Check with your local building department for local building code requirements. The sacrificial anode is a metal rod usually magnesium or aluminum which helps prevent corrosion of the tank. Once the anode is gone the tank itself begins to corrode. The anode is screwed into the top of the water heater and can be replaced. Sometimes the anode is built into a special hot water outlet fitting.
Softened water can cause the anode to wear out more quickly.
The dip tube directs incoming cold water to the bottom of the tank, preventing pre-mature mixing of incoming cold water with the out going hot water. Without the dip tube it may be difficult to get hot water even when the tank is full of hot water. Sometimes the dip tube is curved at the bottom causing a swirling motion in the bottom of the water heater to reduce sediment buildup, or making it easier to remove the sediment through the drain valve. The water-heater dip tube delivers cold water from an external water source to the bottom of the heater. Perfection Corp. of Madison, OH, manufacturer of virtually all dip tubes used in the United States, produced an unknown number of defective tubes between 1993 and 1996.