What Scale Costs You

The water heater, without much competition. Heat is what drives minerals out of solution, so the heater takes the brunt — sediment on the tank bottom over the burner, or scale directly on electric elements.

Then anything with a moving seal. Shower cartridges, faucet valves, and toilet fill valves all rely on a clean seat, and mineral deposits are exactly what prevents that. A shower that has started dripping is often a scaled cartridge rather than a worn one.

Dishwashers and washing machines heat water internally and scale up the same way. Their performance drops off, they use more detergent to achieve the same result, and they fail sooner.

Ice makers, coffee plumbing, and any small-passage appliance are similarly affected, and tankless heaters most of all because their passages are the narrowest in the house.

Descaling fixtures and flushing the heater manages the symptoms and is worth doing. It does not change what is arriving at the house.

Treatment at the main line addresses the cause and protects everything downstream at once, which is why the arithmetic usually favours it if the water tests genuinely hard. We would test first rather than assume.