Pilot light isn't lit

Carefully relight the pilot

Pilot light won't keep burning

Make sure the gas controls are completely turned on. Then, check and be sure it is firmly connected to the gas control unit and positioned near the pilot flame

Clog in the burner

Call a qualified professional

Defective thermocouple

Replace the thermocouple

Thermostat isn't correctly set

Turn the thermostat higher

Thermostat is defective

Call a qualified professional

Hot water pipes are exposed

Insulate the hot water pipes

Water Heater has no power

Check the fuse box/circuit breaker. If the heater repeatedly blows fuses, call an electrician

Safety thermostat has quit working

Push the reset button. Test the heating thermostats and elements

Defect in the heating elements

Test the elements and replace them if necessary

Thermostat is set wrong

Turn the thermostat to a higher temperature

Tank is too small

Have a qualified professional install a larger heater