A friend of a friend was raving about her Hydro Flask, so I had to buy one of my own—and it was completely game-changing. I loved it so much that I used it both on and off my mat, day in and day, out for a handful of years… even when it was clearly past its prime. It took some convincing from a friend who was horrified at the bacterial buddies living at the bottom of the bottle (I know… don’t @ me), but I finally pulled an Ariana Grande and gave it a thank u, next for a new but no-less beloved Hydro Flask. About two or so years in, this one is starting to manifest signs of being worse for wear.

This got me thinking: When is it *officially* time to bid farewell to your reusable water bottle? Food safety expert Trevor Craig, corporate director of technical training and consulting at Microbac Laboratories, outlines the when and why ahead.

3 signs it’s time to replace your reusable water bottle

1. Your bottle has internal wear and tear

Personally, I don’t mind a few visible chips and dents on my insulated water bottles. But Craig says it’s more pertinent to investigate similar signs of wear and tear on the inside. “If you’re seeing a lot of cracks, discoloration, scratches, or cracks in your bottle, it is time to replace it,” he says. You might think these are innocuous, but there’s more at play than looks alone. “Scratches, cracks, and breakdown of the lids are spaces where bacteria can get in and start breaking down material even more.” You can think of them as small but potentially disruptive hideaways for pathogens to set up shop and contaminate your H2O. And it turns out they can really pile up.

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Per a 2022 study by independent company Water Filter Guru, the bottles tested had an average of 20,800,000 CFUs (colony forming units, or viable microbes). This measurement had 40,000 times (!) the bacteria on a toilet seat and 14 times the amount in a dog bowl. Yikes.

2. Your water is starting to taste or smell funky

Naturally, one of the easiest signs that your reusable bottle should be tossed is if something is off with the taste of your water. “If you start to taste or smell a metallic flavor or scent, it can be a sign it’s time to replace your water bottle,” Craig says. “Typically, it’s very closely related to the above. As bacteria grows and wears away the material, you might start to get a metallic flavor or scent.”

3. Discoloration and resistance to cleaning

The final sign indicating that it’s time to part ways is if discoloration (not to mention those strange smells) “will not go away no matter how long you soak or clean it,” says Craig. “Discoloration that doesn’t clean easily is likely caused by bacteria growth and breakdown of the bottle.” In addition, he recommends looking at the seal or the lid for discoloration and scratches as well, as they’re also susceptible to harboring bacteria.

How long do water bottles typically last?

According to Craig, the lifespan of your bottle will vary based on its composition and how well you clean it. If you keep them in good condition—by cleaning them with water, soap, and a brush that’ll reach all their nooks and crannies—they can have relatively long runs. “Just make sure the brush is designed for light cleaning and isn’t going to scratch or damage the bottle interior,” he advises. Moreover, he urges you to wash them every day after use… or, at the very least, every two to three days. If you’re resistant to the idea of this level of upkeep, you can always rotate between a few bottles. You may also want to invest in high-tech cleaning devices (think self-cleaning, UV gadgets), which Craig says are perfectly acceptable.

When kept scratch- and stink-free, most reusable bottles should last at least a year or longer. “[Hard plastic] bottles are typically good for about a year, while a metal reusable water bottle is most likely good for about three years,” Craig shares. “Glass is similar to metal water bottles, but they are easier to break or crack, which ends their shelf life right away.” He also cautions against exposing reusable plastic bottles to extreme heat or direct sunlight. (Note to self: Pack an alternative for hot yoga classes and trips to the beach.)

Lastly, if you absolutely need to opt for a single-use water bottle, be sure to keep it to single-use only. “[Their] plastic isn’t designed for reuse, which can break down and seep dangerous chemicals,” he warns. Spare the earth and your health by keeping your handy dandy multi-use, clean-as-a-whistle bottle in tow instead.