Unopened bottled water typically keeps until the best-before date on the label – usually one to two years. The limit comes from the plastic, not the water: water itself doesn't expire. That distinction is where this story actually starts.
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Does water expire? No – water is a stable substance; sealed and stored properly, it does not go off. What the best-before date on bottled water tracks is the packaging: over time, and faster in warmth and sunlight, plastic can pass traces and off-tastes into the water it holds. The date answers for the bottle, not for the water.
That is why storage decides more than time. Heat and UV light accelerate the migration of substances from plastic into water; a bottle left in a hot car ages faster than one in a cool cupboard. Opened bottles are a different story again – once air and contact enter, days matter, not years.
And here is the quiet irony worth noticing: the water inside was fine all along. In the UK, the water from your tap is held to monitoring at least as strict as bottled water's – it is safe as supplied. Which raises the question this article is honestly about: what are you buying when you buy the bottle?
If the answer is "better-tasting water", there is a way to get that from the tap – what filtering actually changes is covered in Benefits of filtered water.
Bottled vs tap: the fair comparison
Is bottled water better than tap water?
- On safety, in the UK: no – both are tightly regulated; tap water is tested more frequently.
- On taste: sometimes – mineral composition differs, and that is a legitimate preference.
- On cost and packaging, the ledger tilts hard toward the tap: what is drinkable water from your own kitchen costs a fraction of the bottled equivalent and carries no single-use plastic.
A fair comparison names all three columns – and lets you weigh them.
What bottled water actually is
Bottled water filtration and treatment vary by type:
- natural mineral water is bottled at a protected source with its mineral profile intact;
- spring water is similar with lighter rules;
- table water can be treated tap water.
Is bottled water good for you? It is safe and regulated – the honest answer is that in the UK, "good for you" is a property both kinds of water share.
Reducing plastic – without the sermon
How to reduce plastic use, practically and in order of impact: refill instead of rebuy (one reusable bottle replaces hundreds of single-use ones a year), choose larger formats when you do buy, and recycle what you can't avoid. No guilt attached — most plastic in circulation was never the consumer's design choice. Progress here is practical, not moral.
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Sources & further reading:
Health Canada
BBC
Medical News Today
Boston University Sustainability
Legislation.gov.uk
National Center for Biotechnology Information (1)
National Center for Biotechnology Information (2)
Last reviewed: July 2026
