How to Descale a Dishwasher and Prevent Limescale Buildup

Limescale is one of the most common causes of reduced dishwasher performance in Australian homes. It builds up on spray arms, heating elements, the door seal and the interior walls over time, reducing cleaning effectiveness, causing cloudiness on glassware and shortening the life of the appliance. Here's how to descale your dishwasher and keep it running cleanly.

What Causes Limescale in a Dishwasher?

Limescale — also called calcium carbonate — is a white mineral deposit left behind when water evaporates. All tap water contains dissolved minerals, but hard water has higher concentrations of calcium and magnesium, leaving more visible deposits. Sydney's water is considered moderately hard, which means limescale does accumulate over time in dishwashers used regularly.

Signs Your Dishwasher Needs Descaling

• White or chalky deposits on the door seal, spray arms and interior walls
• Cloudy or milky residue on glasses and cutlery after washing
• Reduced water pressure from the spray arms
• Longer cycle times or reduced cleaning performance
• A chalky smell inside the dishwasher between uses

How to Descale Your Dishwasher: Step by Step

Step 1: Remove and Clean the Filter

Before descaling, remove and rinse the filter under running water. Use a soft brush to remove food particles and grease. Rinse clean and replace. A clogged filter reduces the effectiveness of the descaling process.

Step 2: Check and Clean the Spray Arms

Remove the spray arms by unscrewing or unclipping them according to your model's instructions. Hold them under the tap and check that water flows freely from each hole. Use a toothpick or thin wire to clear any blocked holes. Rinse and replace.

Step 3: Run a Descaling Cycle

There are several effective methods:

Method A: Commercial Dishwasher Descaler
Products like Bosch Descaler, Finish Dishwasher Cleaner or Supercare Descaler are designed specifically for dishwashers. Place the product according to the instructions (usually in the base of the empty dishwasher) and run a hot cycle. These products are safe for all dishwasher components.

Method B: Citric Acid
Pour 200g of citric acid powder into the base of an empty dishwasher and run the hottest cycle available. Citric acid is an effective, food-safe descaler. Do not use citric acid if your dishwasher has a rubber door seal that is already cracked or aged, as acid can accelerate rubber degradation.

Method C: White Vinegar
Place a cup of white vinegar in a dishwasher-safe bowl on the top rack and run a hot cycle. This is less effective than commercial descalers or citric acid but provides light maintenance cleaning. Do not use vinegar regularly — frequent use can damage rubber components over time.

Step 4: Wipe Down the Door Seal and Edges

After the cycle completes, use a damp cloth with a small amount of baking soda to wipe the door seal, door edges and any areas not reached by the cycle. Remove any visible limescale deposits.

How Often Should You Descale Your Dishwasher?

For most Sydney households, descaling every 1–3 months is sufficient depending on water hardness, how often you use the machine and whether you use a rinse aid regularly.

How to Prevent Limescale Buildup

• Use rinse aid — rinse aid reduces water surface tension, helping water sheet off surfaces and reducing mineral deposits on glassware
• Use the correct amount of detergent — too little detergent allows mineral deposits to form more easily
• Use the salt dispenser on dishwashers that have one — dishwasher salt softens the water entering the machine, dramatically reducing limescale formation
• Run hot cycles periodically — high-temperature cycles help dissolve light deposits before they build up

Oceania Appliances stocks a full range of dishwashers from Bosch, Miele, Fisher and Paykel, Westinghouse and more. If your dishwasher is beyond cleaning and you're considering an upgrade, visit our showroom at 2/14 Centre Place, Wetherill Park or call 0400 983 352.