Hard water and dishwashers: salt, settings and cloudy glasses
By Limescale Logic · Updated 8 October 2026 · Editorial policy
White marks after a wash do not automatically mean you need a household water softener. Start with the dishwasher's own settings and maintenance. Many machines have a built-in softening system, but it needs the right hardness setting and the correct salt.
Find your supplier's hardness value, then use your exact model's manual to set the dishwasher. Check the salt compartment and rinse-aid instructions separately. A tablet labelled “all in one” is not a reason to ignore the model's instructions.
Salt, detergent and rinse aid do different jobs
| Product | Purpose | Check |
|---|---|---|
| Dishwasher salt | Supports regeneration of the built-in softener. | Use the dedicated reservoir and approved dishwasher salt. Check the cap is secure. |
| Detergent | Cleans the load. | Follow dosage and programme instructions. Never put detergent in the salt reservoir. |
| Rinse aid | Helps the final rinse and drying. | Use the manufacturer's setting and refill guidance. |
Bosch's salt guidance specifically warns against replacing dishwasher salt with table, sea or kosher salt. This is a product-care instruction, not an invitation to add salt to the wash itself. Other models may have different arrangements; look for a reservoir in the manual before trying to fill one.
Set hardness using the correct unit
Record the value and unit from your water supplier. A result written as mg/L calcium carbonate is not the same number as German degrees. Use the hardness converter if necessary, then match the result to the table in your manual. Button combinations and setting codes vary between models.
If a whole-house softener already feeds the dishwasher, check the water reaching that appliance rather than assuming it matches the untreated supplier value. Ask the installer which outlets are softened and follow the appliance guidance when changing its settings.
Work through the residue in order
- Check the basics: confirm the hardness setting, salt level and securely closed salt cap. If salt was spilled during filling, follow the manual's clean-up instructions.
- Check the wash: clean accessible filters and spray arms as instructed, avoid blocking spray-arm movement and use the correct programme and detergent dose.
- Check drying: look at rinse-aid settings and whether water collects on particular items or loading positions.
- Check the glass itself: record whether the film washes away by hand or remains. Persistent cloudiness can need a different explanation; repeated descaling is not a diagnosis.
For descaling, use a treatment and procedure approved for the machine. Do not transfer a kettle recipe to a dishwasher or mix cleaning products. Bosch's white-film advice includes checking the built-in softener, rinse aid and descaling, but your own model's instructions govern quantities and timing.
What to tell a repair service
Before calling, note the model number, hardness value and unit, current setting, detergent, salt and rinse-aid products, and when the problem began. Photograph the residue on an item and any warning indicator. State whether the problem affects the whole load or only certain glasses. This gives the service team more useful evidence than “the water is hard”.
A leak, electrical fault or repeated error code belongs with the manufacturer's support service. Follow its instructions for stopping use. Do not dismantle the water-softening assembly yourself.
For scale in other appliances, see managing limescale without a softener. For repeated scale across the home, start with a supplier hardness check.
Sources and scope
Source guidance checked 8 October 2026. Manufacturer examples apply to the named products and do not replace your own model's instructions. This is a researched guide; no hands-on product test or individual medical assessment is claimed.