A traditional tank water heater keeps water hot all day, and minerals in the water slowly settle at the bottom as sediment. That buildup can make the unit less efficient, cause popping or rumbling noises and, over time, contribute to corrosion inside the tank.

Common repairs include replacing heating elements, thermostats, gas control valves, thermocouples and pressure relief valves, which are often manageable costs. A leaking tank is a different story, since tanks usually can't be patched, and replacement typically means a larger expense plus installation. Rusty water, a damp floor around the base or hot water that runs out much faster than it used to are all signs worth checking soon.

Many manufacturers recommend flushing the tank periodically to remove sediment and testing the pressure relief valve. If you're not comfortable doing that, a plumber can handle it during a routine visit. Placing a drain pan underneath can also limit damage if a slow leak develops.