Scale buildup in a hot water heater consists of minerals, mainly calcium and magnesium. Many professionals recommend draining a hot water heater periodically to get rid of scale buildup because, left unchecked, it decreases the life and efficiency of a hot water heater.
Scale buildup in the bottom of a hot water heater forms an insulating layer between the heating element and the water, causing the heating element to run hotter and longer than necessary. This increased heat shortens the lifespan of the steel casing and glass lining near the bottom of the heater, causes the heating element to burn out, and it increases the quantity of electricity needed to heat water in the tank. The sediment can also block lines, valves and drains and can sometimes cause noise as water trapped in the sediment turns to steam bubbles that build up until they are suddenly released.
Water softeners reduce sediment buildup in hot water heaters, but they can also consume the anode, leading to premature rust in the heater. Running the heater too hot can aggravate scale buildup because at higher temperatures, more minerals are forced out of the solution phase and end up depositing elements inside the heater.