Demineralised Water vs. Distilled Water: Understanding the Difference

Water is an essential resource that we rely on for various purposes, ranging from drinking and cooking to industrial processes and scientific experiments. However, not all water is created equal. Demineralised water and distilled water are two terms often used when discussing purified water, but they differ in terms of their purification processes and level of purity.

Demineralised water refers to water that has undergone a process known as demineralisation or deionisation. This process involves the removal of minerals and impurities from water, leaving behind a highly purified form. On the other hand, distilled water is produced through the process of distillation. Distillation involves boiling water, capturing the resulting steam, and condensing it back into liquid form, effectively removing almost all impurities, including minerals, contaminants, and microorganisms.

While both demineralised water and distilled water are highly purified, they serve different purposes due to the variance in their purification processes. Understanding the differences between demineralised water and distilled water is crucial for selecting the appropriate type for specific applications, ensuring optimal performance and desired outcomes. In the following sections, we will delve deeper into the characteristics and applications of each type of water, shedding light on their unique qualities and benefits.

What is Demineralised Water?

Demineralised water, also known as deionised water or demin water, refers to water that has undergone a process of demineralisation or deionisation to remove minerals and impurities. Demineralisation involves the use of various techniques such as ion exchange, reverse osmosis, or deionisation resin beds to eliminate ions, including calcium, magnesium, sodium, and other dissolved minerals from water.

Read more: Deionised Water vs Distilled Water

How is Demineralised Water made?

The process of demineralisation employs various techniques to remove minerals and impurities from water, ensuring a high level of purity. Here are the three common methods used in demineralisation: ion exchange, reverse osmosis, and deionisation.

Ion Exchange

Ion exchange is a widely used method in demineralisation. It involves the exchange of ions in water with ions of the same charge present in an ion exchange resin. The resin typically consists of tiny beads or granules containing ions that are attracted to the target ions in the water. As water passes through the resin bed, the target ions are adsorbed onto the resin, and in exchange, the resin releases an equivalent amount of less problematic ions.

Cation exchange and anion exchange are two types of ion exchange processes used in demineralisation. Cation exchange involves the removal of positively charged ions (such as calcium, magnesium, and sodium), while anion exchange eliminates negatively charged ions (such as chloride, sulfate, and nitrate). By utilising both cation and anion exchange, a comprehensive demineralisation process can be achieved.

Reverse Osmosis

Reverse osmosis (RO) is another effective method employed in the demineralisation process. It utilises a semi-permeable membrane that allows water molecules to pass through while blocking the majority of dissolved minerals, impurities, and contaminants. In reverse osmosis, water is subjected to high pressure, forcing it through the membrane, leaving behind a purified product while the impurities are flushed away.

Reverse osmosis is highly efficient in removing a wide range of contaminants, including minerals, salts, bacteria, and organic compounds. It is commonly used in both residential and industrial settings where high-quality water is required.


Deionisation (DI) is a process that utilises special resin beds to remove dissolved ions from water. It involves both cation and anion exchange resins working together to eliminate charged particles. The cation exchange resin attracts and replaces cations (positively charged ions), while the anion exchange resin captures and substitutes anions (negatively charged ions). As a result, the water passing through the resin beds becomes demineralised and free from most ionic impurities.

What is Demineralised Water used for?

Demineralised water finds widespread application in various industries and settings where the presence of minerals and impurities can interfere with processes, equipment, or desired outcomes. Here are some common uses of demineralised water:


Demineralised water is extensively used in laboratories for a wide range of scientific experiments and analytical procedures. It ensures accurate and reliable results by eliminating the potential interference caused by minerals or impurities present in regular tap water.

Industrial Processes

Many industrial processes require water with a high level of purity to prevent scaling, corrosion, or contamination. Demineralised water is utilised in industries such as pharmaceuticals, food and beverage manufacturing, electronics, power generation, and chemical processing. It is employed in cooling systems, boiler feed water, rinsing and cleaning processes, and as an ingredient in various products.

Car Batteries

Demineralised water is commonly used in car batteries to top up the electrolyte levels. The absence of minerals reduces the risk of impurities interfering with the battery's chemical reactions and prolongs its lifespan.

Steam Generation

Demineralised water is crucial for steam generation in power plants, especially in high-pressure boilers. It prevents mineral deposition and scaling on boiler surfaces, which can reduce efficiency and lead to costly equipment damage.

Medical and Healthcare Applications

Demineralised water is employed in medical and healthcare facilities for procedures that require sterile and pure water. It is used in dialysis machines, medical devices, and as a component in pharmaceutical preparations.

Cosmetics and Personal Care Products

Demineralised water is often used in the formulation of cosmetics, skincare products, and toiletries. Its high purity ensures product stability, consistency, and minimises the risk of adverse reactions on the skin.

Automotive and Aerospace Industries

Demineralised water is utilised in automotive and aerospace industries for vehicle washing, surface preparation, and cooling systems. Its purity helps avoid streaks, residue, and corrosion on delicate surfaces.

Cooling Systems and Heat Exchangers

Demineralised water is used in cooling systems, heat exchangers, and air conditioning units to prevent scaling, corrosion, and clogging caused by mineral deposits. This helps maintain efficiency and prolong the lifespan of the equipment.

What is Distilled Water?

Distilled water is a type of purified water that has undergone the process of distillation. Distillation is a method of separating liquids by utilising their different boiling points. In the case of water, the process involves heating water to its boiling point, capturing the resulting steam, and then condensing it back into liquid form.

How is Distilled Water Made?

The distillation process is a method used to purify water by separating it from impurities through the principles of evaporation and condensation. It involves several steps, including boiling water, capturing steam, and condensing it back into liquid form. Here's a detailed explanation of the distillation process:

Step 1: Boiling Water

The first step of distillation is to heat the water to its boiling point. This is typically done in a container or apparatus called a still. The heat source raises the temperature of the water, causing it to reach its boiling point, which is 100 degrees Celsius (212 degrees Fahrenheit) at sea level.

Step 2: Steam Generation

As the water reaches its boiling point, it starts to vaporise and form steam. The steam consists of water molecules that have broken free from the liquid phase due to the heat energy. The steam contains water vapor along with any volatile compounds or impurities that have a lower boiling point than water.

Step 3: Steam Capture

The next step involves capturing the steam generated during the boiling process. The steam is directed away from the heated water source into a separate chamber or tube, usually through a tube or pipe called a condenser. The purpose is to separate the steam from the liquid water and impurities.

Step 4: Condensation

Once the steam is captured, it undergoes a cooling process to convert it back into a liquid state. The steam is exposed to a cold surface or passed through a series of tubes where it loses heat energy. This cooling causes the steam to condense, meaning the water vapor transforms back into liquid water.

Step 4: Collection of Distilled Water

As the steam condenses, it forms pure distilled water, free from impurities and most dissolved substances. The condensed water is collected in a separate container, often referred to as the receiver or collection vessel. This collected water is the distilled water that has undergone the purification process.

Step 6: Separation of Impurities

During the distillation process, impurities, minerals, chemicals, and other dissolved solids that have a higher boiling point than water are left behind in the original container or still. These impurities do not vaporise along with the water molecules and remain as residue or scale.

Step 7: Repeat Distillation (Optional)

In some cases, multiple distillation cycles may be performed to further enhance the purity of the water. This involves collecting the distilled water from the initial distillation and subjecting it to the distillation process again to remove any remaining traces of impurities.

What is Distilled Water Used For?

Distilled water, due to its high level of purity, finds a wide range of applications in various fields. Here are some common applications of distilled water:

Medical Procedures

Distilled water is extensively used in medical and healthcare settings. It is employed in medical procedures and equipment that require sterile and pure water, such as sterilisation processes, wound irrigation, and in laboratory tests and experiments. Distilled water's purity helps prevent contamination and ensures the safety and effectiveness of medical interventions.

Laboratory and Scientific Experiments

Distilled water is a staple in laboratory settings and scientific experiments. Its purity and consistency make it ideal for preparing reagents, conducting experiments, and calibrating laboratory equipment. Distilled water's lack of impurities ensures accurate and reliable results in various scientific disciplines, such as chemistry, biology, and research studies.

Steam Irons

Steam irons often require distilled water to prevent mineral build-up and clogging. Using distilled water in steam irons helps maintain their functionality and longevity by minimising the accumulation of mineral deposits that can impair steam generation and lead to clogging of the iron's vents.

Automotive Lead-Acid Batteries

Distilled water is commonly used to top up the electrolyte levels in automotive lead-acid batteries. The high purity of distilled water helps prevent impurities and minerals from interfering with the battery's chemical reactions, ensuring optimal battery performance and longevity.

Cosmetics and Skincare Products

Distilled water is a key ingredient in the formulation of cosmetics, skincare products, and toiletries. Its purity and absence of impurities make it suitable for use in products that come into contact with the skin, minimising the risk of irritation or adverse reactions.

Steam Generation and Humidifiers

Distilled water is employed in steam generation systems, such as in power plants and industrial boilers. Its purity helps prevent mineral deposits and scaling on equipment surfaces, ensuring efficient heat transfer and reducing the risk of corrosion. Distilled water is also used in humidifiers to produce clean, bacteria-free steam for maintaining optimal humidity levels in indoor environments.

Calibration of Analytical Instruments

Distilled water is utilised for calibrating various analytical instruments, such as pH meters, spectrophotometers, and conductivity meters. Its known purity serves as a reference point for accurate calibration and ensures the reliability of instrument measurements.

What are the similarities between demineralised and distilled water?

Both demineralised water and distilled water share several similarities and also several key differences. Here’s are the key similarities:

High Purity

Both demineralised water and distilled water undergo rigorous purification processes that result in a high degree of purity. They are free from minerals, salts, impurities, and contaminants present in the original water sources. This high level of purity makes them suitable for applications where the absence of impurities is crucial.

Removal of Minerals

Both demineralised water and distilled water have their mineral content significantly reduced or eliminated. Demineralised water undergoes a process that removes minerals and ions, while distilled water is produced through a distillation process that separates minerals and impurities from the water.

Versatile Applications

Both types of water find diverse applications across various industries and settings. They are commonly used in laboratories, medical procedures, scientific experiments, and industrial processes where high-purity water is required. Additionally, they are utilised in specific applications such as steam generation, car batteries, and the formulation of products that demand water with minimal impurities.

Cleanliness and Sterility

Both demineralised water and distilled water offer a clean and sterile water source. Their purification processes effectively remove bacteria, viruses, and other microorganisms, minimising the risk of contamination in sensitive applications such as medical procedures and laboratory experiments.

Equipment Protection

Both types of water help protect equipment from scaling, corrosion, and other issues caused by mineral deposits. Their low mineral content reduces the likelihood of scaling in pipes, boilers, steam generators, and other equipment, ensuring their efficient operation and longevity.

What are the key Differences Between Demineralised Water and Distilled Water?

While demineralised water and distilled water have many similarities, they also share a couple of key differences. These include:

Impurity Removal

The main difference between demineralised water and distilled water lies in the extent of impurity removal. While demineralised water focuses on the removal of minerals and ions, distilled water goes a step further by removing all impurities, including minerals, bacteria, viruses, chemicals, and other dissolved solids.

Procurement Process

Demineralised water is procured by undergoing processes such as ion exchange, reverse osmosis, or deionisation to target and remove specific minerals like calcium, magnesium, sodium, and other dissolved ions.

On the other hand, distilled water is produced through the process of distillation, which is a more comprehensive purification method. Distillation involves boiling water to create steam, capturing the steam, and then condensing it back into liquid form. 

Can I Use Demineralised Water Instead of Distilled Water?

It is not recommended to use dimeneralised water instead of distilled water. If you’ve been recommended to use distilled water with a piece of equipment, or for medical reasons, we’d suggest erring on the side of caution and using the correct water as instructed. Distilled water is of a much higher purity than demineralised water, and while a bit more expensive, using distilled water will ensure you’re operating a piece of equipment or consuming this type of pure water both the correctly and safe manners.

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