The purity of water is essential in many applications, from pharmaceutical manufacturing and electronics to the proper functioning of your home appliances. But when it comes to purified water, it’s easy to get confused. Is deionized water the same as distilled water?
Many people use the terms interchangeably, but they’re not actually the same thing. So, is DI water the same as distilled water? Short answer: no.
This article will define both distilled and deionized water, explain the key differences between them, and discuss their various uses and safety considerations.
What is distilled water?
Distilled water is water that’s been purified through a process called distillation.
How distillation works
With distillation, the water is boiled, and the steam that results from the boiling is collected and condensed back into liquid water. This process removes impurities that don’t vaporize when water boils.
Distillation removes minerals, most bacteria and viruses, chlorine, and dissolved solids.
Purity of distilled water
Distilled water is considered highly pure, and it’s generally purer than deionized water. Because the boiling process is so effective at removing contaminants, distilled water is often preferred for applications where extremely pure water is needed.
What is deionized water?
Deionized (DI) water has had almost all of its mineral ions removed, usually through a process called ion exchange.
How deionization works
In deionization, the water passes through special ion exchange resins that are designed to attract and bind to dissolved mineral ions. These resins trade the mineral ions for hydrogen and hydroxyl ions, which then combine to form pure water.
What deionization doesn’t do
Although deionization is great at removing mineral ions, it doesn’t remove biological contaminants like bacteria and viruses. If you need water that’s free of both mineral ions and pathogens, you’ll need to use another purification method, such as reverse osmosis (RO). Some systems use a combination of reverse osmosis and deionization (RO+DI) or reverse osmosis and electrodeionization (RO+EDI) to achieve even higher levels of purity.
Key Differences Between Distilled and Deionized Water
While both distilled and deionized water are purified, they get that way through different processes, and that leads to some important differences.
Purification Method
Distillation uses heat to boil water, then collects the steam and condenses it back into liquid form. Deionization, on the other hand, uses ion exchange resins to attract and bind to mineral salts.
Contaminant Removal
Because of the way it’s purified, distilled water is stripped of minerals, bacteria, and viruses. Deionization primarily removes mineral ions, but it may not remove organic contaminants, bacteria, or viruses.
Purity Level
Distilled water is often considered purer, especially when it comes to biological contaminants. Deionized water can achieve extremely high purity when it comes to mineral ions. There are different water purity standards for different applications, from laboratory research to manufacturing.
Cost and Energy
For industrial applications, deionization is often more cost-effective than distillation because it requires less energy.
Conductivity
Distilled water can still conduct electricity because it may contain some ions. Deionized water, because of its lack of ions, has very low conductivity.
What is distilled water used for?
Distilled water is useful in any situation where purity matters. You’ll often find it in laboratories and medical settings, because it’s ideal for experiments and sterilizing equipment.
But you can also use distilled water in your home. Many people use distilled water in:
- CPAP machines
- humidifiers
- steam irons
- lead-acid car batteries
Additionally, some people use distilled water in aquariums and to water houseplants.
What is deionized water used for?
Because of its purity, you’ll often find deionized water used in industrial and scientific settings. DI water is common in the production of:
- Pharmaceuticals
- Cosmetics
- Microelectronics
- Industrial cleaning solutions
In these applications, minerals and other contaminants can damage equipment or affect product quality. Deionized water helps prevent these issues.
Other uses for DI water include cooling systems and some cosmetic products.
Is it safe to drink DI water or distilled water?
Distilled water is generally considered safe to drink. The distillation process removes contaminants, but it also removes beneficial minerals. While safe, long-term consumption of distilled water could lead to mineral deficiencies, since you’re not replenishing those minerals through your water intake. You’d need to get them from food.
Deionized water, on the other hand, isn’t recommended for drinking. Because of its aggressive leaching properties (it’s very pure), it can pull minerals from your body. So, stick to distilled water if you’re looking for purified H2O, but remember it’s not a source of essential minerals.
Final Thoughts
Distilled and deionized water are both purified, but they aren’t the same. Distillation uses heat to boil water and collect the steam, while deionization uses ion exchange resins to remove ions.
Whether you should use distilled or deionized water depends on what you need it for and how pure it needs to be. Before you choose a purification method, carefully consider how you intend to use the water and research the purity levels, costs, and any potential health effects of each option.