Everyone thinks that the hot water heater in your home is a simple piece of equipment, often ignoring the hidden dangers that they can pose.  An improperly installed water heater is literally a bomb waiting to cause an explosion in your home.  At the top or on the side of the heater there is a pressure relief valve (see picture below).  This valve is designed to open in the event that the thermostat or control valve in the heater malfunctions.  If either of these fails, the elements many continue to heater the water past the usual 125-130 degree range.  As the temperature of the water increases, so does the volume.  The water pressure in a typical home system is somewhere between 40-60 PSI.  Are you getting the picture, temperature increases, volume increases, pressure increases and BOOM!!  Even in the event that the heater would not explode, you could have a “super-heated” water phenomenon on your hands.  When water is heated past the 212 degree mark (boiling) it becomes “super-heated”.  Turn on a faucet with super-heated water; it is going to vaporize instantly, very probably causing some very nasty steam burns.  By now, you now that everything in your home requires some form of maintenance.  You should annually open the pressure relief valve to ensure proper function.  Water should then come out the drain line at the bottom of the heater.  When the valve is closed; no more water should come out, if it does, even a small amount, have the valve replaced as soon as possible.  If you are uncomfortable doing this yourself contact your local plumbing professional to have this maintenance done, along with a hot water heater flush to remove any sludge build up that may have occurred over the year.