This tip originally posted in AllAboutHome.com:
When an electric heater has problems, suspect the heating elements, their thermostats, and the high-temperature cutoff. The two heating elements (upper and lower), immersed in water, are controlled by thermostats which, along with the high-temperature cutoff, are concealed behind a panel on the side (insulation must be cut away for access after removing the panel). If the high-temperature cutoff has tripped due to water that's too hot, the solution may be as easy as pushing the reset button. High voltage and inaccessibility warrant a service call to adjust the thermostats, reset the high-temperature cutoff, or to replace any of these components of the heating elements themselves.
There is no hot water.
Check for:Remedies:
- The heater has no power.
- The safety thermostat has quit working.
- Defective heating thermostat.
- Defective heating elements.
- Accumulation of rust, scale, or sediment in the tank or pipes.
The hot water supply is too low.
- Check the fuse box/ circuit breaker.
- If the heater repeatedly blows fuses call an electrician.
- Push the reset button.
- Test the heating thermostats and elements.
- Test the thermostats and replace if necessary.
- Test the elements and replace if necessary.
- Drain and flush the tank and pipes.
Check for:
- Thermostat is set wrong.
- The tank is too small.
- Heat is getting loose in the pipes.
- Defective heating element.
- Leaking hot water faucets.
Remedies:
- Turn the thermostat to a higher temperature.
- Install a larger heater.
- Move the heater nearer to the point of use if possible.
- Insulate the hot water pipes.
- Test the element then replace it.
- Repair or replace the faucets.
The water temperature is too high.
Check for:
- Thermostat is on the wrong setting.
- Inadequate insulation around the thermostats.
Remedies:
- Turn up the thermostat.
- Add insulation around the thermostats.
- Test the thermostat and replace if necessary.
There is a water leak.
Check for:Remedies:
- Defective gasket or seal on the element.
- Defective safety valve.
- The tank is rusted through.
- Leaking plumbing connections.
- Check and replace gasket or seal.
- Check and replace the safety valve.
- Buy a new water heater.
- Call a qualified contractor.
The heater becomes unusually noisy.
Check for:
- Accumulation of rust, scale or sediment in the tank.
- Scale has formed on the elements.
Remedies:
- Drain the tank and flush it out.
- Remove the elements, soak with vinegar and then scrape off the scale.
Your hot water pipe is rusty or discolored.
Check for:
- Accumulation of rust or sediment in the tank.
- Scale has formed on the elements.
- Corroded water pipe.
Remedies:
- Drain the tank.
- Remove the elements, soak them in vinegar and then scrape off the scale.
- Have a plumber replace the pipes.