The very first thing to do when you have noticed that there is no hot water when you turn on your taps is to see if the pilot light in your Rheem hot water system has extinguished. Rheem hot water systems must be lit manually using the inbuilt piezo ignitor striker.
Knowing exactly how to light your pilot light is a handy skill to have as it is recommended to turn the pilot light off if you are going away for an extended period of time.
Turn the knob on your Rheem hot water system until it is in the off position.
Turn the temperature dial counter-clockwise until it is at the coldest temperature setting possible.
Wait for five minutes to allow any remaining gas to leave. Take the door of your Rheem system and turn the gas knob counter-clockwise until it is turned to pilot.
Push and hold the red button down, at the same time press the piezo ignitor striker (which is to the right) repeatedly until the pilot light is lit again. You will be able to see the pilot light through the window on the inner door. Keep holding the red button for sixty seconds after the light is lit, then let it go. The pilot light will stay lit now.
Place the heater door back again and turn the gas knob until it is on.