You'll know it's time to delime your dishwasher if you notice a whitish buildup inside the appliance that doesn't easily wipe away. Sometimes you'll also see a filmy residue on your dishes. Periodically removing the limescale from inside the dishwasher will improve its performance and prolong the life of your dishes, since limescale can accelerate corrosion and rust.
If you have limescale in your dishwasher, you probably also have it around the faucets, on the showerhead, in your washing machine and even in your tea kettle. That's because limescale has nothing to do with the dishwashing process and everything to do with your local water supply. Once you know how to efficiently descale a dishwasher, you can use the same cleaner to spruce up all the water fixtures around your home.
Limescale in the Dishwasher
Limescale in your dishwasher is a direct result of living in an area with mineral-rich water, also known as hard water. "Hard" water regularly comes into contact with minerals — particularly calcium and magnesium — in the ground. The minerals dissolve in the water and travel wherever the water travels, even after the sanitizing process at your local water treatment facility. Whenever this water evaporates, the minerals are left behind as a tell-tale whitish film
You can install a whole-house water softener to remove these minerals from the water before it's piped throughout your home, preventing limescale from building up inside your dishwasher. In the meantime, learn how to regularly descale your dishwasher to prevent these mineral deposits from affecting your dishes.
Delime a Dishwasher
Vinegar is your best asset for cleaning a dishwasher plagued with limescale. Start by emptying the dishwasher of all dishes and utensils. This will allow the vinegar to come in full contact with the sides of the dishwasher without dishes hindering its path.
Don't pour the vinegar directly into the bottom tub of the dishwasher (it will just drain away) or into any of the detergent dispensers (they won't hold enough vinegar). Instead, fill a shallow dishwasher-safe lid, bowl or plate with vinegar and place it flat in the top rack of the dishwasher. Try to find a container that can hold at least 1 cup of vinegar for this process, but heavily scaled dishwashers may require 2 cups of vinegar or multiple rounds of cleaning.
Next, simply start a regular cycle. When the cycle is complete, repeat the procedure with more vinegar if necessary. Otherwise, let the dishwasher air out with the door open to disperse the vinegar smell. If the smell is quite strong, consider running a second cycle with no vinegar to rinse out the dishwasher before you start washing dishes in it again.
For Tough Limescale in Dishwasher
Limescale that has been building up for quite some time may require pretreatment. Run a short cycle to get the dishwasher wet, and then shake baking soda all over the dishwasher. Work it in with a scrub brush if desired. Then add the container with vinegar and run a regular cycle.
If you really can't stand the smell of vinegar, mix lemon juice with the vinegar to create a slightly more pleasant scent. The citric acid in lemon juice acts as another good cleaning agent.
In the event that these natural remedies don't adequately descale your dishwasher, you can purchase commercial products for this task. Take care to only use food-safe products. For example, Finish dishwasher cleaner is specially made for dishwashers, whereas Lime-A-Way is unsafe for any food surfaces. Always read the labels before use.