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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.
  • Some models (those with a letter ‘H’ in the model name) have a built in water softener.
  • Models with water softener are not currently available in New Zealand and Australia.
If your home has hard water and your dishwasher has no built-in water softener...
  • Follow the detergent quantity recommendations on the following pages.
  • If available, use a detergent with high phosphate content. Phosphate softens the
  • water and this improves wash results. If detergent with phosphate is not available, we recommend using multi-purpose tablets.
  • Use rinse aid. We recommend you raise the rinse aid setting to 5 to help improve wash performance. See quickstart guide for instructions.
  • Use a dishwasher cleaner/descaler regularly, or whenever you notice a build-up of limescale deposits in your dishwasher.

If your dishwasher has no built-in water softener and you live in a hard water area, 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 pages.
  • Ensure the drawer is not overloaded and water can reach all the dishes.
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