In college, I had a friend who drank daily from a refillable water bottle and almost never washed it. Others in our friend group would call it “swamp water.” However, she never noticed (or admitted to) any health concerns.

Knowing what I do now about waterborne diseases, I wonder — how often should we really clean our reusable water bottles? What illnesses and infections did my friend miraculously avoid? And is there a difference in safety between glass, metal, and plastic bottles? 

Why Cleaning is Necessary

Bacteria need specific conditions to grow and multiply. Unfortunately, a refillable water bottle can provide the ideal environment for bacterial growth.

• Bacteria thrive in moist environments. Water bottles, by their very nature, are constantly exposed to moisture, making them susceptible to bacterial contamination.
• While many bacteria prefer moderate temperatures, many can still grow at room temperature. 
• Bacteria feed on organic matter. Even though water might seem free of nutrients, small amounts of saliva, food particles, or other contaminants can enter your bottle, providing enough nutrients for bacteria to multiply.
• If your water bottle isn’t clear or is often kept in a dark environment like a bag or a car, bacteria are more likely to grow. Darkness helps bacteria thrive since it limits exposure to UV light, which inhibits bacteria.
• Touching the mouthpiece or cap of your bottle with unwashed hands can introduce bacteria. Additionally, each time you drink, bacteria from your mouth can transfer to the bottle.

Several types of bacteria can grow in water bottles if they are not cleaned properly:

• E. coli: Often introduced from handling the bottle with unwashed hands. E. coli can cause severe stomach cramps, diarrhea (often bloody), and vomiting.
• Staphylococcus aureus: Can come from skin contact and can cause infections if ingested in large quantities. Symptoms may include nausea, vomiting, diarrhea, and severe stomach cramps.
• Pseudomonas aeruginosa: This bacteria thrives in moist environments and can cause a variety of infections, including skin rashes, ear infections, and respiratory issues.
• Campylobacter: Often found in contaminated water, it can cause campylobacteriosis, leading to symptoms such as diarrhea (often bloody), fever, stomach cramps, and vomiting.
• Salmonella: Commonly associated with food poisoning, it can also thrive in contaminated water. Symptoms include diarrhea, fever, stomach cramps, and vomiting.
• Vibrio cholerae: The bacteria responsible for cholera, an infection that can cause severe watery diarrhea, leading to dehydration and potentially death if untreated.

How to Clean Your Reusable Water Bottle

Preventing Bacterial Growth

To prevent bacteria from colonizing your water bottle, follow these best practices:

1. Daily Cleaning: Wash your bottle with hot, soapy water every day. Use a bottle brush to clean all parts, including the cap and any straws or spouts.
2. Thorough Drying: After washing, allow your bottle to dry completely. Leaving it upside down on a drying rack can help ensure that all moisture evaporates.
3. Regular Disinfection: Periodically disinfect your bottle by soaking it in a solution of one part white vinegar to three parts water for about 10 minutes, then rinse thoroughly.
4. Avoid Leaving Water Sitting: Do not leave water in your bottle for extended periods, especially in warm environments. Empty and rinse your bottle at the end of each day.
5. Use an Intact Bottle: If your bottle has cracks or signs of wear, replace it. Damaged areas can harbor bacteria and are difficult to clean effectively.
6. Proper Storage: Store your bottle in a cool, dry place with the cap off when not in use to allow for ventilation and prevent moisture buildup.

One study showed that even running your bottle through your dishwasher may not always flush out the bacteria we want to avoid:

Users may think that it is sufficient to simply put the bottle into the dishwasher for cleaning, but not all reusable water bottles are dishwasher safe, and/or the diameter of the bottle mouth may not permit water and detergent to enter with sufficient force to coat the interior surface.

— International Association for Food Protection

Different Materials = Different Levels of Safety?

Glass Bottles

Pros:

• Glass is free from chemicals like BPA and phthalates that are found in some plastics.
• Glass does not impart any taste to the water, ensuring a clean, pure drinking experience.
• Glass is recyclable and does not degrade over time, making it an environmentally friendly option.
• In one study, glass was shown to grow the least amount of bacteria versus the other common bottle materials.

Cons:

• Glass bottles can break if dropped, posing a risk of injury.
• They tend to be heavier than metal or plastic bottles, which might make them inconvenient to carry around.
• Glass doesn’t have the same temperature-stabilizing properties as insulated metal bottles.

Metal Bottles

Pros:

• Metal bottles, especially those made of stainless steel, are very durable and can withstand drops and impacts.
• Many metal bottles come with insulation, keeping your water cold or hot for longer periods.
• High-quality stainless steel bottles do not contain harmful chemicals.

Cons:

• Some people notice a metallic taste in their water, especially if the bottle is not of high quality.
• While generally lighter than glass, metal bottles can still be heavier than plastic ones.

Plastic Bottles

Pros:

• Plastic bottles are the lightest option, making them easy to carry.
• High-quality plastic bottles are durable and resistant to impact.
• Plastic bottles are usually less expensive than glass or metal ones.

Cons:

• Chemical concerns: Some plastic bottles contain BPA or other chemicals that can leach into the water. However, many manufacturers now produce BPA-free bottles.
• Odor and taste: Plastic can sometimes retain odors and flavors from previous contents, affecting the taste of your water.
• Environmental impact: Plastic, even when refillable, is less environmentally friendly than glass or metal.
• In one study, plastic was shown to harbor more bacteria than glass or metal bottles due to its more porous surface.

Regardless of the material, the most crucial factor is how you maintain your bottle. Regular cleaning and proper care are essential to ensure that your refillable bottle remains a safe and healthy way to stay hydrated.

Another consideration to keep in mind is the bottle’s design. Bottles with hard-to-reach crevices are more likely to grow mold without regular disinfection.

The Water We Drink

Those of us in Western countries have the option to conveniently refill our bottles with clean, safe water that we know won’t hurt us as long as our bottles are clean. But many people in sub-Saharan Africa don’t have that luxury. Only 31% of the population in sub-Saharan Africa has access to safely managed water.

Reading this article all the way through means you’d like to keep yourself and your family safe from water-related diseases. People in sub-Saharan Africa have that same desire, just with fewer resources to do so consistently and reliably.

We at The Water Project are working to ensure that everyone in our service areas of Kenya, Sierra Leone, and Uganda has access to safe, dependable water sources. Your generous gift can bring safe water sources like wells and protected springs to communities in Africa currently suffering from water-related illnesses.