5 Things You Should Never Put in Your Dishwasher
Your dishwasher is built tough — but certain items will quietly destroy the pump, clog the spray arms, or dull the interior coating over time. Our technicians see the damage regularly. Here is what to keep out.
- Cast iron and non-stick cookware both suffer real damage from repeated dishwasher cycles.
- Wooden utensils and cutting boards will warp and crack under sustained heat and moisture.
- Large food scraps are the number one cause of clogged spray arms and drain pumps.
- Certain 'dishwasher safe' plastics still degrade faster than labels suggest under high heat.
1. Cast Iron Cookware
Cast iron pans rely on a seasoned oil layer for their non-stick surface and rust resistance. Dishwasher detergent is specifically formulated to strip grease and oil — which means it strips the seasoning right along with it, leaving the pan exposed to rust. We also see cast iron cause chipping on the interior racks and tub coating due to its weight and rough surface.
2. Wooden Utensils and Cutting Boards
Wood absorbs water. Repeated exposure to a dishwasher's heat and moisture cycle causes wood to swell, crack, and eventually split or warp permanently. Beyond ruining the item, splintered wood fragments can also work their way into the pump assembly.
3. Large Food Scraps and Bones
Most people scrape plates before loading, but it is worth being thorough. Large scraps, bones, and fibrous vegetable skins are the leading cause of clogged spray arm nozzles and jammed drain pump impellers — one of the most common calls we run in Mableton. A dishwasher that leaves a gritty film or does not drain fully is very often dealing with exactly this kind of blockage.
4. Insulated Travel Mugs and Tumblers
Double-walled insulated cups are built with a vacuum layer between two walls of metal or plastic. The heat of a dishwasher cycle can compromise the seal on that vacuum layer, causing the insulation to fail permanently — you will not see the damage, but the mug will stop keeping drinks hot or cold.
5. Certain "Dishwasher Safe" Plastics
Not all plastics handle sustained high heat equally, even when labeled dishwasher safe. Thin plastic containers, especially older ones, can warp near the heating element at the bottom of the tub. Beyond the damage to the item itself, warped plastic that shifts during a cycle can block spray arms from rotating properly.
What This Means for Your Dishwasher's Lifespan
None of these items will destroy a dishwasher in a single wash. The damage we see in Mableton homes builds gradually — a pump straining against food debris for months, a spray arm partially blocked by a stray fragment, mineral and grease buildup from residue that never fully rinsed away. Being selective about what goes in the machine is one of the easiest ways to avoid an unnecessary dishwasher repair call down the road.
A Simple Habit That Helps Everything Above
Run a hot cycle with a cup of white vinegar placed upright on the top rack once a month. It cuts through grease film and mineral buildup that accumulates even with careful loading habits, and keeps the interior smelling clean.
Dishwasher Not Draining or Cleaning Properly?
Same-day appointments available throughout Mableton, GA and Cobb County.
Frequently Asked Questions
It is best to avoid it. Dishwasher detergent strips the seasoning that protects cast iron from rust, and the pan's weight can chip interior racks.
This is often caused by a clogged spray arm or drain pump, frequently from large food scraps that were not scraped off before loading.
Run a hot cycle with a cup of white vinegar once a month to prevent mineral and grease buildup inside the machine.
