Does Distilled Water Go Bad?

Although you may find an expiration date on a bottle, in theory an unopened bottle of distilled can last for many years if stored correctly (more in this later).

However, if stored incorrectly – for example exposed to sunlight or excessive heat – then yes, distilled water can go bad and bacteria may start growing in the water.

Once opened, the water should be used within a few days if it’s intended to be drunk, but an opened bottle can last two years or more if you’re planning to use the water for household appliances rather than drink it.

What Is Distilled Water?

Distilled water is a type of water that has undergone a process to remove contaminants and minerals.

The process involves boiling water into a vapour and then condensing it back into a liquid in a separate container, which purifies the water and removes both positive and negative minerals.

Can A Baby Drink Distilled Water?

Yes, distilled water is safe to give to babies.

In fact, given it contains no minerals or impurities, and is free from contaminants and bacteria, some parents prefer to use distilled water when making up a bottle of baby formula.

Why Does Distilled Water Have An Expiration Date?

If stored correctly, then an unopened bottle of distilled water should last for many years, so you may be wondering why manufacturers add an expiration date to their product.

The reason is often because the container that the water is stored in can naturally degrade over time.

Plastic can begin leaching (transferring or leaking chemicals) into the water over a long period, thereby affecting your (or in this case your baby’s) health.

So to be on the safe side, many manufacturers opt to put a shelf-life of 3-5 years on distilled water.

Can Distilled Water Grow Bacteria?

Yes, bacteria can grow in distilled water.

If contaminants find their way into an unopened, sealed container of distilled water then this can result in the growth of bacteria.

Signs that bacteria has entered a bottle of distilled water include:

Green Algae: if there is algae growing in your water, this is likely because it has not been sealed tightly or has been left open for too long, as is of course a sign that it should be thrown away.
Unpleasant Odor: distilled water should have a bland taste and no smell, so if the water smells “off” or like chemicals then it’s not safe to drink.
Cloudy Appearance: distilled water should be very clear, so any forms of cloudiness means the water has been contaminated.

If you notice any of these signs then you should discard the water immediately as it won’t be safe to drink.

How To Store Distilled Water After Opening?

Storing distilled water is simple if you follow a few simple instructions:

Keep the container tightly sealed after opening to prevent air from getting into the container.
Store in a cool, dark place (or a refrigerator if you can).
Avoid direct sunlight, especially if the water is in a plastic container (sunlight can disintegrate plastic, causing chemicals to leak into the water).
Store in a glass bottle if possible for the reason above.
Avoid warm environments as these can speed up the time it takes for bacteria to grow.

Does Distilled Water Have To Be Refrigerated After Opening?

No, it is not essential to store an opened bottle of distilled water in the refrigerator.

However, if you have the space and are able to do so, it might be a good idea to store opened distilled water in the fridge.

This is because a refrigerator is a cool and dark environment, so the water won’t be exposed to sunlight or warmth (two things that can cause bacteria to grow).

How Long Does Distilled Water Last Once Opened?

This will depend on what you’re planning to use the water for.

If you’re going to use the distilled water in appliances like a humidifier, then an opened bottle may last up to two years or more if stored correctly (see above).

However, if you are giving the water to your child, perhaps by mixing it with baby formula straight from the fridge, then it’s best to use up the opened bottle of distilled water with 2-3 days.

Can You Freeze Distilled Water?

Yes, unlike freezing formula (which is a contentious subject), distilled water can be frozen, and should freeze at 0 degrees Celsius.