Dishwasher water hardness: find the right units and setting
Start with a total-hardness result and the manual for your exact dishwasher. The same number means different things in different units.
A four-step setup
Find total hardness in your supplier report or a suitable home test. Note whether it is mg/l as CaCO₃, mmol/l, German degrees or Clark degrees. Convert it if necessary. Then use the matching row in your model’s manual to select the setting and follow its salt instructions.
A worked example, not a universal setting
A report of 264 mg/l as CaCO₃ converts to about 2.64 mmol/l or 14.78 °dH. You still need your manual: a setting number from another dishwasher, even of the same brand, may be wrong for yours. If the result sits near a boundary, ask the manufacturer which setting to use.
Salt, detergent and rinse aid have different jobs
Bosch explains that dishwasher salt supports the appliance’s water-softening system and that salt requirements depend on hardness. Follow the manufacturer’s guidance for the salt reservoir and your detergent combination. Do not substitute ordinary table salt or assume every tablet removes the need for a hardness setting.
Related questions
Hardness unit converter · Understand a supplier report
Check your published area information
Sources and review
Sources checked 6 September 2026. Prepared by WaterGrade.
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