Free machine-care tool

Water Hardness & Descaling Guide Use your measured water, not a regional guess

Enter a supplier result or test-strip reading, convert common hardness units and see how the water should influence your machine setting, filter routine and descaling approach.

Check my water Find the hardness value
A better maintenance plan

Three steps from water result to machine care

01
Get a local measurementUse your water supplier, the machine test strip or a suitable drop test.
02
Set the machine correctlyWhere supported, the hardness setting helps determine when the descale alert appears.
03
Follow the model procedureUse the alert, filter schedule and descaling instructions for the exact machine.
Local supply zones varyA broad UK region is not accurate enough for a maintenance schedule.
Hardness is not TDSTotal dissolved solids cannot identify calcium and magnesium hardness by itself.
Filters reduce, not eraseA compatible filter may delay scale but still needs replacement and correct activation.
Cleaning is separateDescaling mineral deposits does not remove coffee oils or milk residue.
Convert and interpret

Turn a hardness reading into a care approach

The result does not invent a universal calendar. It classifies the water, estimates the incoming mineral load and explains how to use the exact machine’s hardness setting, alert and filter.

Your water and machine

The example starts at 180mg/L as calcium carbonate, around the moderately hard range.

Water result
litres
Include brewing, rinsing, hot-water dispensing and steam purging. This is used only to show relative incoming mineral load.
Your machine
Guidance updates automatically. Use the hardness of the water that actually enters the tank.
Water hardness classification

Moderately hard

This water carries a meaningful scale risk in heated equipment. Use the measured value to set the machine rather than relying on a broad regional label.

Converted hardness 180 mg/L as CaCO3
10.1°dHGerman degrees
18°fHFrench degrees
12.6°eClarke degrees
Primary maintenance trigger Set the machine’s hardness level accurately, then descale when it prompts.

Apply the result

    Machine-specific cautions

      Incoming mineral load

      At 0.5 litres per day, the incoming water contains the equivalent of about 2.7g of calcium-carbonate hardness per month. This is not the amount that will deposit as scale and is not a descaling threshold.

      Read the descaling guide
      Find the correct number

      Three better sources than a UK regional map

      Water can vary between supply zones and sometimes within the same city. Use the most local result available and retest after changing the water treatment.

      Most local mains result

      Water supplier report

      Find the company serving the postcode, then open its water-quality or hardness checker. Look for total hardness expressed as mg/L calcium carbonate, ppm, German degrees or French degrees.

      Find the water supplier
      Machine setup method

      Supplied test strip

      Some espresso machines include a strip and ask for the result during setup. Follow the strip timing and colour chart supplied with that machine rather than comparing it with another brand’s scale.

      Use the machine guidance
      Reusable measurement

      Hardness drop test

      A suitable aquarium or coffee-water test can give a more repeatable reading than a broad colour strip. Confirm whether it reports general hardness, carbonate hardness or total hardness before entering it.

      Check the hardness bands

      TDS is not a hardness result

      A conductivity or TDS meter estimates the overall dissolved-ion content. It cannot show how much of that total comes from calcium and magnesium, so it should not be entered as water hardness unless the supplier specifically reports the value as calcium-carbonate equivalent.

      UK hardness bands

      How the converted result is classified

      The calculator uses the Drinking Water Inspectorate’s calcium-carbonate bands. These describe the incoming water, not a universal coffee flavour target.

      0–100

      Soft

      Lower scale tendency, although very soft water is not automatically ideal for every machine or coffee.

      >100–150

      Slightly hard

      Some hardness is present and heated equipment can still accumulate deposits over time.

      >150–200

      Moderately hard

      Scale management becomes a meaningful part of normal machine care.

      >200–300

      Hard

      Correct hardness settings, filters where supported and prompt descaling become particularly important.

      Over 300

      Very hard

      High scale exposure. Use model-approved water treatment and do not ignore the descale alert.

      Water hardness is caused mainly by dissolved calcium and magnesium. It has no UK health-based maximum, but heating hard water can create limescale inside domestic appliances.

      Apply it to the machine

      Why one brand schedule cannot cover every model

      Manufacturers use different counters, hardness settings, filters and descaling programs. The exact model instructions remain the final authority.

      Manual or semi-automatic

      Keep cleaning and descaling separate

      Descaling treats mineral deposits in the water path. Basket, portafilter and supported backflushing routines remove coffee oils. Use only the circuits and chemicals permitted by the manual.

      Bean-to-cup

      Use the built-in program

      Set the water hardness correctly, activate a compatible filter where used and follow the machine prompt. Remove or replace the filter during descaling only when the model instructions say so.

      Capsule machine

      Follow the model’s descale mode

      Button sequences and rinse volumes differ. Use the approved process and avoid household vinegar unless the manufacturer explicitly permits it.

      Common maintenance mistakes

      Four shortcuts that can produce the wrong schedule

      The purpose of the hardness result is to configure and maintain the exact machine more accurately, not to replace its instructions.

      Assuming everyone in London has one hardness value

      Regional descriptions are broad. Use the local supply-zone result or test the water entering the machine.

      Treating a filter as permanent protection

      Cartridges need activation and replacement. Once exhausted or bypassed, the water entering the machine may be much harder than expected.

      Using vinegar as a universal descaler

      Acid type, strength, seals and internal materials differ. Use the product and dilution approved for the exact appliance.

      Descaling to fix coffee-oil bitterness

      Mineral scale and coffee residue are different problems. Complete the routine cleaning required for the brew group, basket and milk system as well.

      Useful next steps

      Use the result with the correct maintenance process

      Hardness tells you about scale exposure. The next guide should match the actual task: descaling, cleaning or diagnosing a flavour problem.

      Mineral scale

      Descale an Espresso Machine

      Prepare the machine, use the correct program and rinse the water path thoroughly.

      Read the descaling guide       Coffee and milk residue

      Clean an Espresso Machine

      Separate everyday cleaning, coffee-oil removal, milk care and descaling.

      Read the cleaning guide       Flavour diagnosis

      Espresso Troubleshooter

      Check whether an unpleasant taste is more likely to involve extraction, residue or water.

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      Frequently asked questions

      Water hardness and coffee-machine descaling

      The safest maintenance schedule is the one produced by an accurate hardness setting and the instructions for the exact model.

      Is ppm the same as mg/L for water hardness?

      When hardness is reported as calcium-carbonate equivalent in water, ppm and mg/L are normally used as the same numerical value for practical machine setup.

      Can I enter the reading from a TDS meter?

      No. TDS estimates all dissolved ions and does not isolate calcium and magnesium hardness. Use a supplier hardness result, machine strip or suitable hardness test.

      How often should I descale in a hard-water area?

      Set the machine hardness accurately and follow its prompt or model-specific interval. A broad regional calendar cannot account for the machine, filter, water use and exact hardness value.

      Does a water filter mean I never need to descale?

      No. A compatible filter can reduce scale formation, but it must be activated and replaced correctly. Some machines still require descaling after a number of filter cycles or when prompted.

      Can I use water from a domestic softener?

      Check the machine manual and the type of softener. Base-exchange systems replace calcium and magnesium with sodium, so softened water is not automatically the same as coffee-machine filtered water.

      Can I use vinegar to descale a coffee machine?

      Only when the exact machine instructions permit it. Several manufacturers advise using their approved descaler because household acids may damage parts or rinse poorly.

      Is descaling the same as cleaning?

      No. Descaling removes mineral deposits from the water path. Cleaning removes coffee oils, grounds and milk residue from the parts they contact.

      Why did the descale alert return quickly?

      The hardness setting may not match the water, the filter may not have been activated or replaced, the descale cycle may not have reset correctly, or the machine may be using more water than expected.

      Method note: unit conversions use 1°dH = 17.848mg/L CaCO3, 1°fH = 10mg/L CaCO3 and 1°e Clarke = 14.254mg/L CaCO3. Incoming mineral load is hardness multiplied by estimated daily machine water use and 30 days; it is not a measured scale deposit.