Most homes feature either a gas or an electric hot water heater. Especially in the winter, these devices are invaluable in making sure that a home is inhabitable. However, they are also extremely susceptible to damage during this time of year, as the strain of getting water to an appropriate temperature is increased during cold spells.
Electric water heaters use either 120- or 240-volt power to energize heating elements that protrude into the water heater from the sides of the tanks. Usually, an electric water heater will have two of these elements within the tank to guarantee that the water never gets too cold. When the heaters aren't put to use during a given cold spell, they are prone to damage if the water within the heater eventually freezes.
These elements are placed at opposing ends of the tank - one at the top, one at the bottom. When the water in your home fails to get warm when you turn the faucet, this is usually a sign that the elements have both failed. If you notice irregularities in the temperature of the water in your home, however, it may be because one of these elements has malfunctioned and your heater isn't working at full capacity.
When you turn the faucet and the water gets warm but never really gets hot, it may be because the top element on the heater has given out. Since the water leaves the tank from the bottom of the heater in most models, this means that the cold water is traveling out first and the water that follows doesn't have enough support from a second heater to raise the temperature enough.
If the water comes out of the faucet and starts out hot, but eventually goes cold, you probably have the opposite problem, and should contact a Fairfax, Virginia plumber service to replace the tank.