Dissolved minerals in the water that enters your house will often precipitate out of the water when it is being heated in the water heater tank. This will often result in the deposits (largely calcium) building up on the bottom and lessening the efficiency of gas and oil-fired units. The minerals can also coat the heating elements of electric tanks and cause these to work harder and burn out more quickly. If you have a fossil-fueled water heater (gas or oil) and there likely to produce a rumbling sound after the burners have been on for a while. Electric heating elements that are coated over may make a faint hissing sound. Tanks with mineral deposits should have drained and electric heating elements should be removed and cleaned.
The electric power has to be off before any efforts are made at draining electric tanks. If the heating elements are not covered by water, they will burn out instantly. Turn off the power to oil burners so they do not fire and close the gas valve or turn down the thermostat prior to draining fossil-fueled tanks.
The shutoff valve on the cold water supply line to the water heater should be turned off when it is being drained. Energy conscious people schedule draining a water heater after taking baths, showers, or washing clothes. They turn off the gas valve or the electric circuit breaker before using the hot water so that no unnecessary or wasteful heating takes place.
Once the fuel supply is turned off, a hose can be attached to the drain valve and lead to the floor drain or other lower elevation outfall. The water will often be reluctant to drain out because it is held in place by a vacuum. Tripping the pressure relief valve lever will allow air to enter the tank and help it drain more quickly. Doing this repeatedly will often stir up the mineral deposits on the bottom and help flush them out.
Once the tank has been drained, electric elements can be disconnected and removed. We suggest that homeowners make a sketch of the electrical connections so that they are able to reconnect them with ease.