How to test water hardness at home

Find the published area result

Use your supplier’s postcode checker and look for total hardness expressed as calcium carbonate. Note the reporting period. A supply-area summary is useful context, but is not a test of the water at your tap.

Choose a hardness test, not a general score

For a home hardness kit, check that it measures total hardness, that its range includes the value you expect, and that its instructions state the units. Follow the kit’s sampling, timing and reading instructions exactly. Record the date, tap, result and unit. A hardness-only result cannot answer questions about lead, bacteria or overall drinking-water quality.

An example of reading the units

Suppose a total-hardness kit reports 15 German degrees (°dH). That converts to approximately 268 mg/l as calcium carbonate. This is an illustrative conversion, not a test result for your home. If a strip gives a colour band or interval, retain that range rather than turning it into a falsely precise number.

Use the result for your appliance

Match the unit to your appliance manual before choosing a setting. If the reading falls close to a setting boundary or differs greatly from the supplier report, repeat the measurement according to the kit instructions and contact the supplier or appliance manufacturer for help.

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