale are symbolic representations for an exponential scale (i.e., a pH of 7.2 is 10 times more acidic than 7.4, 100 times more acidic than 7.6, etc.). Low pH causes faster chlorine loss, wrinkling of liners, eye irritation, and chloramine formation (chloramines are byproducts of chlorine after organic waste is consumed, causing pungent smell and skin irritation). Water with high pH is cloudy, scale forming and inhibits chlorine effectiveness. The acceptable range for pH in pools is 7.2-7.6, 7.4 being ideal. Use pH Increaser to raise pH, and pH decreaser to lower it.

*Remember to add such chemicals repeatedly over a long period of time in small quantities so as to reduce pH bounce.

Also known as cyanuric acid, stabilizer acts like sunscreen for chlorine. When maintained around 40 ppm, stabilizer helps reduce chlorine loss by virtue of blocking out the sun's UV rays. CYA remains in pool water unless a significant amount of water is lost, or a drain and refill occurs. While acceptable amounts of this product aid in the sustenance of chlorine, high levels inhibit chlorine effectiveness. Pools using bromine do not require stabilizer.

The most popular forms of pool sanitizer are chlorine and Biquanide. Most often, proper sanitization is the result of using concentrated pucks alongside a regular shocking (also called 'super chlorination') regiment. During hot summer months, one can expect to shock pool water one or two times per week. Heavy usage also dictates how much sanitizer demand your pool will have. One common question is "when is the best time to shock my pool?" The answer simply: at night. On a practical level, you should not use your pool when concentrations of chlorine are high, so it makes sense to shock the pool when no one will be using it. Moreover, the sun's UV rays destroy chlorine. Therefore, if you shock your pool during the day, you will be wasting chemicals.
There are two measurements of chlorine that affect water balance. Free chlorine is the amount of available, unused chlorine present in the water. Combined chlorine refers to the amount of chlorine still present in the water that has combined with organic waste and become inactive. Shocking the water rejuvenates combined chlorine back into usable chlorine. Combined chlorine contains copious amounts of Chloramines, the gas responsible for giving your water "that pool smell." Pool water characterized by poor odor often means that the pool is improperly sanitized, and that it needs to be shocked. Bromine contains similar byproducts called Bromamines, but its odor is less pungent. Some professionals assert that bromine is a better sanitizer because it smells less, but in reality a properly cared-for chlorine pool should never smell either. However, bromine cannot be stabilized against UV degradation.

Algae comes in different textures and colors, with green algae being the most prevalent. It is important to add an initial dosage of algaecide as part of a pool opening treatment, and to add regular weekly maintenance dosages thereafter. Algaecides serve the main purpose of preparing chlorine to battle live algae more effectively.

Certain metals have the ability to permanently damage pool surfaces through staining. The preferred level for metals in pool water is therefore none. Metals commonly found in water are iron and copper and to a lesser extent manganese. Though not a common problem, simple tests can check for their presence. The presence of any one of these metals can create color change on surfaces and in the water itself.