Storage containers survive dishwashers reasonably well and behave differently from crockery in two specific ways.
They Come Out Wet
Not a fault. Dishwashers dry largely by heating items so that residual water evaporates from the hot surface.
Glass and ceramic hold heat well and dry themselves. Plastic has low thermal mass and cools almost immediately, so the water sits there.
Opening the door at the end of the cycle and letting steam escape, then leaving items to air dry, resolves it.
Top Rack Only
- The heating element sits at the bottom of most machines
- Plastic near it can distort, even if the water temperature is fine
- A warped rim no longer seals, which ruins the container
- Lids are lighter and get flipped by the spray on the lower rack
- Which is why care instructions specify top rack
Manufacturers stating top-rack dishwasher safe rather than dishwasher safe generally, of the kind at mysnapware.com, are describing a real distinction rather than covering themselves.
Secure the Lids
Light plastic lids flip over in the spray, fill with water and come out dirty on the underside.
Wedging them between rack tines, or using a rack designed for them, solves it. Lids that have flipped need rewashing rather than putting away.
Take the Gasket Out Occasionally
A dishwasher does not reach the channel beneath a gasket, and that is where residue and smell accumulate.
Peeling the gasket out every few months and washing both parts by hand is what keeps a lid fresh. Refit it evenly and the right way round.
Staining Is Not Dirt
Tomato, curry and turmeric stain plastic, and no dishwasher cycle removes it.
A bicarbonate paste lifts a good deal, and sunlight fades the rest. It is cosmetic provided the container has been washed properly.
Detergent Is Harsh
Dishwasher detergents are strongly alkaline, which over many cycles dulls and clouds some plastics.
Hand washing extends the life of anything you care about, which is a fair trade for items used daily.
Do Not Wash Glass and Plastic Loose Together
A light plastic item that shifts can knock a glass one, and chipped glass should be retired.
Dry Fully Before Storing
A container put away damp, particularly with the lid on, grows mould in the seal.
Store Lids Off
It lets both dry and lets the gasket recover.