Why Water Has an Expiration Date and How to Make it Last

Why does water have an expiration date.

Have you ever wondered why water has an expiration date? When you buy bottles of water from the store there is often a date of expiration printed on them. This may seem surprising since water itself never expires. This is of particular concern to those who attempt to stock pile large amounts of bottled water for extended periods of time, such as those storing water for emergencies.

The answer is that the water itself never really expires, but its container often does.

Knowing how to store water so that it lasts the longest possible time will give you peace of mind even in large regional disaster. You should be aware of how long water will actually last last, so you can take the appropriate actions to ensure that your water is always fresh. Bottles and other containers of water can often last longer than the expiration date that is printed on them. This is especially true in the right storage conditions.

How Long Does Bottled Water Last?

Water often has a date of expiration printed on its container or packaging. While water won’t “go bad” on its own, your water supply can still become contaminated over time, depending on how it’s packaged.

There are a few important reasons for why water has an expiration date printed on its packaging.

  • If the water is stored in a plastic bottle, leftover chemicals from the manufacturing process will leach into the water over time. Chemical degradation of the plastic container itself is also possible. This is especially true if the water is stored in hot climates. These chemicals from the plastic bottles can be toxic or harmful to human health. They can also give water a funny “plastic” like taste.
  • The plastic itself contains the chemical high-density polyethylene (HDPE). When this chemical is formed into a plastic bottle, the bottle will actually consist of microscopic pores in the plastic where water sits within them and are more exposed to tastes and smells from the surrounding environment.
The leeching of plastics into water is why packaged water has an expiration date.
Plastic water bottles will leech chemicals and degrade over time. Find other means to store water for extended periods.

So It’s the Container’s Fault? 

Solid plastic contaminates have been discovered in bottled water. Scientist Sherri Mason with the State University of New York, Fredonia, discovered that bits of plastic referred to as “microplastic” were present inside 93% of the samples taken from world’s bottled water brands such as Evian, Dasani, San Pellegrino and Nestle Pure Life. The samples she used in her testing originated from countries around the world, including the United States.

The concentration of this contaminant was 10.4 plastic particles per liter on average at a size of 0.10 millimeters. Plastic particles smaller in size were also found at a concentration of 325 particles per liter. Sherri Mason also states that bottled water is less safe than our tap water.

Bottled water is less safe than our tap water.

– Sherri Mason

State University of New York, Fredonia

The microplastic particles were shown to contain polyethylene terephthalate (PET), polypropylene and nylon. These are all chemicals used to manufacture the bottles, as well as, the bottle caps. Sherri Mason confirms that these plastic contaminants are due to the manufacturing process. These are all chemicals that may increase the risk of autism, ADHA and certain types of cancer.

Water filtered at the bottling plant may not be as clean as you think. The water produced during the manufacturing process may also get contaminated with microorganisms such as algae and bacteria. If the water filters have not been maintained and regularly cleaned, microorganisms can remain in the water.

Some of these microorganisms such as cyanobacteria and blue-green algae produce cyanotoxins that have been shown to disrupt the proper functioning of the liver, cause damage to the kidneys and cause tumors. Some of the toxins are neurotoxins which attack the nervous system and cause numbness, tingling, drowsiness, paralysis and even death.

In short, water bottled in plastic is less safe than tap water over prolonged periods of time, so store tap water in a non-plastic container. This is why plastic bottles have an expiration date.

Water Stored in Mylar Bags

Mylar is a polyester film that is made up of polyethylene terephthalate (PET) that is stretched in order to give it tensile strength. PET is not without its risks. Phthalates are known to be endocrine disruptors or compounds that disrupt the production of hormones within the human body.

Antimony, an element that is part of the PET molecule is also toxic and can cause health issues such as stomach ulcers, diarrhea, and vomiting. Antimony has the potential to seep into the liquid it is being used to package. The levels of this contaminant usually stay below the recommended level set by U.S. Environmental Protection Agency (EPA) when kept at or below room temperature.

Canned Water

Drinking water can also be canned and stored in aluminum cans as a way to prolong its shelf life. This is a very popular solution in the emergency preparedness realm since a long shelf life is critical. Purified water that is filtered and sterilized by UV light is hermetically sealed within the cans. For example, Blue Can Emergency Drinking Water uses a 12 step process to remove solid contaminants, chemical impurities and microorganisms from water. The water is then canned under pressure with nitrogen gas.

The can itself is coated with epoxy on the inside to protect the aluminum metal from degradation, rusting and contact with the water itself. The company that manufactures this water claims that their water has a shelf life of 50 years due to the treatment of the can with epoxy.

Glass Containers

Glass containers are extremely good at keeping the water inside safe from contamination. It is not porous like plastic is and will not allow outside smells to seep into the water. They will also not leech any chemicals into the water either. Make certain that the cap used in your glass container is of high quality as this is the weak point for keeping out contaminants.

The biggest down side to storing water for long periods of time in glass is that glass breaks. If it gets dropped or even knocked over from relatively low heights, it can shatter.

The Different Types of Water

  1. Distilled Water. This water goes through the distillation process where water is heated to its boiling point and evaporates as steam. This steam is then captured, cooled, condensed, and collected in a serrate container. This process removes all natural minerals. While this is beneficial for your appliances because there won’t be any mineral build-up, it’s not ideal for your body.
  2. Filtered Water. Filtering water removes impurities, bacteria, chemicals, and other contaminants by (typically) using carbon. The carbon molecule attracts some minerals and toxic chemicals. This does remove some of the ‘good’ minerals in the process however.  
  3. Purified Water. Purified water goes through similar steps as filtered water, but with additional steps such as distillation, reverse osmosis, carbon filtration, or deionization. It may also have small doses of iodine or chlorine added to clean the water.
  4. Spring Water. Spring water goes by many names, such as well water, groundwater, or even the fancy “artesian” water. This water may or may not be filtered. Because of this, it is higher in natural minerals which are good for you, and creates a better taste. However, it may not be as safe as the other listed options.
  5. Tap Water. Tap water is essentially the same as filtered water with the addition of a chemical treatment to ensure bacteria doesn’t grow in the water supply. This is usually done by adding small amounts of chlorine to the water. Actually, this addition of chlorine can drastically help tap water last when stored away for extended periods of time.

Each method is safe enough to pass EPA regulations and inspections, so really, the choice is personal to you and your family. 

Water being dispensed from water barrels.
Water type isn’t nearly as important as the type of container its kept in. Make sure you’re focusing on what matters.

Store in a Cool, Dark Location – Especially When Storing Water in Plastic or Mylar

Water should be kept in a cool location such as a basement or storage room so it is not exposed to warm or hot temperatures. As the temperature rises above room temperature, chemicals within the plastic containers or mylar will seep into the water at a faster rate. This can put your health at risk. Also be aware of exposing your water to ultraviolet light (UV). UV light can also cause the chemicals in plastic containers and mylar bags to seep into the water at a faster rate.

The longer you store water in plastic containers or mylar bags, the more exposure to the chemicals will increase. At higher temperatures, unhealthy amounts of these chemicals will pose an immediate threat to human health. This is why it is imperative to dispose of any water that has not been used by its expiration date. A good rule of thumb is to rotate the water out before its expiration date and replace it with water with a longer shelf life.

Personally, I prefer to change the water out every three months. This is a bit excessive, but it ensures my water still tastes good and incurs very little chemical seepage.

How to Beat the Expiration Date

Rotate your Water

Frequently rotate your water supply. By frequently rotating your water supply, you can ensure that there is always fresh water on hand. You can also prevent the water from developing any noticeable bad tastes from extended exposure of the water molecules to the outside smells while sitting in the pores of the plastic bottle. The frequent rotation will also help to ensure that none of your plastic bottles suffer degradation of the plastic from age or exposure to heat.

Use Potable Water Containers

Buy plastic water containers that are made specifically to store potable (drinking) water for extended periods. These plastic containers are still made of high-density polyethylene (HDPE) however if they are made from the factory with the long-term storage of potable water in mind, they are much more likely to be made of thicker plastics. This makes it more difficult for outside smells to get into the water through the pores of the plastic. Also, these factories pre-wash their containers thoroughly ensuring that all leftover chemicals from the manufacturing process are gone prior to shipment.

Use Stainless Steel or Aluminum Cans

As mentioned earlier, emergency water produced in aluminum canned form has a very long shelf life. Stainless steel containers are also a great option. Both aluminum and stainless steel resist corrosion and protects the water from outside smells or contaminants. This is even true when exposed to heat higher than room temperature, such as in a car on a hot day.

Glass and stainless steel water bottles mean there's no expiration on the water they contain.
Glass and stainless steel water bottles are a popular choice for storing water. They do not leech contaminants into the water inside. Theoretically, water stored inside this type of container will never expire as long as it stays sealed.


While bottled water, professionally manufactured emergency water, and other types of water that you purchase may have expiration dates printed on their containers, it doesn’t mean the water itself goes bad. It usually means the container used to hold the water will reach the end of it’s life. Fortunately there are other options available for storing water for extended periods of time, such as for emergencies.

Storing enough water for your family to survive a prolonged period of time while maintaining the water’s quality is incredibly important. If you can keep your water in a cool, dark location and remember to frequently rotate it, you should be fine. If not, it may be best for you to invest in canned water that will stay safe and tasty for decades to come. By knowing how to store water for the long term, such as for an emergency, you’ll be doing yourself and your family a huge service. 

What are your tips to make your emergency water last longer? Do you have any preferred methods? Tell us in the comments section down below. If you liked this post, be sure to share it with your friends and family you care about.

John Walter

John Walter is an emergency preparedness consultant with eight years of experience and training in related fields. He is a passionate prepper living in the Sacramento area of California.

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