To replace a hot water heater's heating element, disconnect the heater, drain the water heater tank, unscrew the old element, and install a new element in the place of the old one. Refilling the heater tank and reconnecting the unit completes this process.
Turn off the power to the water heater at the breaker. Remove the insulation and top access panel, then snap off the plastic safety cover, taking care not to touch the wires. Test the wires with a voltage tester to ensure that they are current-free.
To drain the water heater tank, disconnect the water supply to the heater, remove the kitchen faucet aerator, and open the faucet's hot side to let air into the tank so the tank drains. Connect one end of a garden hose to the drain valve, and run the remaining end to a lower place. Open the tank's drain pipe, and allow the tank to drain.
Detach the element wires, and unscrew the element from the heater with a water heater element wrench. Using your hand, screw the new element into the port previously occupied by the old element, and tighten the element with the wrench. Attach the element wires to the new element, shut off the drain valve, and turn on the water supply to refill the heater tank. Finally, turn on the power, and test the new element.