About 6 days ago, we suddenly only had luke warm water from all our hot water faucets. I called the hot water heater help line and they sent me a new thermostat. I had a friend (who is a pro) install the thermostat, and still no hot water. I can see the pilot is lit. I can hear a constant "roar" from the heater, which is supposed to be indicative of a build up of minerals and sediment in the tank, however none was noted when the t-stat was installed, and the tank was flushed at that time. The "tube" leading to the old t-stat was filled with gunk, so we assumed that was the problem. But still no hot water.
My tank is an energy saver, and is about 3- or 4 years old.