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Fisher & Paykel Product Help

Water hardness and dishwashing

What is water hardness?

Hard water is water with a high concentration of minerals such as calcium and magnesium. In soft water, this concentration is low. Water hardness varies by geographical location.

How does water hardness affect dishwashing?

  • Hard water can be detrimental to the performance of your dishwasher. Over time, glassware washed in hard water will become opaque and dishes will become spotted or covered in a white film. Using very hard water can cause dishwasher parts to fail over time.
  • Naturally soft or softened water has no detrimental effects if used with the correct amount of detergent. However, excess detergent combined with hot, soft water may cause irreversible etching on glassware. Etching first appears as a rainbow-coloured film and—if allowed to continue—can make glassware permanently opaque.

What can I do to minimise any detrimental effects?

Contact your local water company to find out about water hardness in your area.

If your home has hard water ...

  • Increase the amount of detergent used.
  • Use a detergent with high phosphate content. Phosphate softens the water and this improves wash results. You could also try using multi-purpose tablets.
  • Use rinse aid. We recommend you turn the rinse aid on (CK models) and to at least setting 5 (CH & CHP models) to help improve wash performance.
  • Use a dishwasher cleaner/descaler regularly, or whenever you notice a build-up of limescale deposits in your dishwasher.

We recommend fitting a water softener to the household water supply. If the water hardness in your home is above 250 ppm/14.6 gpg, a water softener has to be fitted to maintain the performance of your dishwasher.
If your home has naturally soft or softened water...  

  • Avoid using too much detergent. Follow the quantity recommendations on the following page.
  • Ensure the dishwasher is not overloaded and water can reach all the dishes.
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