Sediment in a water heater is not one single substance and hard water is not the only possible source. Mineral scale can form from dissolved calcium and magnesium, while sand, silt, corrosion products, and other debris can also contribute depending on the water supply and the condition of the system.
Heating can encourage some dissolved minerals, especially calcium compounds, to precipitate and form scale. The rate varies with water chemistry, temperature, usage, heater design, and treatment upstream of the heater.
Those effects do not translate into a universal percentage increase in energy use, a fixed loss of lifespan, or a guaranteed failure timeline. The actual impact depends on the appliance and the amount and type of buildup.
If you have hard water, confirm the level with a utility report or a hardness test rather than guessing from symptoms alone. Follow the water-heater manufacturer's maintenance guidance for your model. An older heater with an unknown service history, deteriorated valves, leaks, corrosion, gas concerns, or electrical faults should be assessed before maintenance is attempted.
Our maintenance context tool can help organize dates, hardness context, and observed changes. It cannot measure sediment inside the tank or diagnose heater condition.