What Happens When Plastic Water Bottles Get Hot?

What Happens When Plastic Water Bottles Get Hot?

As the mercury rises, so too does our thirst.

Every day, we reach for that conveniently stored plastic water bottle in the car, at home, at work, etc, without giving it a second thought. But have you ever wondered what happens when that plastic water bottle gets hot?

What Happens When Plastic Water Bottles Get Hot?

You know, it’s funny. We often use plastic water bottles without giving much thought to what they’re made of or what could happen to them under different conditions. I mean, they’re just bottles, right? But, like many everyday items, there’s a bit more to them than meets the eye.

When a plastic water bottle gets hot, the first thing to know is that it doesn’t just sit there unaffected. Nope, there’s a whole lot going on.

Heat can cause the plastic to soften, and if it gets hot enough, the bottle might even start to lose its shape. Now, that might not be a big deal if you’re just worried about your water tasting a bit plasticky, but there’s a bit more to it.

You see, most plastic water bottles are made from a type of plastic called polyethylene terephthalate, or PET for short.

PET is generally considered safe for use, but when it gets hot, it can start to release substances like antimony and bisphenol A (BPA). These aren’t things you’d usually want in your water. In fact, some studies have suggested that they might have potential health effects.

That’s not to say that drinking from a warm plastic bottle is going to immediately harm you. The amounts of these substances released are usually quite small, and a single exposure is unlikely to cause serious harm.

But it’s definitely something to keep in mind, especially if you regularly leave your water bottles in hot places.

At this point, you might be wondering what you can do about it. Well, one simple step is to keep your water bottles out of the heat as much as possible.

And if you notice your water starting to taste a bit off after being in a hot bottle, it might be a good idea to get a fresh one.

Are there Plastics that are Better and Safer when Hot?

Different types of plastic have different heat tolerances. You see, not all plastics are made equal.

One type of plastic that’s often used for its better heat resistance is HDPE, which stands for high-density polyethylene. It’s a sturdier sort of plastic, and you’ll often find it used in things like milk jugs or cleaning product bottles.

HDPE doesn’t release harmful substances as easily when it gets hot, making it a safer choice if you’re expecting your bottles to be in a warm environment.

PP, or polypropylene is also a safe bet when it comes to heat resistance. These plastics are often used in containers meant for hot food, like disposable takeout boxes.

They’re also used in reusable food storage containers that you can put in the microwave. So, if it can handle hot food, you can be pretty confident it’ll stand up to a warm day.

But here’s the thing.

While these plastics are safer when hot, the best way to avoid any risk from heated plastic is to use alternatives when you can. Glass or stainless-steel water bottles, for example, don’t have the same issues with heat. They’re also more durable and reusable, which is a win for both you and the environment.

Ranking Of Plastics Based On their Compatibility When Hot

Type of PlasticSafety When Hot (Max Service Temperature in °F)Common Uses
PET (Polyethylene Terephthalate)Low (230°F)Beverage bottles, food jars, polyester clothing
HDPE (High-Density Polyethylene)High (170°F)Milk cartons, detergent bottles, toys
PVC (Polyvinyl Chloride)Low (140°F)Plumbing pipes, credit cards, medical tubing
LDPE (Low-Density Polyethylene)Moderate (N/A)Cling wrap, garbage bags, beverage cups
PP (Polypropylene)High (180°F)Straws, hot food containers, disposable diapers
PS (Polystyrene)Low (N/A)Cups, takeout containers, building insulation
OtherVariesEyeglasses, electronics, lighting fixtures


It’s clear that not all plastics are created equal when it comes to heat tolerance. While some, like HDPE and PP, are better suited for warmer environments, others can present potential hazards. The key takeaway? Be aware of the type of plastic you’re using, especially if it’s going to be exposed to heat.

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