Basic Pool Chemistry

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Basic Pool Chemistry

Maintaining proper pool chemical balance is essential to keeping a clean and healthy pool. Alkalinity, pH, sanitizer, cyanuric acid (CYA), and calcium hardness are the basic levels to keep in mind when balancing pool water. In particular, the sanitizer level keeps harmful contaminants, like bacteria and algae, out of the pool. In the best words, sanitizers, “sanitize” the pool water. The other chemical levels create an environment for the sanitizer to work effectively and keep swimmers safe. Other specialty chemicals, such as algicides, stain and scale removers and clarifiers, not only, enhance the appearance of the pool, but can help enhance the sanitizer. Algicides help prevent and control algae blooms, stain and scale removers maintain and prevent chemical build up, and clarifiers keep cloudy water clear.

Test Water

Water testing is the first step to pool chemistry. Proper water testing helps “paint a picture” of the chemical makeup in the pool water. Understanding what the chemical balance is helps promote a clean pool and prevent equipment failure. Liquid Test Kits and Test Strips are ways to easily test the basic chemical levels. In addition, professional water testing can be done to more fully understand the chemical levels. Utilizing these tools, regular water testing is essential, testing water at a minimum of once a month. Furthermore, testing the pH and sanitizer levels should be a weekly practice starting before the opening of the pool and the water should be tested when the environment of the pool is impacted. After rainstorms, after large groups use the pool, before algae treatment, changes in weather and adding water, are ways the pool environment is continuously impacted.

Once the water has been tested, adjustments can be made to effect chemical balance. It’s important to test pool water in between chemical adjustments. To understand how to adjust the chemicals, the measures “ppm” (parts per million) and the pH scale are usually used to assess.

Alkalinity Levels

Ideal Alkalinity Level: (80ppm – 150ppm)
Alkalinity levels are important to help maintain the pH balance throughout the pool water. Alkalinity is like a pH buffer, helping prevent pH spikes. When the level is maintained the pH balance becomes easier to control. In addition, alkalinity levels directly affect the pH levels. When the alkalinity levels become too high, the pH will become high as well. This relationship between pH and alkalinity, can cause ineffective sanitizers, scale build up and cloudy water when alkalinity is too high. On the other hand, when alkalinity levels are low, it may cause the pH level to spike since the pH is not properly stabilized.

There are several ways to affect the alkalinity level in a pool. Sodium Bicarbonate (Sodium Bicarb) and Sodium Carbonate (Soda Ash) both increase the alkalinity level. Whereas, Muriatic Acid and Sodium Bisulfate (dry acid) both decrease alkalinity. In addition, draining the pool water and replacing with fresh water will help decrease the alkalinity level.

pH Level

Ideal pH: (7.4 – 7.6)
Managing pH balance in the pool is essential for overall health of the pool and health of swimmer. Imbalanced pH can lead to equipment corrosion, limiting the power of the sanitizer, skin and eye irritation and cloudy water. In addition to the problems it can cause, there are several factors that affect the pH level. Rainwater, algae, increased pool use, pool chemicals and debris can all affect pool pH, so regular testing is needed to keep track of pH level.

Alkalinity helps stabilize the pH level to prevent pH spikes, by properly stabilizing the pH it becomes easier to control. In addition, products like pH Increaser (Up) and pH Decreaser (Down), help adjust pH up or down, respectively.

Sanitizer Level

Sanitizers are meant to keep the pool clean. When the pH is balanced properly the sanitizer can work more effectively. Maintaining proper sanitizer levels differ depending on sanitizer being used. There are several different types of sanitizers that can be used to maintain proper pool health. Regardless of sanitizer used keeping proper chemical balance is needed. When the sanitizer level is low, the pool is not getting cleaned enough. Or when the sanitizer level is high it may cause health risks for the swimmers.


Ideal Chlorine Level: (1ppm -3ppm)
Chlorine is a chemical sanitizer that comes in tablets, granules, or liquid. When chlorine is added to the water hydrochloric acid (HOCI) and hypochlorite ion (OCI) form. Both substances help kill microorganisms, bacteria and other harmful contaminants. Once the HOCI and OCIare finished cleaning, they combine with another chemical or get broken down making the chlorine harmless. Sunlight increases the speed of this process, and more chlorine will have to be added as it breaks down. Cyanuric acid can be added to pool water to help promote chlorine’s power and longevity; however, the cyanuric acid level must be maintained or can have a reverse affect. There are two types of chlorine to keep in mind:

  • Stabilized Chlorine (Trichloro-S- Traizinetrione or “Trichlor”)
    Stabilized chlorine is chlorine combined with cyanuric acid that acts as a stabilizer. The cyanuric acid in the chlorine prevents the available chlorine from being loss due to the sun’s UV rays. However, cyanuric acid builds up over time using stabilized chlorine and this will reduce the chlorine’s effectiveness.
  • Unstabilized Chlorine (Calcium-Hypochlorite or “Cal-Hypo”)
    Unstabilized Chlorine is more venerable to the sun’s ultraviolet rays. Being more vulnerable means the chlorine burns out quicker reducing its effectiveness. So why use it? Unstable chlorine can be used as a pool shock to enhance cleaning power. In addition, it works great for indoor pools where the UV rays less intense. Also, cyanuric acid can be more easily controlled since it is separate from the chlorine unlike stabilized chlorine.


Ideal Bromine Level: (3ppm – 5ppm)
Bromine is a chemical sanitizer that sanitizes through a process called ionization, usually available in tablets or granules. Bromine combines with contaminates and breaks the chemical bond of the contaminates. Unlike chlorine, bromine dissolves slower and stays in the water longer.


Ideal Biguanide Level: (40ppm -50ppm)
Biguanide is a chlorine-free sanitizing liquid. Polyhexamethline biguanide (PHMB) was originally created as a surgical disinfectant. Unlike chlorine and bromine, biguanide does not kill contaminants. Rather it causes them to bind together into insoluble clumps making it easy for the filtration system to remove the contaminants. However, due to the nature of biguanide, its not as effective as chlorine at removing “body-related” pollutants. In addition, the overall effective sanitizing power may dwindle because microorganisms can build a resistance to biguanide.


Ideal Chlorine Level: (0.5ppm)
Minerals are a supplemental sanitizer to chlorine and other sanitizing systems. Minerals like silver and copper enhance the sanitation by acting as a bactericide and algicide. Salt systems use a process called electrolysis to separate the sodium chloride (salt) producing chlorine to sanitize the pool. It simply is a chlorine generator to reduce amount if chlorine needed.

Cyanuric Acid Level

Ideal CYA Level: (40ppm – 50ppm)
Cyanuric acid (CYA) stabilizes (conditions) the pool water, enhancing the effect of chlorine making the chlorine resistant to ultraviolet evaporation caused by the sun. However, when the cyanuric acid levels in the pool get too high it limits the cleaning effect chlorine has. In addition, high amounts of CYA can cause corrosion on pool equipment. Overall cyanuric acid has big impact on pool chemistry. Without CYA, it would cost 5x more to maintain a healthy pool environment.

The optimal cyanuric acid level range is between 40ppm – 50ppm. It’s important to keep the CYA in this range. High CYA levels can lead to cloudy water, green algae growth and higher chemical costs, while low CYA levels allow chlorine to be burned away quicker. Usually, imbalanced levels are caused by stabilized chlorine being used frequently, runoff from plaster in concrete pools or accidentally adding to much. Low cyanuric acid levels are easier to fix, simply add more cyanuric acid to the pool water to increase the level. Unfortunately, when the level is too high, more steps are required to balance.

Calcium Hardness Level

Calcium hardness levels are an important level to keep in mind while balancing pool water. Calcium hardness refers to amount of calcium in the water. Typically, when there is excess calcium in the water, it means there is a bigger chemical imbalance. Proper water testing and chemical adjustment is needed before assessing the calcium hardness. In addition, water temperature directly affects the solubility of calcium in water. When the water temperatures rise it becomes more likely that the calcium will precipitate out.

Imbalanced calcium can lead to potential problems. The ideal range depends on the type of pool.

  • Concrete Pool – the ideal range is between 200ppm – 400ppm
  • Fiberglass Pool – the ideal range is between 150ppm – 250ppm
  • Vinyl Liner Pool – the ideal range is between 150ppm – 250ppm

When the calcium hardness is higher than each respective range it can lead to cloudy water and scale. The cloudy water may not be harmful, but the scale can damage pool equipment. In addition, if the calcium hardness is lower than each respective range it can lead to corrosion. Pool water wants to naturally balance, when the level is low the water will pull the minerals from plaster and/or the metal fitting. Maintain a proper balance to prevent these problems.

Other Chemicals


Sanitizers are the best defense to algae blooms, maintaining a proper sanitizer level prevents algae growth. However, when algae blooms occur, shocking the pool is the best way to eradicate algae. Algicides help prevent algae blooms, but they do not kill the algae. This can be useful when adjusting sanitizer levels and during pool closings. Keeping algae at bay while sanitizer levels are lowers and less effective. Algicides prevent algae with minerals, so if the pool water contains a high level of minerals algicides can stain pool walls and floor.

Clarifiers and Flocculants

Clarifiers help clear up water by improving the effectiveness of the filter. However, the particles that can cause cloudy may not be removed by the filter, leading to the water getting cloudy again. Clarifiers clear the water fast but to prevent cloudy water a flocculant is needed.
Flocculant or “Floc” causes water clouding particles to clump together and sink to the bottom. To get rid of the particles the pool will need to be vacuumed. Floc helps prevent cloudy water by removing these particles once vacuumed.

Metal Sequestrant

Metal sequestrants prevent metals from staining the pool. The sequestrant works by combining with metal particles in the water preventing them from settling on surfaces. In addition, it helps protect plumbing from rust, stain and scale.

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