To descale a dishwasher, empty it completely, pour 2 tablespoons of citric-acid descaler concentrate into the bottom of the tub, and run a full hot cycle with no detergent and no dishes. That dissolves the calcium carbonate on the heating element, spray arms and sump that detergent cannot remove. Do it monthly, or more often on hard water.
A dishwasher that leaves film on glassware, smells stale or has stopped drying properly is usually scaled, not broken. Hard water plates calcium carbonate onto the heating element, the spray arm nozzles and the sump. The element heats less efficiently, the nozzles clog, and food residue gets trapped in the scale, which is where the smell comes from. Detergent is alkaline and does not touch limescale. An acid does. Our dishwasher descaler is a 32% citric acid liquid concentrate with 1.5% lactic acid, 33.5% total acid, and it dissolves the scale rather than masking the smell.
What you need
- Think Crucial Dishwasher Cleaner and Descaler (32% citric acid, 15 uses, 16 fl oz). Works in Whirlpool, Bosch 300, 500 and 800 series, KitchenAid, Samsung, LG, GE, Frigidaire, Maytag, Amana, Kenmore, Miele, Thermador and any standard dishwasher that accepts a liquid cleaner.
- Miele owners can also use the Universal Descaling Concentrate for Miele appliances (35% citric acid, 30 uses), one bottle for the Miele coffee machine, steam oven, washer and dishwasher.
- A tablespoon measure.
Steps
- Empty the dishwasher. Take out every dish, the cutlery basket and anything on the racks. The acid needs to work on the machine, not on your plates.
- Pull and rinse the filter. Twist out the filter assembly in the floor of the tub and rinse it under the tap to clear food debris. Refit it. This step is not in the bottle instructions but it means the descaler is dissolving scale instead of fighting through debris.
- Add the descaler. Pour 2 tablespoons of concentrate into the bottom of the tub. Not in the detergent dispenser, not in the rinse-aid reservoir; straight into the tub floor so it is in the wash water from the first fill.
- Run a full hot cycle. Choose the hottest, longest normal cycle. No detergent. No dishes. Let it run all the way through, including drying.
- Check the result. Open the door. The tub, element and spray arms should be clean and the stale smell gone. If scale was heavy, run a second cycle with another 2 tablespoons.
- For Miele dishwashers using the Universal Descaling Concentrate: add 1 tablespoon of concentrate, top up with water as the Miele instructions specify, run the machine's own descaling program, then run its rinse cycle before normal use.
How often to descale a dishwasher
Monthly is the baseline for most homes. On hard water, where glassware clouds within a week or two of a descale, every two to three weeks keeps ahead of it. On soft or softened water, every two months is enough. A 16 fl oz bottle gives 15 cycles at the 2-tablespoon dose, over a year of monthly cleaning. If your dishwasher has a built-in water softener (common on Bosch and Miele), keep its salt topped up; that slows scale but does not stop it.
What not to use
- Bleach. It does not dissolve scale, it attacks stainless steel tubs over time, and it must never be combined with an acid descaler. Do not run bleach and citric acid in the same cycle or back to back without an empty rinse between.
- Vinegar in the rinse-aid dispenser. Acetic acid is weaker than citric on calcium carbonate, and the dispenser is not designed to hold it.
- Powdered descalers that do not fully dissolve. Undissolved crystals sit in the sump and the spray-arm nozzles. A liquid concentrate goes into solution in the first fill.
- Phosphate-based cleaners. Our formula has no phosphates, no EDTA and no borates, is biodegradable, and is septic safe. Phosphates are restricted in many states for a reason.
- Running the descaler with dishes in. The acid is food-grade, but it is doing a job on the machine. Keep the load out.
Frequently asked questions
Is it safe for a septic system?
Yes. The formula is four food-grade ingredients, biodegradable and septic safe, with no phosphates, chlorine bleach, EDTA or borates.
Will it fix the stale smell?
Usually, because the smell comes from residue trapped in hard-water deposits. The descaler clears the deposits and the residue with them. If the smell persists after two cycles, check the drain hose for a low loop holding standing water.
Can I use it in a Bosch 800 series?
Yes. The product is formulated for Whirlpool, Bosch 300, 500 and 800 series, KitchenAid, Samsung, LG, GE, Frigidaire, Maytag, Amana, Kenmore, Miele and Thermador dishwashers, and any standard dishwasher that accepts a liquid cleaner.
Why citric acid and not a tablet?
Tablets have to dissolve before they work, and they do not always finish dissolving in a short cycle. The liquid is in solution from the first fill. The lactic acid in the blend is a second food-grade acid alongside the citric.
Will it void my dishwasher's warranty?
Each manufacturer sets its own terms. Our descaler is a compatible product, not an OEM product, and using a non-OEM product may affect your warranty. Check your warranty before you decide.
Products used in this guide
- Think Crucial Dishwasher Cleaner and Descaler, 15 uses, 32% citric acid, 16 fl oz
- Think Crucial Universal Descaling Concentrate for Miele appliances, 30 uses, 35% citric acid, 16 fl oz
Whirlpool®, Bosch®, KitchenAid®, Samsung®, LG®, GE®, Frigidaire®, Maytag®, Amana®, Kenmore®, Miele® and Thermador® are trademarks of their owners and are used only to describe compatibility. Think Crucial is an independent manufacturer and is not affiliated with, endorsed by or sponsored by any of them. Our descalers are compatible products, not OEM products, and are not covered by those manufacturers' warranties; using a non-OEM product may affect your warranty. Always follow your dishwasher manufacturer's own cleaning instructions.