Is Distilled Water Good for a Long Time?

January 13, 2026 •

4 min read

According to water experts, commercially bottled distilled water can last indefinitely if kept in a sealed container, as the distillation process removes minerals and impurities that cause degradation. This longevity, however, hinges entirely on proper storage to prevent contamination once the seal is broken. So, is distilled water good for a long time? The answer depends on your handling.

Quick Summary

An unopened bottle of distilled water can last indefinitely with proper storage, but its purity is compromised within weeks once opened due to potential exposure to contaminants. Long-term storage depends on container material, handling, and environmental factors.

Key Points

Indefinite Shelf Life (Unopened): Distilled water, if properly sealed in a food-grade container and stored away from contaminants, can last indefinitely.
High Contamination Risk (Opened): Once opened, its purity is easily compromised by airborne microbes, making it susceptible to contamination within weeks.
Essential for Appliances: Its mineral-free nature is ideal for devices like CPAP machines and steam irons, preventing mineral buildup.
Potential Health Risks with Long-Term Drinking: Exclusive, long-term consumption of distilled water can potentially lead to mineral deficiencies, though this is rare with a balanced diet.
Proper Storage is Crucial: Store in a cool, dark place using clean, airtight glass or HDPE containers to preserve purity and prevent contamination.
Not Sterile: Distilled water is not the same as sterile water and is not suitable for all medical uses, especially injections or wound care, without further sterilization.

The Science Behind Distilled Water's Shelf Life

Distilled water is created through the process of distillation, which involves boiling water and collecting the resulting steam as it condenses back into a liquid. This purification method leaves behind dissolved minerals, contaminants, bacteria, and viruses. The exceptional purity of this H2O is the primary reason for its potential to last a very long time, as there are no organic or inorganic materials left to support microbial growth or cause spoilage.

However, this very purity is also its weakness. The moment a container is opened, the water becomes susceptible to absorbing contaminants from its surroundings, including airborne microorganisms, container materials, and chemical fumes. This is why proper storage is crucial for maintaining its quality, especially for specific applications like medical devices or sensitive lab work.

Factors Affecting Distilled Water's Longevity

Storage Conditions

Cool, Dark Place: Storing distilled water in a cool, dark location away from direct sunlight is essential. Heat and UV light can degrade plastic containers over time, potentially leaching chemicals into the water.
Sealed Containers: An airtight, sealed container is the most important factor for long-term storage. Once opened, the exposure to air can introduce microorganisms and affect the water's purity.
Container Material: The type of container matters significantly. For long-term storage, high-density polyethylene (HDPE) food-grade containers or glass bottles are recommended. Amber glass, in particular, can block UV light. Avoid storing distilled water in cheap, thin plastics or containers that previously held anything else, like old milk jugs, as they can be difficult to clean and sanitize completely.

Uses and Potential Contamination

Distilled water's shelf life changes dramatically depending on its intended use and whether the container has been opened. For medical purposes, such as CPAP machines or nebulizers, opened distilled water should be used within a week to ensure hygiene. For general household tasks, it may last a few weeks. For automotive applications, it can last longer, but vigilance is still necessary. Always ensure any device using distilled water is cleaned regularly according to the manufacturer's instructions to prevent contamination.

Comparing Distilled Water to Other Water Types

To understand the unique shelf-life properties of distilled water, it's helpful to compare it to other common water types.


Feature	Distilled Water	Purified Water	Tap Water
Purity	Highest purity; nearly 100% H2O.	High purity; meets strict standards (e.g., <10 ppm TDS).	Varies widely; contains minerals, chlorine, and trace contaminants.
Mineral Content	Virtually mineral-free.	Typically has some minerals added back or left in.	Contains naturally occurring minerals.
Taste	Flat or bland due to lack of minerals.	Taste can be improved with added minerals.	Taste varies based on source and treatment.
Opened Shelf Life	Compromised within 1–4 weeks due to contamination risk.	Varies, but still prone to contamination once opened.	Safe for a day or two after opening and refrigeration.
Primary Use	Appliances, labs, medical devices.	Drinking and general consumption.	Drinking, cooking, cleaning.

Long-Term Drinking Considerations

While is distilled water good for a long time in storage, drinking it exclusively for extended periods is a different matter. Distilled water's lack of essential minerals like calcium and magnesium can potentially lead to deficiencies over time, especially if a person's diet is lacking. The World Health Organization has noted that exclusive consumption of demineralized water may be linked to certain health risks, though it's important to note that most people get their minerals from food, not water. For most healthy individuals with a balanced diet, occasional consumption is not an issue. Those with specific health conditions or who are poorly nourished should consult a healthcare professional before making it their primary drinking source.

Signs of Contaminated Distilled Water

Even when stored properly, it's wise to check for signs of contamination, especially if the container has been opened for a while. Indications that the water may have gone bad include:

Cloudiness or visible particles: The water, which should be crystal clear, appears hazy or has suspended matter.
Unusual odors: A chemical or moldy smell is a clear sign of contamination.
Algae growth: Any sign of green or brown growth inside the container means it is compromised.
Off-taste: A strange or plastic-like taste suggests contaminants have leached into the water.

Conclusion

To answer the question, is distilled water good for a long time, the consensus is yes—if it remains properly sealed and stored. Unopened, a bottle of distilled water can last indefinitely. However, its exceptional purity makes it highly susceptible to contamination once the seal is broken. The duration of its safety post-opening depends heavily on the storage environment and its intended application. For optimal and safe use, adhere to careful handling procedures and store it in clean, sealed, food-grade containers in a cool, dark place. For long-term emergency drinking water, it's vital to rotate your supply regularly and inspect for any signs of contamination before use.

Frequently Asked Questions

While generally safe for short-term consumption, drinking distilled water exclusively for a long time is not recommended. It lacks essential minerals like calcium and magnesium, which can potentially lead to deficiencies over extended periods if not compensated for in a balanced diet.

The water itself does not expire in the traditional sense because it lacks impurities that would cause it to spoil. Any expiration date on a sealed bottle refers to the container's integrity over time, not the water inside. Once the container is opened, however, it is susceptible to contamination.

For long-term storage, the best options are food-grade high-density polyethylene (HDPE) containers or glass bottles. They are less likely to leach chemicals into the water and offer better protection from contaminants than thinner plastics.

Once opened, distilled water should be kept in a clean, airtight container in a cool, dark place or in the refrigerator. Use it within a few weeks for best quality and to minimize the risk of contamination.

No, commercially bottled distilled water from a store is not sterile. While the distillation process removes most microbes, it is not bottled in a sterile environment and can become re-contaminated once exposed to air. Sterile water requires additional, specific processing and handling for medical use.

Yes, but with caveats. Sealed bottles of commercially prepared distilled water are excellent for emergency supplies. For long-term storage, be sure to store them properly and rotate your stock periodically. Since it lacks minerals, it is not an ideal long-term, sole hydration source.

Signs of contamination include cloudiness, an unusual odor (chemical or moldy), algae growth, or a flat or off-taste. If you notice any of these signs, the water should not be used, especially for medical purposes.