The harder the water, the greater the amount of sediment. In a gas water heater, the sediment forms an insulating barrier between the water and the flame, slowing the heat transfer. The resulting overheating of the tank bottom can cause two problems. First, the glass lining starts dissolving at 160 O F, exposing the steel bottom to water and rusting. Second, severe overheating can weaken the steel bottom, possibly causing deformation.
Sediment can cause additional problems.
It can insulate the bottom of the tank from the protection of the anode rod. In addition, the sediment may host harmful bacteria. Also, sediment can be the cause of noisy water heaters when the bottom of the tank over heats and the water boils. Finally, the sediment can cause odor problems. Drain the tank regularly to remove sediment.