Water Balance in Pools: All You Need to Know

Water balance refers to the process of maintaining optimal conditions in a body of water, such as a pool or spa, by managing various parameters. These parameters include pH, Total Alkalinity, Calcium Hardness, Temperature, TDS (Total Dissolve Solids), Cyanuric Acid (Conditioner or Stabilizer), and Borate pH buffer. A pool is considered “in balance” when these parameters fall within the recommended ranges. Water balance is crucial for protecting swimmers, equipment, and the pool itself. It involves more than just adding chemicals. Effective filtration and circulation are also necessary. Maintaining water balance also optimizes the use of sanitizers, disinfectants, and oxidizers.

What is balance in chemistry?

In chemistry, balance refers to the state where all components of a system are measured together and the system is neither scaling nor etching. This term is often used in water chemistry, where balance involves measuring components such as pH, total alkalinity, hardness, and temperature. When these components are in balance, the water is considered to be neither scaling (depositing excess minerals) nor etching (dissolving minerals).

What is demand and balance in pool water chemistry?

Demand and balance in pool water chemistry refer to the process of maintaining the right levels of various components in the water. Demand refers to the amount of a certain substance, such as chlorine, that the water requires to reach a predetermined level. Balance, on the other hand, refers to the state where all components of the water (pH, total alkalinity, hardness, and temperature) are neither scaling nor etching. This balance is crucial for protecting swimmers, equipment, and the pool itself. It involves more than just adding chemicals, as effective filtration and circulation are also necessary.

What is the Importance of Water Balance in Pools?

Water balance is crucial for protecting swimmers, equipment, and the pool itself. It involves more than just adding chemicals. Effective filtration and circulation are also necessary. If the pump or filter is inadequate or malfunctioning, water quality will decline. Filtration removes insoluble matter like dirt and debris, while circulation ensures that added chemicals are evenly distributed throughout the pool. Maintaining water balance also optimizes the use of sanitizers, disinfectants, and oxidizers.  Water balance in pools is not just about adding chemicals. It also involves effective filtration and circulation. Filtration is important for removing insoluble matter such as dirt and debris from the pool. On the other hand, circulation ensures that the chemicals added to the pool are evenly distributed. If the pump or filter is not working properly, the quality of the water will decline. Moreover, maintaining water balance is important for optimizing the use of sanitizers, disinfectants, and oxidizers. This is crucial for protecting the swimmers, the equipment, and the pool itself.

What are the Parameters of Water Balance?

The parameters of water balance involve seven factors: pH, Total Alkalinity, Calcium Hardness, Temperature, TDS (Total Dissolve Solids), Cyanuric Acid (Conditioner or Stabilizer), and Borate pH buffer. A pool is considered “in balance” when these parameters fall within the recommended ranges.

How does pH affect water balance?

pH affects water balance by determining the levels of certain chemicals and reactions in the water. It influences the equilibrium of HOBr and OBr-, with lower pH producing more HOBr and higher pH producing more OBr-. pH also determines the levels of HOCl and OCl–, with lower pH producing more HOCl, the most effective form of chlorine for killing bacteria in pool water. Additionally, pH affects the effectiveness of disinfectants and the comfort of swimmers. It can also influence the corrosiveness of the water and the efficiency of sanitizers. Proper pH and total alkalinity control can prevent most water balance problems.

How does Total Alkalinity affect water balance?

Total alkalinity affects water balance by influencing chlorine efficiency and pH changes. It is crucial for proper disinfection control and water balance. Low levels can cause pH bounce, while high levels can cause pH to rise, making it difficult to lower and potentially causing cloudy water. Total alkalinity acts as a pH buffer, preventing the pH from decreasing. It indicates the water’s resistance to pH change and its ability to neutralize acid. Therefore, maintaining a balance in total alkalinity is essential to prevent pH from drifting lower or rising when acidic substances are added to the water.

How does Calcium Hardness affect water balance?

Calcium hardness affects water balance by influencing the saturation level of the water. If the water doesn’t have a minimum amount of calcium, it will attempt to dissolve any source of calcium or magnesium around, often leading to the dissolution of plaster pools or metallic parts of equipment. Low calcium hardness can cause difficulty in balancing water, etching of plaster, corrosion of metal components, and eye & skin irritation. On the other hand, high calcium hardness can cause scale formation on the vessel and in the equipment, cloudy water, eye & skin irritation, difficulty balancing the water, and foaming. Therefore, maintaining the right level of calcium hardness is crucial for water balance.

How does Total Dissolve Solids (TDS) affect water balance?

Total Dissolved Solids (TDS) affect water balance by increasing the risk of galvanic corrosion, especially when there are dissimilar metals within the system. High TDS may also indicate high organic contamination. In addition, the addition of chemicals such as sodium hypochlorite can raise the water’s TDS, adding sodium and chloride ions to the water. This can make it difficult to differentiate between TDS due to salt/sodium and TDS due to less desirable contaminants. Therefore, it is recommended to dilute to lower TDS.

How does Muriatic Acid affect water balance?

How does Cyanuric Acid affect water balance?

Cyanuric Acid, also known as a conditioner or stabilizer, plays a crucial role in maintaining water balance by contributing to the buffering system, influencing total alkalinity, and extending the life of chlorine in water. It protects chlorine from the sun’s ultraviolet rays, acts as a pH buffer, and limits the amount of chlorine available for disinfection and oxidation. It is typically added once or twice a year in most pools, maintaining a level of 30 to 80 ppm. Levels above 100 ppm can be problematic. Cyanuric acid does not decompose in pool water and is only removed through water replacement or when bathers splash and leave the pool. However, it can accumulate quickly, and for pools containing stabilized chlorine or cyanuric acid, the free chlorine concentration needs to be adjusted based on the cyanuric acid concentration.

How does Borate pH buffer affect water balance?

Borate pH buffer affects water balance by resisting changes in pH when acid or alkali are added to the water. It helps prevent pH from increasing, especially at higher pH values. A borate level of 50 ppm is sufficient to buffer the pH from increasing. This buffering action of borate contributes to the overall water balance by stabilizing the pH, preventing significant drifts.

How does Temperature affect Water Balance?

Temperature is a physical factor that affects water balance. It becomes significant under extreme conditions, such as in spas with high water temperatures (up to 104°F).  Temperature influences water chemistry, which is a key component of water balance. For instance, in pools, algae growth is minimal below 65°F but becomes a constant battle above this temperature. High temperatures can increase the risk of scaling, while low temperatures can lead to corrosive conditions. Temperature also affects the Langelier Saturation Index (SI), which is crucial for maintaining water balance in hot water facilities. Furthermore, temperature can affect the Oxidation-Reduction Potential (ORP) reading, which is an important parameter in water balance. As the temperature increases, the ORP reading goes up.

What are the APSP Recommended Ranges?

Condition	Target	APSP Recommended Range
pH	7.5	7.2 to 7.8
Total Alkalinity	90 ppm	60 to 180 ppm
CYA	50 ppm	10 to 100 ppm
Borate	50 ppm	No recommendation
Calcium Hardness (Plaster)	350 ppm	Max 1500 ppm*
Calcium Hardness (Vinyl, etc.)	250 ppm	150 to 1,000 ppm
TDS	1,500 greater than start	Over starting
Temperature	104° F max	No recommendation

Adjust TA to pH, not to compensate for high CYA.
Don’t be misled by ranges for water conditions. Instead, aim for specific targets.

What is the Saturation Index?

The Saturation Index (SI) is a method used to determine if water will deposit or dissolve calcium carbonate. It considers five balance factors: pH, total alkalinity, calcium hardness, temperature, and total dissolved solids.

How Does Weather affect Water Chemistry?

Weather conditions significantly affect water chemistry, especially in pools and spas. Understanding these impacts can guide decisions about water and chemical additions, and the use of covers.  Weather can influence water chemistry in various ways. For instance, heavy rainfall can unbalance pool water chemistry, requiring more frequent adjustments. Sunlight’s ultraviolet rays can accelerate chlorine decomposition, and wind, low humidity, and high temperatures can speed up evaporation, increasing the need for pool draining. Wind-borne dirt, leaves, and debris can absorb chlorine, effectively reducing its availability in the water. Temperature is another factor that affects water balance, especially under extreme conditions. Wind can also accelerate evaporation and carry dirt into the pool, increasing Total Dissolved Solids (TDS) and cleaning requirements.

How Does Rain affect Water Chemistry?

In areas like Southern California, heavy rainfall can unbalance pool water chemistry, requiring more frequent adjustments. While the extra water can reduce water bills, it complicates maintaining chlorine levels and other chemical balances.  Rainfall can affect water balance and sanitizer demand due to airborne pollutants it carries. It also benefits plant growth by bringing nitrogen-containing compounds from the air into the soil. This nitrogen, a major ingredient in fertilizer, helps plants produce chlorophyll, which is green. Algae in recreational waters also use nitrogen in the same way, leading to potential algae blooms in pools after heavy rain. Therefore, weather conditions and bather loads significantly impact water chemistry. Regular testing and adjustments can help manage these changes.

How Does Sunlight Affect Water Chemistry?

Sunlight’s ultraviolet rays accelerate chlorine decomposition. Without a stabilizer, up to 95% of chlorine can be lost in two hours on a sunny day. Sunlight also accelerates algae growth, which can affect water chemistry by breaking down bicarbonates, raising pH levels, and increasing alkalinity.  Sunlight has a significant impact on water chemistry, particularly in relation to chlorine and algae. The ultraviolet rays from the sun can cause chlorine to decompose rapidly, with up to 95% of it being lost in just two hours on a sunny day if there is no stabilizer present. This can have a significant impact on the chemical balance of the water, particularly in pools. Sunlight also promotes the growth of algae, a one-celled plant that can appear as green, brown, yellow, or black slime in pools. Algae can affect water chemistry by breaking down bicarbonates, which can lead to increased pH levels and alkalinity.

How Does Dirt Affect Water Chemistry?

Dirt affects water chemistry by absorbing chlorine, effectively reducing its availability in the water. A dirty pool requires two to three times more chlorine than a clean one to achieve the same results. Therefore, keeping the pool, skimmer basket, strainer basket, and filter clean is crucial.  Wind-borne dirt, leaves, and other debris can significantly impact the chemistry of water, particularly in a pool setting. These materials absorb chlorine, which is a key component in maintaining the cleanliness and safety of pool water. As a result, a pool that is dirty due to these elements requires significantly more chlorine to achieve the same level of cleanliness and safety as a clean pool. This makes the cleanliness of the pool and its associated components, such as the skimmer basket, strainer basket, and filter, extremely important in maintaining proper water chemistry.

How Does Algae Affect Water Chemistry?

Algae can affect water chemistry by breaking down bicarbonates, raising pH levels, and increasing alkalinity. Algae growth is accelerated by sunlight and it thrives in areas of less thorough circulation such as corners and steps. Some algae can be removed by brushing, but some remain attached and appear as stains. Algae removal is easier from smooth surfaces like fiberglass than from rough plaster.

How Does Water Balance Affect Hot Water Facilities?

Water balance affects hot water facilities by maintaining the Langelier Saturation Index (SI), which is crucial for ensuring the disinfectant’s effectiveness by maintaining an ideal pH level. Proper water balance prevents corrosive water from dissolving metal and destroying heating elements. It also protects against scaling conditions that can increase energy costs. Since water balance in spas changes quickly, chemical controllers are beneficial for maintaining proper pH and water balance.

How does adjusting water chemistry affect pH levels?

Adjusting water chemistry affects pH levels by achieving a proper total alkalinity, which serves as a buffer against rapid and drastic pH changes, also known as spiking. Different chemicals can be used to adjust the pH and total alkalinity levels. Acid lowers both pH and total alkalinity, while Soda Ash raises both. Sodium Bicarbonate raises only total alkalinity. Aeration and turbulence raise pH but don’t affect alkalinity. Without any chemicals, total alkalinity lowers but pH remains unchanged. In pools and spas, pH adjustment is crucial for effective maintenance. It involves using different forms of acid to lower high pH levels or alkaline substances to increase low pH levels.

pH and Total Alkalinity Adjusting Chart

This chart helps you achieve a pH of 7.5 and TA of 90 ppm per 10,000 gallons.

pH	20 ppm	30 ppm	40 ppm	50 ppm	60 ppm	70 ppm	80 ppm
6.5	Soda Ash 36 oz	Soda Ash 53 oz	Soda Ash 69 oz	Bicarb 99 oz	Bicarb 51 oz	Bicarb 3 oz	Aerate
6.6	Soda Ash 28 oz	Soda Ash 14 oz	Bicarb 156 oz	Bicarb 135 oz	Bicarb 112 oz	Bicarb 89 oz	Aerate
6.7	Soda Ash 25 oz	Soda Ash 38 oz	Soda Ash 52 oz	Bicarb 117 oz	Bicarb 74 oz	Bicarb 31 oz	Aerate
6.8	Soda Ash 18 oz	Soda Ash 28 oz	Soda Ash 39 oz	Soda Ash 49 oz	Bicarb 128 oz	Bicarb 90 oz	Aerate
6.9	Soda Ash 15 oz	Soda Ash 23 oz	Soda Ash 31 oz	Soda Ash 29 oz	Soda Ash 37 oz	Bicarb 133 oz	Aerate

Note: The chart assumes aeration for TA levels above 80 ppm.

How to Adjust pH and Total Alkalinity to Optimal Levels?

To achieve a pH of 7.5 and total alkalinity (TA) of 90 ppm per 10,000 gallons, follow the chart below. The chart shows the amount of muriatic acid needed and whether aeration is required based on your current pH and TA levels.

Current pH	Current TA (ppm)	Muriatic Acid	Aeration
6.5	320-400	Yes	Yes
6.6	320-400	Yes	Yes
6.7	320-400	Yes	Yes
6.8	320-400	Yes	Yes
6.9	320-400	Yes	Yes
7	320-400	Yes	Yes
7.1	320-400	Yes	Yes
7.2	320-400	Yes	Yes
7.3	320-400	Yes	Yes
7.4	320-400	Yes	Yes
7.5	320-400	Yes	Yes
7.6	320-400	Yes	Yes
7.7	320-400	Yes	Yes
7.8	320-400	Yes	Yes
7.9	320-400	Yes	Yes
8	320-400	Yes	Yes
8.1	320-400	Yes	Yes

The amount of muriatic acid required ranges from 588 to 792 fl oz. Aeration is always necessary after adding the acid.

How to Prevent Scale in Pools?

To prevent scale in pools, balance the alkalinity, calcium hardness, pH, and total dissolved solids (TDS). You may need to drain some pool water and replace it with fresh water that has lower hardness and TDS. Use low pH/acidic cleaners to remove scale from surfaces.