In short

Hard water means higher levels of calcium and magnesium salts. In dishwashers it causes white film and weaker cleaning and drying; in washers and dishwashers it scales the heating element. The fix: dishwasher salt (if your model has a salt reservoir) and rinse aid, regular cleaning programmes, and the right amount of detergent.

What is hard water?

Hard water contains relatively high levels of dissolved calcium and magnesium salts. When water is heated or evaporates, these salts deposit as a hard white layer we call limescale.

Hardness varies between areas and sources (mains, tanker, home filter), so the effect can differ between two homes in the same city.

Signs your water is hard

  • A white film or spots on glasses after the dishwasher.
  • White deposits in the kettle or on tap heads.
  • Laundry detergent foams less than expected.
  • White clothes look dull or feel stiff over time.

Effect on the dishwasher

The dishwasher shows it most clearly: white film on glassware, weaker drying, and scale on the heater and spray arms that can block holes over time.

Many Samsung dishwashers have a softener salt reservoir and a water-hardness setting. Setting it per your manual and keeping salt and rinse aid topped up makes a big difference.

White film can also come from too much detergent. If it wipes off with a little vinegar it’s usually limescale; if not, it may be etching of the glass itself.

Effect on the washer

In washers, limescale gradually coats the heating element, slowing heating and raising energy use, and in advanced cases it can be linked to heater faults. Detergent is also less effective, so you need relatively more.

Regular drum-clean programmes, and not running very hot washes unnecessarily, help reduce build-up.

Practical steps to reduce the effect

  • Dishwasher: set the hardness level and keep salt and rinse aid topped up.
  • Use detergent at the recommended dose — more doesn’t compensate for hardness, it adds residue.
  • Run regular cleaning programmes on the washer and dishwasher, adding appliance descaler per the manufacturer’s instructions.
  • Clean the dishwasher filter and the washer pump filter — scale plus food or lint makes things worse.
  • If you have a home water softening or filtration system, keep it serviced.

Guides related to this article

Dishwasher not cleaning Food residue or white film on dishes. Washer not heating Water stays cold on hot programmes. Dishwasher not heating Dishes cold at the end of the programme. Washer not cleaning well Stains or detergent residue on clothes.

FAQ

Can I use table salt in the dishwasher reservoir?

Not recommended — use dedicated dishwasher salt, as table salt may contain additives that harm the softener.

Do I need salt if I use all-in-one tablets?

It depends on hardness; with hard water tablets alone may not be enough. Check your manual and judge by the results.

Does limescale cause serious faults?

Its effect is mostly cumulative — weaker performance and higher energy use, and over time it may contribute to heater faults or blocked spray holes.