Expert answer: How long can opened bottled water be kept?
1. How long can opened bottled water be kept?
“Once opened, bottled water can be kept for 4 to 6 days if kept in the refrigerator. If kept outdoors, in cool conditions and away from direct sunlight, the water can only be kept for a maximum of 3 days.”
According to the U.S. Food and Drug Administration (FDA) , unopened bottled water, if stored properly (in a cool, dry place, away from direct sunlight), can last for several years. Bottled water companies typically print the manufacturing and expiration dates on their bottles primarily out of concern for taste changes over time, not safety concerns.
However, according to Buxton Mineral Water , a Nestlé-owned mineral water bottling and extraction company, bottled water left outdoors should be consumed within 3 days of opening. Crystal Geyser Alpine Spring Water, a popular bottled hot spring brand in the United States, believes that once opened, the shelf life of bottled water will be limited. Although there is no definitive answer to this question, it is recommended to drink all the water in the bottle within 4 to 6 days after opening.
In addition, Mountain Valley Spring Water - an American bottled spring water brand also said that once the bottle of water has come into contact with the air, hands or mouth of the drinker, it should be consumed as soon as possible. If stored in the refrigerator, the water can retain its quality for 4 to 6 days after opening.
However, according to Mutosi, you should still not use opened bottled water past the recommended time above. Because in addition to factors such as plastic material and temperature, the environment from the air, hands, and mouth can cause the risk of cross-contamination in the water.
Compared to bottled water, bottled water has a much shorter shelf life. Specifically, unopened bottled water can be stored for about 6 months, and after opening it should be used up within 7-15 days. If stored longer, the water can easily become contaminated with bacteria and viruses, affecting health.

Bottled water also has an expiration date after opening.
2. How to properly preserve bottled water
Improper storage of bottled water can create conditions for bacteria and algae to grow, which can be harmful to health. Olympian Water Testing , a company specializing in providing clean and safe drinking water in the US, warns that consuming spoiled water can lead to serious health problems. The company also offers some tips to ensure the quality and safety of bottled water:
- Read the packaging carefully : Refer to the information on the expiry date, storage instructions and related warnings usually printed on the packaging. At the same time, make sure to follow these instructions to keep drinking water safe. all
- Pay attention to the storage environment : Bottled water should be stored in a cool place, away from direct sunlight and high heat sources. Humidity is also an important factor, so you should keep the water in a dry place and away from chemicals that can cause contamination.
- Limit direct contact : If you cannot drink all the water at once, you should not drink directly from the bottle mouth and limit touching the bottle mouth to avoid contamination from your hands or mouth into the water.
- Store water bottles upright : Storing water bottles upright helps prevent bacteria from entering the water and preserves water quality longer.
- Check before reuse : Every time you use opened bottled water, inspect the bottle to make sure there are no signs of damage such as deformation, leakage or unusual taste.

You should not drink water directly from the bottle.
3. Harmful effects of drinking bottled water that has been left for more than 3 days
Bottled water can lose its original freshness if left out for too long, especially after opening. If water is exposed to the outside environment overnight, its chemical composition can change, making it taste slightly sour compared to new water.
According to Clean Water Action , the largest environmental organization in the United States, most bottled water today is contained in plastic bottles made from Polyethylene Terephthalate (PET). Although PET does not contain BPA (an industrial chemical that can affect fertility), when exposed to high temperatures or stored for too long, it can release phthalates, a substance that can disrupt hormones if humans are exposed for a long time.
In addition, Hai Duong newspaper also warned that leaving water open for too long will create conditions for bacteria and viruses to grow, making the water smell bad, reducing quality and potentially causing many health risks.

Bottled water when exposed to the outside environment for too long can become contaminated with bacteria, affecting health.
It can be seen that using bottled water after opening the lid for too long can not only affect health but also reduce the experience of using water. Therefore, in families, companies or schools, water purifiers are still the ideal and safest solution.
In particular, with Mutosi water purifier, you can completely trust the quality of the output water. Water is always continuously filtered according to demand, removing up to 99.99% of impurities, dirt and bacteria thanks to the Slitec RO filter core. Moreover, the Nano Silver core helps prevent re-infection during storage, ensuring that the water is always pure and safe for the health of the family. Mutosi water purifier not only provides clean water but also also creates convenience, helping you feel completely secure in daily use. Besides, in the long run, using a water purifier also brings significant savings for you and your family.
To learn more about convenient and quality water purifiers, please visit the page: Mutosi Water Purifier - Protect and improve health according to Japanese standards.

Water purifier provides fresh water that is always safe for health.
To ensure your health, it is best to drink the entire bottle of water after opening or store it in the refrigerator and use it within the shortest time possible. If you need to use water for a long time, choosing alternative solutions such as water purifiers will bring more convenience and peace of mind to your family.