How Long Can You Store Alkaline Water in Plastic Bottles?

November 22, 2025 •

4 min read

According to a 2023 study by Panasonic, ionized alkaline water stored in a plastic container can lose its beneficial properties and return to a neutral pH in as little as 48 hours. This means knowing how long you can store alkaline water in plastic bottles is crucial for preserving its advertised benefits.

Quick Summary

Storing alkaline water in plastic bottles is generally only viable for a very short duration, typically 48-72 hours, before its potent alkalinity and antioxidant properties degrade. Factors like temperature, light, and plastic type significantly impact how quickly the water's quality changes.

Key Points

Alkaline Properties Degrade Quickly: The elevated pH and negative ORP of alkaline water are temporary and can diminish significantly within 48-72 hours when stored in plastic bottles.
Heat and Sunlight Accelerate Leaching: Exposure to high temperatures or direct sunlight causes plastic to leach chemicals like antimony into the water, potentially affecting its purity and taste.
BPA-Free Doesn't Mean Perfect: While BPA-free plastic is an improvement, other chemicals can still leach into the water, particularly with prolonged storage or temperature fluctuations.
Glass and Stainless Steel are Superior: For long-term storage, glass or vacuum-sealed stainless steel containers are the best choice, as they are inert and protect the water from light and air.
Limit Air Exposure for Best Results: Filling storage containers to the brim minimizes oxygen exposure, which helps slow the degradation of alkaline water's antioxidant properties.
Avoid Reusing Single-Use Plastics: Reusing single-use plastic bottles increases the risk of both chemical leaching and bacterial growth, as they are not designed for repeated cleaning.

Understanding Alkaline Water's Instability

Unlike standard purified water, alkaline water, especially ionized water, is inherently unstable. Its primary value—the elevated pH and negative oxidation-reduction potential (ORP)—is temporary and highly susceptible to environmental factors. The moment it is produced or opened, alkaline water begins to interact with its surroundings, particularly oxygen and light. This interaction causes the ORP to drop and the pH to slowly return toward a neutral state. When stored improperly, this process accelerates, rapidly diminishing the water's supposed health benefits. Storing it in plastic bottles introduces additional variables that can impact both water quality and safety.

The Problem with Storing Water in Plastic

Plastic containers are not inert. Over time and when exposed to heat or sunlight, plastic can leach chemicals into the water it contains. For single-use polyethylene terephthalate (PET) bottles, common chemicals like antimony can be released, while reusable plastics might contain compounds like BPA (though many are now labeled 'BPA-free') or other plasticizers. Heat significantly accelerates this leaching process, which can negatively affect both the water's taste and its chemical composition. While alkaline water is not chemically aggressive enough to cause rapid degradation, the long-term interaction, especially under poor storage conditions, is a notable concern. Furthermore, microplastics, tiny particles of degraded plastic, have been found in most bottled water brands, adding another layer of contamination risk. The porous nature of plastic can also allow vapors from surrounding chemicals (like gasoline or cleaning products) to permeate the container and taint the water.

Short-Term vs. Long-Term Plastic Storage

For short-term storage, such as for a day at work or during exercise, a BPA-free plastic bottle stored in a cool place is generally acceptable. The risks of chemical leaching and degradation of the water's alkaline properties are minimal within a 24-hour window. However, relying on plastic for long-term storage is not advisable for several reasons. Beyond the 48-72 hour mark, the quality of the alkaline water will have likely decreased significantly, and the risk of plastic-related issues increases substantially. The best practice for home-based alkaline water systems is to consume the water as fresh as possible, or to use superior storage materials if it must be kept for later.

Best Practices for Maximizing Alkaline Water Longevity

To preserve the properties of alkaline water, a few key strategies are essential:

Choose the right container: Opt for airtight glass mason jars or vacuum-sealed stainless steel bottles. Glass is inert and prevents any leaching, while stainless steel offers durability and complete light blockage.
Limit air exposure: Fill the container to the very top, leaving minimal air space. Oxygen exposure is a primary factor in the degradation of the water's ORP.
Control temperature: Store the water in a cool, dark place, ideally in a refrigerator. Heat and light are catalysts for chemical changes and can degrade both the water and the plastic container.
Avoid certain materials: Never store alkaline water in metal containers that are not stainless steel, as some metals can react with the water and alter its properties. Avoid reusing thin, single-use plastic bottles, which are more prone to degradation and chemical release over time.
Store away from chemicals: Keep all water containers, regardless of material, away from cleaning supplies, gasoline, or other strong chemicals whose vapors could permeate the plastic.

Comparison of Storage Containers for Alkaline Water


Feature	Plastic Bottles (Single-Use PET)	Plastic Bottles (BPA-Free)	Glass Bottles	Stainless Steel (Vacuum-Sealed)
Recommended Storage Time	24 hours (best)	Up to 72 hours	Up to 1 week	Up to 1 week
Effect on pH & ORP	Rapid degradation	Moderate degradation	Slowest degradation	Slowest degradation
Chemical Leaching Risk	High, especially with heat	Low to Moderate (depends on plastic)	None	None
Protection from Light	Poor	Poor (often clear)	Poor (often clear)	Excellent (opaque)
Durability & Reusability	None	Good	Excellent	Excellent
Cost	Very low	Low to Moderate	Moderate	High
Best For	On-the-go, immediate consumption	Daily use, short transport	Refrigerator storage	Long-term home or office use

The Risks of Improper Plastic Storage

Beyond the loss of alkaline properties, improper storage of water in plastic bottles poses several risks. Exposure to heat and sunlight not only encourages chemical leaching but also promotes bacterial growth within the bottle, especially if it is reused and not properly cleaned. The scuffs and scratches that develop on reused plastic provide perfect breeding grounds for harmful bacteria. While bottled water is generally safe to drink long past its printed date, this applies to unopened, standard bottled water and assumes proper storage away from heat and light. For delicate alkaline water, these conditions are more critical, and its intended benefits will be lost long before any microbial contamination becomes an issue. For those who prioritize health and purity, understanding these risks is essential for making informed hydration choices. The best course of action is to reserve plastic containers for the shortest possible storage periods and to switch to glass or stainless steel for anything longer than a day.

Conclusion: Prioritize Short-Term Use in Plastic

Ultimately, the duration you can store alkaline water in plastic bottles is quite limited if you want to preserve its intended properties. While the water remains potable for longer periods under proper conditions, its elevated pH and antioxidant potential begin to degrade noticeably within 48 to 72 hours. The potential for chemical leaching, especially when exposed to heat or sunlight, further reduces the desirability of plastic for long-term storage. To get the full benefits of alkaline water, consume it as soon as possible after producing or opening it. For any storage need beyond a day, transitioning to glass or vacuum-sealed stainless steel is the recommended best practice for maintaining both the water's quality and your peace of mind. For more information on safely storing emergency water supplies, see the guidelines from Ready.gov on Storing Water.

Frequently Asked Questions

While the water itself does not 'expire' in the traditional sense, alkaline water stored in plastic bottles will lose its beneficial properties, like its elevated pH and antioxidant potential, typically within 48 to 72 hours. The water may remain safe to drink for longer under proper storage, but the alkaline benefits will be gone.

The best way to store alkaline water is in an airtight, non-reactive container such as a glass mason jar or a vacuum-sealed stainless steel bottle. Store it in a cool, dark place like a refrigerator and fill the container to the top to minimize air exposure.

No, it is not recommended to drink any water, including alkaline water, that has been left in a hot car. High temperatures accelerate the leaching of chemicals from plastic bottles into the water, which can affect both its quality and safety.

While BPA-free bottles are a better option than those containing BPA, they are not a perfect solution. Other chemicals can still leach from the plastic over time, especially with exposure to heat or wear. Glass and stainless steel remain the safest and most inert storage options.

The most accurate way to check the potency is to use a pH testing kit. A simpler indicator is taste; if the water no longer has a distinctively smooth or different taste, its alkaline properties have likely diminished significantly. Time is the biggest factor; if it has been stored in plastic for more than 72 hours, assume the benefits are gone.

It is not recommended to reuse single-use plastic bottles. They are not designed for repeated use and can easily become scratched, creating surfaces where bacteria can multiply. Furthermore, they are more susceptible to breaking down and leaching chemicals with reuse.

Freezing alkaline water in plastic bottles is not recommended. While freezing can preserve some water properties, the expansion of freezing water can damage plastic containers. For optimal quality, refrigeration is the better option.

Yes, plastics, particularly those used for beverage bottles, can be permeable to certain vapors. It is crucial to store plastic-bottled water away from strong chemicals like gasoline, paint thinners, and pesticides to prevent their odors and vapors from contaminating the water.