Hard water contains dissolved calcium and magnesium. When water is heated, some mineral scale can form on hot surfaces or settle in a storage tank. How much this matters depends on the water chemistry, heater design, temperature, usage and maintenance history.
Scale can reduce heat transfer, collect around heating surfaces and contribute to maintenance needs. In storage heaters, mineral deposits may become part of the material found at the bottom of the tank. In tankless heaters, scale can form in passages and heat exchangers.
Noise, reduced hot-water output, discolored water, leaks and higher bills are not proof that hard water or sediment is the cause. Those symptoms can have other explanations and should be evaluated in context.
Use the maintenance schedule and procedure in your heater's manual. Water hardness, model design and prior service history can change what is appropriate. An older heater with an unknown history or a deteriorated drain valve deserves extra caution before any flushing attempt.
A water softener reduces hardness minerals. A sediment filter removes suspended particles. They solve different problems, and neither should be treated as a universal requirement for every home.
Do not use a generic web procedure if there is a gas smell, active leak, damaged wiring, heavy corrosion, a stuck or deteriorated valve, or uncertainty about safely isolating and restarting the appliance. Follow manufacturer instructions or use a qualified service professional.
Use the maintenance-context tool to organize what you know about the heater. It does not measure sediment or diagnose condition.
If you want service help, 855-755-4920 may connect you with an independent third-party service provider or network. Tank Sediment is an informational website and does not itself provide plumbing services.