Repairing a gas water heater begins with investigating the installation of the water heater. If the installation was performed correctly and the unit was operating correctly before any problem arose, then the problem must be attributed to another cause. The next step is to check the area for a gas odor. If a gas odor is present, immediately call the gas supplier and have them check for leaks.
If the problem is no hot water, begin the investigation by removing the inner and outer burner access covers. Now check the pilot light, is it lit? If it is not, attempt to re-light it following the instructions provided with the water heater. If the pilot will not re-light, check with the gas supplier, getting them to diagnose and fix the problem, which could be a clogged pilot light line or gas not reaching the water heater.
However, if the pilot light does not stay lit when releasing the gas valve control, the problem could very well be a defective thermocouple or even a loose thermocouple connection to the gas control valve. To remedy this situation, tighten the thermocouple connection to the control valve and if that does not work, replace the thermocouple. Another reason for the pilot light not staying lit could be a draft blowing it out. Make sure the burner access cover is in place to prevent this problem.
If the pilot is lit, check to see if the control valve knob is set to “on” and not set to “pilot”. If the control valve knob is set correctly, then turn on a hot water tap and allow the water to run for several minutes. While the water is running, check the burner and see if it comes on. If it does not, let the water continue running for a while longer and if the burner still does not come on the problem is probably a defective control valve or thermostat. Replace the defective control valve or thermostat to solve the problem.
If the problem is insufficient hot water, the solution may be as simple as checking the thermostat setting, which may be set too low. If that is not the problem, check for leaking faucets. If leaking faucets are not the problem, the dip tube may be broken or may have fallen off allowing incoming cold water to be drawn out through the hot water outlet. Other possibilities to this problem are clogged burners and low gas pressure which would both require professionals to fix.
If the problem is slow hot water recovery, the culprit could be sediment buildup in the bottom of the heater. For this problem, flushing the water heater may be the solution. Other possible causes for slow hot water recovery could be insufficient combustion air caused by insufficient ventilation or improper burning operation, which once again would require professional attention.
If the problem is a discharge from the relief valve, the water temperature or the pressure getting too high could be causing it. An expansion tank installed in the line at the inlet will give the increased volume of water a place to go before causing problems with the relief valve. One last possibility could be the City water pressure has changed, rising above the setting of the relief valve. Installing the expansion tank can also solve this problem.
If the problem is banging or popping noises, a scale build up on the bottom of the tank could be the reason. This build up can cause all sorts of noises and is easy to remedy. Simply flush the tank to clean it.
If the problem is odors, bacteria that react with the magnesium anode rod could be causing them. Usually cleaning the tank with chlorine bleach or simply by changing the anode rod to an aluminum one solves the problem.
If the problem is a leaking tank, nothing short of replacing it will solve the problem.