Can You Put Solo Cups In The Dishwasher? | Heat Damage Risk

You just rinsed out a red Solo cup after a party, and instead of tossing it, you slide it into the dishwasher for a quick clean. It feels thrifty — why waste a perfectly good cup when the machine can wash it, right?

The problem is that classic red Solo cups are single-use items made from thin plastic. Most standard dishwashers run at temperatures high enough to soften or distort the cup, leaving you with a bent, useless result. This article explains which Solo cups can and cannot go in the machine.

Why The Dishwasher Can Damage A Solo Cup

Standard disposable Solo cups are made from #6 plastic (polystyrene). According to Solo’s official product information, this is a thin, single-use material not designed to withstand high heat. It’s the same plastic used in takeout containers and clear deli lids.

Most dishwasher cycles reach temperatures between 120°F and 160°F. Some plastic drinkware can begin to warp at temperatures as low as 100°F, meaning your standard cup faces heat stress from the very start of the cycle.

The exception: Reusable Solo cups

The manufacturer makes reusable cups that are specifically designed for repeated use. These are typically thicker and labeled as dishwasher safe. The standard red party cup, however, is not one of them.

Why People Wonder About Solo Cups Dishwasher

It’s easy to assume all plastic cups are the same. Disposable cups look sturdy enough, and if plastic takeout containers go in the dishwasher, why not a cup? The confusion comes from the fact that some plastic items are made to last and others aren’t.

Here’s how common plastic cup types compare for dishwasher safety:

• Standard red Solo cup (#6 polystyrene): Thin, single-use plastic that can warp or soften even in a gentle wash cycle. Not recommended for the dishwasher.
• Reusable Solo cup: Made from thicker plastic and explicitly labeled top-rack dishwasher safe by the manufacturer. These can be washed multiple times.
• Polypropylene (PP) cups: Can handle heat up to 180°F without losing shape, making them more dishwasher resistant than standard polystyrene cups.
• PLA cups (plant-based plastic): Safe only for drinks below 131–140°F. Dishwasher heat typically exceeds this range, causing them to soften and deform.

If you’re holding a classic red Solo cup, check the bottom for the recycling number. A #6 means polystyrene — keep it out of the dishwasher.

What Happens When Solo Cups Hit Dishwasher Heat

High dishwasher temperatures cause the thin polystyrene walls of a standard Solo cup to soften. The material loses its rigidity and can fold inward, tilt to one side, or develop visible wrinkles.

Once a cup warps, it’s no longer usable for holding liquid — the shape change can create leaks or an unstable base. This risk has been documented by sources like warp or melt, which notes that the high temperatures associated with dishwashers can damage standard disposable plastic cups.

The same softening effect can cause the cup to stick to the dishwasher rack or to other dishes, leaving melted plastic residue that is difficult to clean off.

If you place a standard Solo cup in the dishwasher, you risk ending up with a melted mess instead of a clean cup. Stick to hand washing or simply toss it after one use.

What To Do With Used Solo Cups Instead

If you want to reuse a standard Solo cup, the safest approach is to wash it by hand with warm soapy water and dry it immediately. Avoid scrubbing too hard, as the thin plastic can scratch and develop weak spots.

Follow these simple steps to get the most out of a disposable cup without damaging it:

1. Rinse immediately: Empty the cup and rinse it with cool water before any residue dries and sticks to the plastic.
2. Hand wash gently: Use a soft sponge and mild dish soap. Hot water is fine but avoid boiling water or prolonged soaking.
3. Dry with a towel: Pat the cup dry rather than letting it air dry, which can leave water spots on thin plastic.
4. Inspect for damage: If the cup shows cracks, warping, or a cloudy haze, it’s time to recycle it and grab a fresh one.

The same hand-washing approach works for any thin disposable plastic cup. You’ll extend its life for one or two more uses, but don’t expect it to last like a proper reusable cup.

Other Heat Concerns For Solo Cups

If the dishwasher isn’t safe, what about the microwave? Standard disposable Solo cups should also not go in the microwave. The heat can cause them to soften, warp, melt, or leak.

Per the not microwave safe guidance from Thedoublewave, the thin polystyrene material is not designed to handle direct heat exposure. Always check for a microwave-safe symbol on any plastic cup before heating it.

Even hot liquids — anything above about 140°F — can soften a standard Solo cup if left sitting long enough. For hot coffee or tea, a ceramic mug or an insulated tumbler is a much safer choice.

The Bottom Line

Standard disposable Solo cups are not dishwasher safe. The thin #6 polystyrene plastic softens and warps under typical dishwasher heat, leaving you with a deformed cup that’s no longer useful. Reusable Solo cups, polypropylene cups, and other heat-resistant plastics are fine on the top rack, but the classic red party cup belongs in the recycling bin after one use — or at most, a quick hand wash.

If you want to reuse disposable cups for multiple parties, check the bottom for a #5 PP symbol, or look for the manufacturer’s reusable line that explicitly states dishwasher safety. For the standard Solo cups you already have, hand washing is the only safe option.