Like any water type, distilled water can go bad. However, distilled water is far less likely to go bad than normal tap water because it has been treated with a purification process known as distillation.
The shelf life of unopened distilled water is indefinite. The manufacturer might advise a best-before date around 3-5 years into the future, but as long as the water is stored correctly.
The shelf life of opened distilled water is 12 months, as long as the water is stored properly in glass bottles with lids. Ideally, store the water in your refrigerator or in a cool, dry place.
– Exposure to dust or airborne particles – Contamination from the materials in the storage container – Airborne contamination that enters the water through a damaged container
If you usually drink distilled water, you’ll know that it has a pretty bland, “flat” taste. When drinking distilled water that’s gone bad, you may notice unusual or unpleasant water tastes.
You can keep distilled water for up to 12 months after opening, depending on your purpose.