If you have a gas heater, and have no hot water (cold water still runs fine), then check the pilot light on your water heater. You should be able to find directions for operating the pilot light on your heater. For more assistance, call your local gas utility company. In many cases, they will send someone out free of charge to help you with this.
In many cases, especially with newer water heaters, you will have an electric ignition rather than a pilot light.
If you still have no hot water after ensuring that your pilot light is lit, you may need to turn up the temperature on your heater.
In the case that you still can’t get your hot water to work, give us a call so that we can send an experienced technician to take a look at your problem.