I have a gas water heater (not sure how old it is - it was installed by the previous owner). This morning I went to turn on the hot water in the shower and nothing happened. So I went to other sinks and showers and no hot water at all will come from any faucet. Cold water is fine at all locations. What could be the problem? I wasn't sure if the gas water heater had any safety features on it that would make it totally shut down if there were problems with it. Thanks for your help.

It sounds as though your hot water tank is off. If you paid the gas bill, there is gas, so it's mechanical (unless there is a problem with the gas supply.) There is a dial on the hot water tank. On older on models, it's near the floor. I had a newer one that had the dial up higher, on the side. Find it, and see if it has been moved out of 120 f range. Some have a "vacation" setting too. If you fiddle with the dial, there is gas to the unit and it still won't heat the water? It can take a while to get the water hot, but it should begin to feel warm within 20 minutes or so. If the water doesn't get warm, there may be something wrong with the tank.

Are you getting cold water or no water at all? Try the drain at the bottom. If you get a good stream of hot water, you have a blockage. A good place to check is the nipple at the outlet.

This is the response to labman:

I have no water out of the faucet when I turn on the hot water supply. Only water from faucet comes from turning on the cold water.

Either the water to the tank is shut off, or you have a blockage.

This is the response to labman:
I have no water out of the faucet when I turn on the hot water supply. Only water from faucet comes from turning on the cold water.
This is caused by a lack of maintenance on the heater. If you don't flush your heater on a regular basis minerals will build up on the bottom of the tank. When they build up so far they get sucked into the system and into your faucets where they clog the inle4t ports of the cartridges. Let m,e show you how to maintain your heater. For long life and fewer troubles you should keep your heater clear of mineral build-up by flushing on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back togather the same way you took them out. If you still can't get hot water pull the valve apart and clean the inlet ports on the cartridge. Now turn the hot water on for a moment to flush out the hot water supply and the valve body. Reassemble and test. Don't forget to flush it out every month. Your heater will thank you for it. Good luck, Tom