We had a new hot water heater installed 1-2 years ago. It worked great up until about 2 weeks ago, where we all noticed that it no longer was heating to the same temperature. I can continue to crank the heat adjustment up, but that makes me nervous that I'll end up burning my children if it suddenly snaps back. What is the best thing to do to start fixing this?
Flush it using the drain valve. Hard water deposits will settle out on the bottom, and impair the transfer of heat from the flame to the water.
If you are depending on the water heater thermostat to prevent scalding your children, you're not abnormal, but you're doing it wrong.
Use a tempering valve between the water heater and your hot water system. That way you can have the water heater set hot enough to kill unpleasant bacteria, and also have water that does not scald anyone.