Electric Water Heater Trouble Shooting Guide & Repair Information

How to trouble shoot your water heater and solutions of hot water heater problems

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This guide assumes that the hot water heaters were properly installed and were operating correctly before any problems developed.

Most electric hot water heaters have two thermostats, one near the top of the tank and one near the middle or bottom and are covered by removable metal cover plates. The thermostats are pressed firmly against the bare metal wall of the hot water heaters tank.

The top thermostat usually has a high limit switch that will trip if the water gets much too hot.  When it trips it shuts off the electricity to both the upper and lower heating elements.   If you need to reset the high limit switch there is almost always a red button that you press to reset the thermostat.  If the upper limit switch trips it is usually an indication that something else has gone wrong with the heater.  

Problem: Water heater not getting the water hot.

First after making sure the electricity is shut off to the heater, remove the upper thermostat cover plate and check the high limit switch button.  If it has tripped, press it to reset it.

Turn the power back on to the heater and check for power at the input terminals of the upper thermostat. (usually marked L1 and L2)  If no power is present then check your circuit breakers or wiring to the water heater.

If the hot water not getting hot then the upper thermostat should be applying power to the upper heating element.  Check for voltage at the upper heating element across the two terminals. There should be about 220 volts (if it is a 220 volt heater).  If there is power present at the heating element but the water is not getting hot then the heating element is probably burned out and  needs to be replaced..

No voltage reading across the element terminals at the upper heating element indicates that the upper thermostat needs to be replaced.

Problem: Not enough hot water or water temperature too low.

When the top of the tank is hot, the upper thermostat shuts off the power to the upper heating element and re-directs the power to the lower thermostat and lower heating element.  If the lower thermostat or heating element is defective, then the water in the lower portion of the tank will not get hot and the supply will be greatly reduced. You will quickly run out of hot water.

Check for power at the  upper thermostat terminals where the power is sent to the lower thermostat and heating element.  If there is no power then the upper thermostat should be replaced.  If there is power then check for power at the lower heating element.  If there is no power at the lower heating element then replace the lower thermostat.  

If there is power to the lower heating element then it should be getting hot.  If it is not, replace it. Another possibility is a broken dip tube. Check for a broken dip tube and replace if necessary.

Problem: Water is too hot.

Usually when the water is too hot, then it's usually a bad thermostat.  Check for voltage at the terminals of the top heating element.  If voltage is present at the top heating element, the top thermostat is most likely defective. If power is present at the lower heating element then it's the lower thermostat is that is probably defective.

Another possible cause of the water being too hot is if the thermostats are not making good tight contact with the wall of the tank.

Problem: TPR relief valve leaking.

The relief valve operates and releases pressure if either the temperature gets too high or if the pressure rises to an unsafe level. 

If the water heater inlet is connected directly to the main with no pressure relief valves or check valves between them then the expanding water simply flows back toward the main, and no pressure rise occurs.

If however there is no path for the water to escape, then the increase in water volume has no where to go and the pressure will increase dramatically, causing the pressure relief valve to operate. Placing an expansion tank near the inlet will give the increased volume someplace to go and eliminate the operation of the relief valve.

Another possibility is that the City water pressure has increased for some reason above the setting of the relief valve.

Problem: Popping or banging noise from the gas water heater.

Scale can build up on the heating elements causing all sorts of noises to occur while the elements are on. Remove the elements and inspect them. If the heating elements have a large buildup of scale on them then replacement is probably advised.

Problem: Stinky hot water.

Certain types of bacteria can react with the magnesium anode rod resulting in a rotten egg odor. Clean the tank using chlorine bleach or change the anode rod to aluminum one, an this will usually solve the problem.

Leaking tank.  

Replace the electric water heater.