7 Facts On PH Of Deionized Water : Read This First!

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Have you ever wondered about the pH level of different types of water? The pH level measures the concentration of hydrogen ions in a solution, which can affect its properties and uses. One type of water that is often used for testing the pH level of other solutions is deionized water. However, it’s worth noting that tap waters may have varying concentrations of minerals and chemicals that can affect their pH levels. For more accurate results, distillation or adding potassium chloride can help stabilize the pH level of tap waters.

Deionized water, also known as DI water or pure water, is created by removing all ions present in tap water through processes such as reverse osmosis or ion exchange resins. Additionally, it can be produced through the distillation of various waters. This results in a neutral liquid with a pH level close to 7 and free from potassium chloride.

In contrast, tap waters contain various minerals and ions such as potassium chloride that can affect their pH levels. Testing the pH level of these liquids can be challenging due to the presence of other substances. Distillation is a common method used to remove impurities and improve the uses of tap water.

If you’re wondering how to test the pH level of deionized water, it’s typically done using an electrode and comparing it to a standard buffer solution. The normal pH range for deionized water should be around 5-7 depending on factors such as air exposure. Deionized water is produced through distillation or ion exchange to remove enough ions that may affect the pH level. It is different from tap waters which contain various minerals and impurities that can alter the liquid’s pH level.

pH of Deionized Water

Deionized Water

Differences between Distilled and Deionized Water

Distilled water and deionized water are two common types of purified liquid. While they share the goal of removing impurities from tap waters, they have certain properties which distinguish them from each other such as:-

  • Purification Methods
  • pH Levels
  • Usage
  • Cost

Purification Methods Differences between Distilled and Deionized Water

Distilled water is created through the process of distillation, which involves boiling tap water to create steam that is then condensed back into liquid form. This process removes impurities such as minerals, bacteria, and viruses. To ensure its purity, it undergoes a test for ph values, and a ph reading is taken to ensure its quality.

Deionized water is a liquid purified through ion exchange, which removes charged particles from tap waters by exchanging them with resin beads. These beads have an opposite charge to the minerals in the water, allowing them to attract and remove them. The process of deionization results in a neutral ph reading of the final product.

pH Levels Differences between Distilled and Deionized Water

The pH level of distilled water is around 7, which is neutral on the pH scale. On the other hand, the pH level of deionized water can vary depending on the source water and the specific deionization process used. In some cases, it can be slightly acidic or basic. When conducting a test on different types of water, it’s important to note that their pH levels may differ.

Usage Differences between Distilled and Deionized Water

Both distilled and deionized water are commonly used for industrial applications or laboratory experiments where high purity and accurate pH readings are required.

However, distilled water and other types of water are commonly used for drinking and cooking purposes since they have a neutral pH level that makes them safe for human consumption. Many household appliances such as irons or humidifiers require distilled water or other types of water to prevent mineral buildup.

Deionized water is often used in scientific experiments where precise measurements of water are essential since even small amounts of impurities can affect results significantly. It’s also commonly utilized in industries such as pharmaceuticals or electronics manufacturing since these fields require high-purity levels of water.

Cost Differences between Distilled and Deionized Water

When comparing costs between distilled and deionized waters, there are significant differences due to their purification methods. The pH reading can also vary depending on the type of water used.

Distillation and deionization are two common methods used for producing purified water. While distillation is energy-intensive and costly, deionization is a more cost-effective method that requires resin beads and other materials. Both methods result in neutral water, which is safe for drinking and can be used as pure drinking water.

Measuring pH of Deionized Water: Standardization and Limitations

Measuring the pH of deionized water is crucial for various industries, including pharmaceuticals, cosmetics, food and beverage, and electronics. The pH level can affect the quality, safety, and performance of products. However, measuring the pH of deionized waters can be challenging due to their low ion concentration and high resistance to electrical current.

To ensure accurate measurement of pH in deionized waters, standardization is necessary. The use of pH meters and calibration solutions is common in measuring pH of water. These instruments require regular maintenance to ensure their accuracy. Here are some key points to consider when measuring the pH of deionized waters:

Standardization of pH Measurement

Standardizing a pH meter involves calibrating it using buffer solutions with known pH values. This process ensures that the meter provides accurate readings by adjusting it to a known reference point. 

It’s essential to perform this calibration regularly because factors such as temperature changes or electrode contamination can cause drift in readings over time. When testing water, including drinking water, neutral water, and purified water, it is crucial to use a properly calibrated pH meter to obtain accurate results.

Buffer solutions come in different types depending on their intended use and range of measurement. For instance, a buffer solution with a neutral (pH 7) value is suitable for calibrating a meter that measures both acidic and basic solutions. This is particularly useful when testing water quality, including drinking water and purified water.

Use of Calibration Solutions

Calibration solutions are used to adjust the reading on a meter before taking measurements, including those of test water. They come in different strengths depending on the required accuracy level, and using a calibration solution with a higher concentration than what you’re trying to measure may provide more precise results. It’s important to note that calibration solutions should be used with neutral water for optimal accuracy.

It’s essential to follow the manufacturer’s instructions when preparing calibration solutions since they have specific ratios for mixing chemicals with distilled or deionized water.

Limitations in Measuring pH of Deionized Water

Measuring the pH level in deionized water has limitations due to its low ion concentration and high resistance to electrical current flow. Here are some common limitations to consider:

  • Electrode contamination: The electrode is the most critical component of a pH meter. It can be contaminated by oils, dirt, or other substances that affect its accuracy. To prevent this, it’s essential to clean and store the electrode properly after use using neutral water.
  • Temperature changes: Changes in temperature can affect the conductivity of deionized water and cause drift in pH readings. It’s crucial to maintain a consistent temperature when measuring pH levels.
  • Interference from other ions: Other ions present in deionized water can interfere with pH measurements. For instance, carbon dioxide dissolved in water can create carbonic acid and lower the pH level.

Understanding these limitations can help improve accuracy when measuring the pH level of deionized water. It’s essential to follow standard procedures for the calibration and maintenance of instruments used for measuring pH levels.

Understanding pH Measurement for Water: Acids and Alkalies

pH is a measure of the acidity or alkalinity of a liquid, including water. It is an important factor in determining the quality of water for various purposes such as drinking, agriculture, and industrial use. Ion exchange resins can be used to modify the pH of water for specific applications.

The pH Scale

The pH scale ranges from 0 to 14, with 7 being neutral. A reading below 7 means the solution is acidic, while a reading above 7 indicates it is alkaline. The scale is logarithmic, meaning that each unit change represents a tenfold difference in acidity or alkalinity. For example, a solution with a pH of 4 is ten times more acidic than one with a pH of 5.

Obtaining pH Readings

A pH reading can be obtained using a device called a pH electrode. This electrode consists of two parts: the sensing element and the reference element. When these two elements come into contact with the liquid being tested, they generate an electrical signal that corresponds to the hydrogen ion concentration in the solution.

The accuracy of the readings obtained by a pH electrode can be affected by several factors such as temperature changes, the presence of acids or alkalis in the sample solutions among others.

Acids and Alkalies

Acids are substances that donate hydrogen ions (H+) when dissolved in water while bases (alkalies) accept H+ ions when placed in water. The strength of an acid or base depends on how many H+ or OH- ions it releases into solution. Strong acids release more H+ ions than weak ones; strong bases release more OH- ions than weak ones.

When an acid reacts with water it forms hydronium ions (H3O+) which make it acidic while bases react with water to form hydroxide ions (OH-) which make it alkaline. The pH of a solution depends on the concentration of these ions in the solution.

Factors Affecting pH Readings

The presence of acids, alkalies, salts, and organics in the liquid being tested can affect pH readings. Acids and bases react with each other to form neutral substances called salts. Salts can also affect pH readings by releasing enough ions to interfere with electrode measurements.

Organic compounds such as sugars, proteins, and fats can also interfere with pH measurements by reacting with the sensing element or reference element of the electrode. High levels of organic matter in water, along with ion exchange resins, can make it difficult to obtain accurate pH readings.

Maintaining a pH of 7 in Deionized Water: Tips and Tricks

Deionized water, also known as demineralized water, is purified water that has had all ions removed through a process called ion exchange. This process results in water with a neutral pH of 7. However, the pH of deionized water can change due to various factors such as exposure to air, carbon dioxide absorption, and contamination. Therefore, it is essential to maintain a pH of 7 in deionized water to ensure its purity and effectiveness.

Why is the pH of Deionized Water Not 7?

The pH of deionized water is not always 7 because it can easily absorb gases from the surrounding environment such as carbon dioxide (CO2). When CO2 dissolves in deionized water, it forms carbonic acid (H2CO3), which lowers the pH level below 7. Dissolved impurities or contamination can cause changes in the pH level.

Storing Deionized Water

To maintain a pH of 7 in deionized water, proper storage is crucial. Here are some tips for storing deionized water:

  • Store deionized water in clean containers made of glass or plastic.
  • Use containers with tight-fitting lids or caps to prevent exposure to air.
  • Avoid storing containers near sources of pollution or chemicals that could contaminate the water.
  • Keep containers away from direct sunlight or heat sources.

Avoiding Exposure to Air

Exposure to air is one of the main reasons why the pH level of deionized water changes over time. Carbon dioxide from the air can dissolve into the water and lower its pH level. To avoid this problem:

  • Fill your container completely with deionized water so there’s no room for air.
  • Seal your container immediately after filling it with deionized water.
  • If you need to transfer deionized water from one container to another, use a funnel to minimize exposure to air.

Regular Testing and Monitoring

Regular testing and monitoring of the pH level of deionized water is necessary to ensure its purity and effectiveness. Here are some tips for testing and monitoring:

  • Use a pH meter or test strips specifically designed for deionized water.
  • Always calibrate your pH meter before use.
  • Test the pH level regularly, at least once a week or before using the water for any experiments or applications.
  • Keep a logbook of all tests and results.

Measuring pH of Distilled vs Deionized Water: Comparison and Analysis

Measuring the pH levels in water samples is crucial for various industries, including pharmaceuticals, food processing, and manufacturing. The pH level indicates whether a solution is acidic or alkaline, with a value of 7 indicating neutrality.

Distilled Water’s pH Level

Distilled water has a pH level of 7, which means it is neutral. This is because distilled water has no impurities that can affect its acidity or alkalinity. It is produced by boiling water to create steam that is then condensed back into liquid form, leaving behind any contaminants.

Measuring the pH of Distilled Water

To measure the pH of distilled water accurately, you need to use a calibrated digital pH meter. First, rinse the electrode with distilled water to remove any residue from previous measurements. Then fill a clean container with distilled water up to around two-thirds full. Immerse the electrode into the container and wait for it to stabilize before taking your reading.

Deionized Water’s pH Level

Deionized (DI) water has had all its ions removed through an ion exchange process or reverse osmosis filtration system. The resulting product can have varying levels of acidity or alkalinity depending on how it was produced.

Measuring the pH of Deionized Water

Due to its low conductivity, measuring the pH of DI water can be challenging using traditional methods such as litmus paper or colorimetric tests. These methods are not sensitive enough to detect small variations in acidity or alkalinity levels accurately.

Using a digital pH meter is currently considered as the most accurate method for measuring DI water’s pH level due to its high sensitivity and accuracy range. However, when using a digital meter for DI measurements:

  • You need to ensure that the meter is calibrated correctly before use.
  • The electrode needs to be thoroughly cleaned and rinsed with DI water before each measurement.
  • Any samples must be free of any contaminants that could affect the pH readings.

Factors Affecting pH of Water: CO2, Concentration, and Dependence

The pH of water is a measure of its acidity or basicity. It is the negative logarithm of hydrogen ion concentration in moles per liter (pH = -log[H+]). The pH scale ranges from 0 to 14, with 7 being neutral. When the pH is less than 7, it is acidic; when greater than 7, it is basic or alkaline. The pH value has a significant impact on various systems and products that use water.

CO2 in the Atmosphere Can Dissolve in Water and Form Carbonic Acid, Which Affects the pH of Water

Carbon dioxide (CO2) in the atmosphere can dissolve in water and form carbonic acid (H2CO3), which affects the pH of water. The reaction between CO2 and water forms carbonic acid as follows:

CO2 + H2O ⇌ H2CO3

This reaction results in an increase in hydrogen ions (H+) concentration in water, leading to a decrease in its pH level. This process is known as ocean acidification, which can have severe consequences for marine life.

Human activities such as burning fossil fuels increase atmospheric CO2 levels and lead to increased ocean acidification. Furthermore, high levels of dissolved CO2 can also make freshwater sources more acidic.

The concentration of Hydrogen Ions Determines Acidity or Basicity

The concentration of hydrogen ions (H+) determines whether a solution is acidic or basic. Pure deionized water has a neutral pH level because its concentration of hydrogen ions equals that of hydroxide ions (OH-). When an acid dissolves into water, it releases hydrogen ions into the solution, increasing its acidity by lowering its pH value below 7.

On the other hand, when a base dissolves into water, it releases hydroxide ions, which react with hydrogen ions to form water molecules. This reaction decreases the concentration of hydrogen ions and increases the pH value above 7.

Other Factors Affecting pH of Water

Apart from CO2 and concentration, several other factors can affect the pH of water. These include:

  • Temperature: The solubility of gases in water decreases as temperature increases. Thus, warmer water can hold less dissolved CO2, leading to a higher pH level.
  • Minerals in contact with the water: Some minerals such as limestone can increase alkalinity by releasing hydroxide ions into the solution.
  • Chemical reactions with other substances in solution: Chemical reactions between substances in water can lead to an increase or decrease in hydrogen ion concentration, affecting its pH level.

Connection Between pH and Various Systems and Products That Use Water

The pH level has a significant impact on various systems and products that use water. For instance:

  • Aquatic life: Changes in ocean acidity due to increased CO2 levels can have adverse effects on marine life such as shellfish, corals, and plankton.
  • Agriculture: The optimal soil pH for most crops is between 6.0 and 7.0;

Importance of Understanding pH for High-Quality Water

Understanding the pH of deionized water is crucial for ensuring high-quality water. By measuring and maintaining a neutral pH of 7, you can prevent the growth of microorganisms and ensure that your water is safe to use.

Differences between distilled and deionized water should be noted when measuring pH levels. While both types of water are pure, they differ in their chemical composition. It’s important to standardize your pH measurement process to get accurate results.

Acids and alkalies play a significant role in understanding pH measurement for water. You need to understand how these substances affect the pH level of your deionized water so you can maintain a neutral balance.

Maintaining a pH level of 7 in deionized water requires some tips and tricks such as using CO2-free air, avoiding exposure to sunlight, and monitoring concentration levels. These practices will help keep your water at the desired neutral level.

When comparing distilled vs deionized water, it’s essential to measure their respective pH levels. Distilled water has a neutral pH level while deionized water has a slightly acidic one due to its lack of minerals.

Factors affecting the pH level of your deionized water include CO2 concentration, dependence on temperature, and other environmental factors. It’s important to monitor these factors regularly so you can adjust accordingly.


Q: Can I use regular tap water instead of deionized or distilled?

A: No, regular tap water contains impurities that can affect its chemical composition and alter its pH balance.

Q: Can I use pH strips to measure the pH level of my deionized water?

A: Yes, pH strips are a convenient way to measure the pH level of your water. However, they may not provide as accurate results as other methods such as pH meters.

Q: How often should I check the pH level of my deionized water?

A: It’s recommended to check the pH level at least once a week or before each use, especially if you’re using it for sensitive applications.

Q: Can exposure to sunlight affect the pH level of deionized water?

A: Yes, exposure to sunlight can cause a chemical reaction that alters the pH balance of your water. It’s best to store your deionized water in a dark and cool place.

Q: What is the ideal temperature range for maintaining a neutral pH in deionized water?

A: The ideal temperature range is between 20-25°C (68-77°F). Any extreme temperatures can affect its chemical composition and alter its pH balance.


Understanding the importance of maintaining an appropriate pH level in your deionized water is critical for high-quality usage. By following best practices such as standardizing measurements, monitoring concentration levels, and avoiding exposure to sunlight or CO2-rich environments, you can ensure that your deionized water remains safe for use.

About the author

I am Leena Raswant, a chemistry postgraduate. I thrive on challenges and continually specified goals. I aim to learn, unlearn, relearn and spread my knowledge in the best possible ways.