Only wash plastic containers marked dishwasher-safe to avoid warping or chemical leaching.
- Place plastics on the top rack and skip the heated dry cycle to reduce heat damage.
- Hand-wash any plastic without a dishwasher-safe symbol, especially single-use or code 3/7 plastics.
What Makes a Plastic Container Dishwasher Safe?
Plastic containers marked with a dishwasher-safe symbol are designed to withstand the heat and moisture of a dishwasher cycle. This symbol typically shows a cup and plate with water droplets above them. The plastic type also matters; polypropylene (PP, recycling code 5) is generally safe, while polystyrene (PS, code 6) is not. Containers without a symbol should be hand-washed to avoid damage. According to the International Association for Food Protection, using dishwasher-safe plastics reduces the risk of chemical migration.
How Heat and Detergent Affect Plastic Containers
Dishwasher cycles use water temperatures between 120°F and 160°F, which can soften some plastics. This heat can cause warping, melting, or loss of shape, especially for thin or low-quality plastics. Dishwasher detergents are more alkaline than hand soap, which can degrade plastic surfaces over time. This may lead to clouding, cracking, or a rough texture. Owners report that repeated washing can make plastic containers absorb odors or stains. To minimize damage, place plastics on the top rack, away from the heating element.
Which Plastic Containers Should You Avoid in the Dishwasher?
Avoid putting single-use plastic containers, like takeout boxes or yogurt cups, in the dishwasher. These are not designed for repeated heat exposure and may warp or leach chemicals. Also avoid plastics with recycling codes 3 (PVC) and 7 (polycarbonate), as they may contain harmful additives. Containers with glued-on labels or decorations can peel or release ink. If a container has a melting point below dishwasher temperatures, it will deform. Check the bottom for a dishwasher-safe symbol or the words 'top rack only'.
How to Safely Wash Plastic Containers in the Dishwasher
Place plastic containers on the top rack, away from the heating element at the bottom. Ensure they are not nested or stacked, as water and detergent need to reach all surfaces. Use a gentle or eco cycle with lower heat if your dishwasher has one. Avoid using the heated dry cycle; instead, open the door after the wash to let them air dry. Hand-wash any containers with food residue that is hard to remove, as pre-rinsing is not recommended. Check containers regularly for signs of damage, and replace them if they become warped or cracked.
Dishwasher-Safe Plastic vs. Glass: Which Is Better?
Glass containers are always dishwasher-safe and do not absorb odors or stains. They are heavier and can break if dropped, but they last longer. Plastic containers are lighter and less likely to break, but they may need replacement over time. For long-term use, glass is often a better investment. However, plastic is more convenient for kids' lunches or outdoor use. Many people use both: glass for leftovers and plastic for on-the-go. The choice depends on your priorities, such as durability, weight, or cost.