Top rack is usually fine. The bottom rack sits next to the heating element, which is where plastic warps, lids stop sealing and cheap containers collapse.
Dishwashers dry with heat from an element in the floor of the machine. Anything light on the bottom rack is close to it, and most food storage plastic softens well below the temperature that element reaches. This is why the same container can survive a hundred top rack cycles and die on its first bottom rack one.
| Top rack | Generally safe for containers marked dishwasher safe |
|---|---|
| Bottom rack | Warping, melting, lids that never seal again |
| Check for | A dishwasher-safe symbol, usually a plate under water droplets |
| Stains anyway | Tomato and curry stain plastic regardless of the cycle |
| Lightweight tubs | Flip over and fill with water, so they come out dirty |
How to load plastic
- Top rack only, every time, regardless of what the container claims.
- Angle containers face down so water drains rather than pooling.
- Weigh down light lids with something heavier, or they flip and fill with dirty water.
- Skip the heated dry cycle for a full load of plastic.
- Let plastic air dry fully before stacking, since trapped moisture is what makes it smell.
What happens when you get it wrong
- Warped rims that no longer seal. The container still works, the lid does not, which defeats the point.
- Melted plastic on the element. A genuine mess, and the smell takes several cycles to clear.
- Cloudy, chalky plastic. Detergent etching the surface, which is permanent.
- Orange staining. Tomato and turmeric stain porous plastic in any wash. Sunlight fades it surprisingly well.
Glass containers go anywhere in the machine, do not stain and do not hold smells. Heavier, and that is the only trade.
For lids that have lost their seal, replacements are usually sold separately for the main brands.
Frequently asked questions
Can you put plastic containers in the dishwasher?
On the top rack, yes, if they are marked dishwasher safe. The bottom rack is where plastic warps, because it sits closest to the heating element.
Why did my container warp on the bottom rack?
Dishwashers heat dry using an element in the base of the machine. Food storage plastic softens well below the temperature that element reaches.
How do you get tomato stains out of plastic?
Leave it in direct sunlight for a day or two. Sunlight bleaches the staining noticeably, and it works better than scrubbing.
Why do plastic containers come out wet when everything else is dry?
Plastic does not hold heat, so there is no residual warmth to evaporate the water. Angle them downward and expect to towel dry them.
Is it safe to reuse takeaway containers in the dishwasher?
Most are single use and not rated for it. They warp easily and are not designed for repeated heat.