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 are within the recommended ranges. Water balance is crucial for protecting swimmers, equipment, and the pool itself. Water balance 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 necessary 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?

Maintaining water balance is crucial for the protection of swimmers, equipment, and the pool structure itself. This process involves more than just the addition of chemicals. It also requires effective filtration and circulation systems. Filtration is responsible for removing insoluble matter, such as dirt and debris, from the pool. Circulation, on the other hand, ensures that the added chemicals are evenly distributed throughout the pool. If the pump or filter is inadequate or malfunctioning, the quality of the water will inevitably decline. Furthermore, a well-maintained water balance optimizes the use of sanitizers, disinfectants, and oxidizers, enhancing the overall safety and cleanliness of the pool.

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 are 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-, as it follows: lower pH produces more HOBr and higher pH produces more OBr-. pH also determines the levels of HOCl and OCl-. At lower pH levels, more HOCl is produced. HOCl is the most effective form of chlorine for neutralizing bacteria in pool water. Additionally, pH affects the effectiveness of disinfectants and the comfort of swimmers. pH also influences the corrosiveness of the water and the efficiency of sanitizers. Adequate control of pH and total alkalinity has the potential to prevent most water balance problems.

How does Total Alkalinity affect water balance?

Total alkalinity affects water balance by influencing chlorine efficiency and by regulating fluctuations in pH levels. Total alkalinity is crucial for maintaining effective disinfection control and water balance. Low levels cause pH fluctuation, while high levels increase the chance of pH to rise, making it difficult to lower the pH and potentially causing cloudy water. Total alkalinity acts as a pH buffer, preventing drastic fluctuations in pH levels. Total alkalinity 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 decreasing or rising when acidic substances are added to the water.

How does Calcium Hardness affect water balance?

Calcium hardness affects water balance by influencing water’s saturation level. If the water lacks a minimum level of calcium, it will attempt to compensate by dissolving available sources of calcium or magnesium. This leads to the dissolution of plaster pools or metallic parts of equipment. Low calcium hardness leads to difficulty in maintaining water balance, etching of plaster, corrosion of metal components, and eye & skin irritation. On the other hand, high calcium hardness results in 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. This risk is particularly increased when the system contains metals of different types. High TDS also indicate high organic contamination. Furthermore, the addition of chemicals such as sodium hypochlorite raises the water’s TDS, adding sodium and chloride ions to the water. Differentiating between TDS caused by salt or sodium and TDS caused by other, less desirable contaminants is challenging. As a result, it is recommended to lower TDS levels through dilution.

How does Muriatic Acid affect water balance?

Muriatic Acid affects water balance by reducing pH and total alkalinity in water. Adding 35.28 fluid ounces of muriatic acid to a 16,800-gallon pool will lower the pH from 8.0 to 7.5. Muriatic acid is the most commonly used substance for lowering the pH. However, it must be handled with precaution as concentrated muriatic acid severely damages vinyl, fiberglass, or acrylic pools. Before use, muriatic acid must be diluted at a ratio of at least 5:1, preferably 10:1. In the process of dilution, acid is introduced into water, not the other way around.

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. Cyanuric acid protects chlorine from the sun’s ultraviolet rays, acts as a pH buffer, and limits the amount of chlorine available for disinfection and oxidation. Cyanuric acid is typically added once or twice a year in most pools, maintaining a level of 30 to 80 ppm. Levels above 100 ppm lead to complications. Cyanuric acid does not decompose in pool water and is only removed through water replacement or through water displacement, like bathers splashing or exiting the pool. However, cyanuric acid accumulates quickly. When pools contain stabilized chlorine or cyanuric acid, it is necessary to adjust the concentration of free chlorine based on the level of cyanuric acid present.

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. Borate pH buffer helps prevent pH from increasing, particularly when these levels are already high. 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 fluctuations.

How does Temperature affect Water Balance?

Temperature, as a physical factor, affects water balance, especially under extreme conditions like spas with high water temperatures (up to 104°F). The influence of temperature on water chemistry is a crucial aspect of maintaining water balance. For instance, in pools, algae growth is minimal below 65°F, but it significantly increases and becomes more challenging to control above this temperature. High temperatures increase the risk of scaling, while low temperatures 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 has the potential to affect the Oxidation-Reduction Potential (ORP) reading, which is an important parameter in water balance. As the temperature increases, the ORP reading increases correspondingly.

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

Total Alkalinity (TA) must be guided by the pH level, not by the levels of Cyanuric Acid (CYA).
Rather than following wide ranges for water conditions, it is more effective to target specific values.

What is the Saturation Index?

The Saturation Index (SI) is a method used to determine if water will deposit or dissolve calcium carbonate. The saturation index 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 guides decisions about water and chemical additions, and the use of covers. Weather influences water chemistry in various ways. For instance, heavy rainfall amplifies imbalances in pool water chemistry, requiring more frequent adjustments. Sunlight’s ultraviolet rays accelerate chlorine decomposition. Wind, low humidity, and high temperatures increase the speed of evaporation, heightening the need for pool draining. Windborne dirt, leaves, and debris absorb chlorine, effectively reducing its availability in the water. Temperature is another factor that affects water balance, especially under extreme conditions. Wind also accelerates evaporation and carries dirt into the pool, increasing Total Dissolved Solids (TDS) and cleaning requirements.

How Does Rain affect Water Chemistry?

In regions like Southern California, heavy rainfall unbalances pool water chemistry, requiring more frequent adjustments. While the additional water reduces water bills, it complicates the maintenance of chlorine levels and other chemical balances. Rainfall affects water balance and sanitizer demand due to airborne pollutants it carries. Rainfall also benefits plant growth by depositing nitrogen-containing compounds from the air into the soil. This nitrogen, a key ingredient in fertilizer, assists plants in producing 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 are essential in managing these changes.

How Does Sunlight Affect Water Chemistry?

Sunlight’s ultraviolet rays accelerate chlorine decomposition. Without a stabilizer, up to 95% of chlorine becomes degraded in two hours on a sunny day. Sunlight also accelerates algae growth, which affects 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 causes chlorine to decompose rapidly. Without a stabilizer, up to 95% of the chlorine becomes decomposed in just two hours on a sunny day. This has 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 appears as green, brown, yellow, or black slime in pools. Algae affects water chemistry by breaking down bicarbonates, which leads 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. Windborne dirt, leaves, and other debris 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 optimal water chemistry.

How Does Algae Affect Water Chemistry?

Algae affects water chemistry by breaking down bicarbonates, raising pH levels, and increasing alkalinity. Algae growth is accelerated by sunlight and it tends to flourish in areas with less effective water circulation, such as corners and steps. Some algae get removed by brushing, but some remain attached and appear as stains. Removing algae is simpler from smooth surfaces like fiberglass than from rough plaster.

How Does Water Balance Affect Hot Water Facilities?

The balance of water is crucial for hot water facilities as it maintains the Langelier Saturation Index (SI). This index is key to ensuring the effectiveness of disinfectants by maintaining an optimal pH level. Ideal water balance prevents corrosive water from dissolving metal and damaging heating elements. It also protects against scaling conditions, which potentially 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 an optimal total alkalinity. This serves as a buffer against rapid and drastic pH changes, also known as spiking. Different chemicals are 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. pH adjustment 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 supports in achieving 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 the 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, it is necessary to balance the alkalinity, calcium hardness, pH, and total dissolved solids (TDS). It is needed to partially empty the pool and add fresh water that has lower hardness and TDS. Low pH or acidic cleaners effectively remove scale from surfaces.