How long does it take for an open bottle of water to go bad?

Quick Answer

An open bottle of water can go bad in as little as a few days or up to 6 months if stored properly. The factors that determine how long an open bottle of water will last include the initial quality of the water, exposure to contaminants, temperature, air exposure, and light exposure. An uncontaminated bottle stored in a cool, dark place and consumed within a week is generally safe.

Does Bottled Water Go Bad?

Yes, bottled water can go bad, but it takes longer than other beverages. When water is bottled, it goes through filtration and disinfection processes to remove contaminants and kill bacteria. This gives bottled water a longer shelf life. However, bottled water still contains trace amounts of minerals and nutrients that can degrade over time.

Once opened, bottled water is exposed to air and light which speeds up chemical reactions. The minerals and nutrients can start to break down, causing subtle changes in taste, odor, and appearance. Over time, bacterial growth is also more likely in an opened bottle. So while bottled water is sterile when sealed, its quality deteriorates gradually once exposed to air.

Signs Your Bottled Water Has Gone Bad

Here are some signs that indicate your bottled water may have gone bad:

– Change in taste – Starts to taste flat, acidic, or salty

– Change in smell – Develops a chemical-like odor

– Change in color – May look cloudy or tinted

– Algae growth – Greenish tint and musty smell

– Bacterial growth – Slimy residue, slippery texture

– Sediment – Particles floating at bottom of bottle

– Bottle bloating – Bulging out due to gas production

If you notice any of these signs, it’s best to throw out the water and get a fresh bottle. Drinking spoiled water can cause unpleasant symptoms like nausea, cramps, and diarrhea.

Factors That Affect How Long Bottled Water Lasts When Open

Several factors impact how long an open bottle of water will stay fresh:

Initial Water Quality

Higher quality water that goes through more rigorous purification will last longer. Distilled or purified water has very low amounts of minerals and contaminants to begin with. On the other hand, spring water and mineral water contain more solids so they tend to degrade faster.

Exposure to Air

Once exposed to oxygen, chemical changes occur faster. Aerobic bacteria also gain access to multiply when the water bottle is opened.


Heat accelerates chemical reactions and bacteria growth. Storing an open bottle at room temperature will make it go bad quicker compared to refrigeration.

Light Exposure

UV rays from sunlight can interact with oxygen and water to hasten chemical breakdown. Storing opened water in the dark helps extend shelf life.

Initial Contamination

If contaminants are introduced during the bottling process or after opening, they will multiply, making the water go bad faster. Poor hygiene when drinking directly from the bottle can introduce bacteria.

How to Make an Open Bottle of Water Last Longer

Here are some tips to extend the shelf life of an open water bottle:

– Store in the refrigerator – Keep at 40°F or below
– Avoid extreme heat – Don’t leave in hot car or direct sunlight
– Drink from a cup – Don’t reintroduce mouth bacteria by drinking directly
– Keep cap on – Limit air exposure by sealing after use
– Use clean cups – Use sanitized glasses to minimize contamination
– Check for smells – Discard if any off odors develop
– Watch for growths – Discard if you see any algae or slime
– Finish quickly – Try not to take more than a week to finish

With proper storage and handling, an opened bottle can stay drinkable for up to 6 months. But for best quality, aim to finish it within a week. If in doubt, remember it’s cheap and easy to replace with a fresh sealed bottle.

How Long Does an Unopened Bottle of Water Last?

An unopened, commercially sealed bottle of water can technically stay fresh for an extended period, often 2 years from the bottling date. However, water quality can degrade over time even when sealed:

– Plastic leaching – Plastics leach chemicals into water over years
– Oxygen permeation – Plastic allows slight air exchange over time
– Light exposure – Heat and UV can accelerate chemical changes
– Temperature fluctuations – Expansion and contraction alters water composition

So while sealed water won’t “go bad” from bacterial growth, taste and nutritional value may slowly change. For optimal quality, it’s generally recommended to drink bottled water within the first year. Note the “use by” or “best by” date if one is printed.

Some key signs that unopened bottled water has degraded in quality:

– Faded label – Indicates age and sun exposure
– Plastic smell or taste – Chemical leaching into water
– Cloudiness – Particulates or algae growth

Again, these issues do not make sealed water unsafe to drink, but indicate it may have an off taste or some nutrient loss. If you have an emergency bottle stored for long periods, be sure to check for any off qualities before drinking.

How to Tell If Your Bottled Water Has Gone Bad

Here are some simple ways to tell if your bottled water has gone bad:

Check the Smell

Give the bottle a sniff when you first open it. Fresh water should not have any odor. If it smells chemical-like or rotten, it has gone bad.

Look for Sediment

Empty some water into a clear glass. Bad water may contain tiny particles that settle at the bottom. Good water should be clear.

Check the Color

The water should look crystal clear and colorless. If it’s tinted or cloudy, those are signs of contamination.

Taste It

Take a small sip. The taste should be neutral. Off-flavors like bitterness, staleness, or saltiness indicate spoilage.

Assess the Texture

The water should feel smooth and wet. A slippery, slimy mouthfeel means bacteria growth. Fizziness or foam is also a bad sign.

Look at the Expiration Date

Check if the bottle has passed the “use by” or “best by” date printed on the label. If so, discard it.

Consider How Long It’s Been Open

Toss opened water bottles after a maximum of 6 months. Even if it was stored properly, the quality degrades over time.

Check for Bottle Bloating

Bulges or stretched plastic indicate gasses from bacterial growth inside. Swelling is a clear warning sign to throw out the water.

When in Doubt, Throw it Out!

If you notice any changes or are uncertain, don’t take chances. Discard and open a fresh water bottle.

Health Risks of Drinking Spoiled Water

Drinking spoiled bottled water can negatively impact your health:

Gastrointestinal Distress

Consuming water containing harmful bacteria or toxins can cause nausea, vomiting, cramping, and diarrhea within 30 minutes to several hours.

Respiratory Infections

Some molds and bacteria in foul water can infect the sinuses, throat, and lungs if inhaled or aspirated during swallowing. This may lead to illness within 1-7 days.

Kidney Problems

Contaminants and toxins can damage kidney cells and lead to acute kidney inflammation in the days following ingestion.

Liver Function Decline

If the liver has to filter high levels of pathogens or toxins from bad water, its function can be compromised. This may manifest 2-3 days later.

Weakened Immune System

Constant exposure to heavy microbial loads in spoiled water can make you more prone to all types of infections, from colds to serious diseases.

Cancer Risk

Over many years, carcinogens leaching from plastic bottles are theorized to potentially increase cancer risk in those who regularly drink the water.

To avoid any of these health consequences, be vigilant about discarding water that shows any signs of spoilage. The risks outweigh the small cost savings of trying to finish water that’s gone bad.

Can You Boil Bad Bottled Water to Make it Safe Again?

No, boiling water that has already spoiled is not guaranteed to make it safe to drink again. Here’s why:

May Still Contain Toxins

Boiling can kill most bacteria, viruses, and parasites. But it does not remove chemical toxins like heavy metals that could leach from the plastic bottle into bad water over time. These toxins can persist even after boiling.

Can Concentrate Contaminants

Boiling water evaporates the pure water, leaving behind any dissolved solids or particulates. So while it kills bacteria, the contaminants become more concentrated rather than eliminated.

Affects Taste, Color, Smell

Boiling changes water’s taste, appearance, and odor as gases dissipate. Even if it’s safer, the quality degradation remains.

May Reintroduce Microbes

If you transfer boiled water back into a dirty bottle, it can easily become re-contaminated with new bacteria. Proper sanitization is critical.

Not Worth the Risk

Given all these limitations, boiling spoiled water is not guaranteed to make it potable again. It’s more prudent to discard water that smells, looks, or tastes bad after opening.

How to Store an Open Bottle of Water Properly

Follow these tips for storing open bottled water correctly to maximize freshness:

– Refrigerate immediately at 40°F or below. The colder the better.
– Screw the cap back on tightly to limit air exposure.
– Keep away from sunlight, heat sources like stoves, and windows.
– Store upright to minimize air contact with the opening.
– Wipe clean any drips from the lip or threads to avoid contamination.
– Use only sanitized drinking glasses to avoid introduce bacteria.
– If possible, transfer to an airtight glass container like a mason jar.
– Consume within 3-5 days for peak freshness.
– Throw away immediately if you notice any odd changes.

Proper refrigeration and limiting air exposure are most critical for keeping opened water fresh. Discard bottles once they start looking or tasting subpar – don’t take chances with your health.

Frequently Asked Questions

Can you drink bottled water after the expiration date?

It’s not recommended. While still generally safe, water taste and quality slowly decline after the printed expiration date. Stick to unopened bottled water within 1 year of bottling, and discard opened bottles after 6 months.

Does purified water go bad?

Yes, even purified water can go bad once opened. The most purified types like distilled and reverse osmosis last longest – up to 6 months in the fridge. But they still slowly degrade in quality so should be discarded in a timely manner.

Can old bottled water make you sick?

Yes, drinking expired or spoiled bottled water can make you sick. It may contain harmful bacteria, mold, chemical toxins, or plastic chemicals if stored for too long. Look out for changes in odor, clarity, or taste.

Can you drink water after opening if it tastes funny?

No, it’s safest to discard bottled water that tastes or smells funny. An off taste, like metallic or chemical notes, means it has started to degrade and could be unsafe if consumed.

How long does water last unrefrigerated?

Unrefrigerated, opened bottled water lasts 1-2 days. Without cooling, bacteria growth and chemical breakdown in the water speed up rapidly. For optimal freshness and safety, keep opened water chilled.

Is it safe to drink water left in a hot car?

No, heat speeds up bottled water’s degradation. Water left for hours in a hot car can become contaminated or absorb chemicals from the plastic more rapidly. Scorching temperatures make an opened bottle go bad almost instantly.

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