Although the dishwasher is a modern kitchen marvel, there are still some things you really shouldn't wash in it if you want to extend the longevity of this item. Much like you shouldn’t be putting cast iron in the dishwasher unless you want it to be rusted, similarly, you should avoid putting plastic or metal tumblers in the machine.

The dishwasher can definitely compromise the function of the tumbler. The insulated tumblers are engineered to keep cold liquids cold and hot liquids hot, but the airspace between the layers of these cups that creates that insulation can be problematic in the dishwasher. Place it on the bottom rack, and you may find the seal breaking, allowing water to fill in that space.

If your tumblers slosh back and forth when unloading the tumbler, this means it has lost its effectiveness. However, if you do not want to wash your tumblers by hand, use the top rack, and don't go for the high heat when it comes time to dry your dishes. Additionally, if you find some unsightly stains on your tumbler, use a baking soda and water paste to remove them.