Washing machines and dishwashers: match care to your water hardness

Water hardness can affect detergent dosage and encourage deposits inside a washing machine or dishwasher. The value is not the same in every part of Luxembourg, so the useful first step is to check the hardness for your own supply zone.

What you do next depends on the appliance. Its manual sets out the relevant settings, compatible products and maintenance schedule. The often-quoted range of 55 to 60 °C applies to a water heater or hot-water system; it is not a universal programme setting for a washing machine or dishwasher.

Check your local water hardness

Water hardness measures the amount of dissolved calcium and magnesium. In Luxembourg it is commonly reported in French degrees (°fH). The figure can vary between municipalities and between supply zones serving the same municipality. The Water Management Administration advises residents to ask their supplier or municipality for the local value.

This specific figure is more useful than a broad assumption about northern or southern Luxembourg. It helps you enter the correct hardness setting on a dishwasher and read a detergent dosing table. If the manual uses German degrees, the official FAQ gives the conversion: 1 °fH equals 0.56 °dH.

What limescale can change inside an appliance

When water is heated, some minerals can form deposits on parts that come into contact with it. The amount depends on water hardness, temperature, use and appliance design. Luxembourg's Water Management Administration says that very high levels of limescale can affect the operation of household appliances.

That does not predict a machine's lifespan or prove the cause of a fault. If an appliance stops heating properly, shows an error code, leaks or makes an unusual noise, consult its manual, the manufacturer's service team or a qualified technician.

Put the 55–60 °C guidance in context

The recommendation to keep hot water between 55 and 60 °C applies to a water heater or hot-water system. It is intended to balance hygiene requirements with limiting deposits in that installation. Comparisons of scale formation at 55, 65 or 75 °C also concern domestic hot-water systems, not a universal programme for household appliances.

For a washing machine or dishwasher, select the programme for the laundry, dishes and manufacturer's instructions. Do not change an internal setting or run an unusually hot cycle solely to tackle limescale unless the manual tells you to do so.

Adjust detergent and settings

Detergent dosing charts usually take water hardness and the level of soiling into account. Start with the stated amount and avoid overdosing: extra product can leave residues without correcting a limescale problem.

A dishwasher manual explains how to enter the water-hardness setting and when regenerating salt is required. A washing-machine manual lists any maintenance programmes. These model-specific instructions are more reliable than a fixed schedule or a product claimed to suit every machine.

Descale safely: what to do and what to avoid

Read the appliance manual before adding a descaler. Some manufacturers specify a maintenance programme or approved product; others warn against certain acids on seals, pipes or metal parts. There is no universal descaling product or empty cycle.

Follow the stated dose and contact time, never mix products, and complete the rinse cycle required by the manufacturer. Vinegar is not an automatic alternative: repeated exposure to acid may be unsuitable for some components.

A whole-house water softener should not be recommended from a general article either. Whether it is appropriate depends on the measured hardness, the plumbing system and advice from a qualified installer.

When to call a technician

Visible scale does not prove the cause of a fault. Switch the appliance off and contact its service team or a technician if it leaks, smells unusual, trips an electrical breaker, makes an unfamiliar noise or repeatedly displays an error code. Dismantling a heating element or adding an unapproved product can make the fault worse and affect the warranty.

Clean the surfaces around appliances

Visible marks around a sink, on taps or on a shower screen are part of surface cleaning. Check that the product is compatible with the material, particularly natural stone, metals and grout. Surface cleaning is not a substitute for technical appliance maintenance.

If you would like help cleaning your home, see Fast Clean's residential cleaning service. Repairs, dismantling and internal descaling of appliances remain the responsibility of the manufacturer, service team or a qualified technician. You can also read our guide to hard water in Luxembourg for more context on local figures.

Sources

• Water Management Administration, Luxembourg — Drinking-water FAQ: eau.gouvernement.lu (accessed August 10, 2026).
• data.public.lu — Tap-water hardness data: data.public.lu (accessed August 10, 2026).
• ecoconso — Information on water hardness: ecoconso.be (accessed August 10, 2026).