Hard water and scale: effects on appliances

Hard water carries dissolved calcium and magnesium that leave scale on heaters, valves, screens and spray arms. USGS classifies water as soft up to 60 mg/L (as calcium carbonate), moderately hard 61-120, hard 121-180 and very hard above 180. Knowing the local hardness helps explain repeat failures.

Cross-checked ~15 min easyBrands: All

Before you start

Use only descaling products the manufacturer allows; some acids damage seals and stainless parts

Diagnostic steps

Unlock all 3 steps with expected values

Full library + AI assistant for $34.90, one time.

Get lifetime access

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

More tech fundamentals guides

Component test · Fundamentals

How to test an NTC thermistor (temperature sensor) and read a resistance chart

NTC thermistors are used in refrigerators, dryers, washers, dishwashers, AC units and water heaters. Resistance falls as temperature rises. You test them by measuring resistance at a known temperature and comparing it with the chart for that exact sensor family.

7 steps ~20 mineasy

Component test · Fundamentals

How to test a water inlet valve (single, dual and triple coil)

Inlet valves are solenoid valves. Each coil opens one water path. Test each coil for resistance; a coil can be fine yet the valve still fail mechanically (clogged screen or stuck plunger), so check flow and the screen too.

6 steps ~20 mineasy

Component test · Fundamentals

How to test a PSC motor (common, start and run windings)

Permanent split capacitor (PSC) motors are used in AC condenser and blower fans, some washer and dishwasher motors. Test the capacitor first, then the three windings. The two individual readings must add up to the start-to-run reading, and nothing may read to ground.

7 steps ~30 minmoderate