Tip-Locate water heater and smell for gas in the area. Look for any signs of leaking on the unit or around it. The area around the water heater should be free of clutter and combustibles. Examine the gas line connected to the water heater. The gas line should be black metal pipe, copper or a gas approved flex line. Galvanized pipe is not approved for gas usage. Check gas line for sharp bends, kinks, and damage. A gas shut off valve should be installed in close proximity to the water heater connection. A drip leg which is a tee fitting with a capped lower vertical piece of pipe beneath it, should be installed on the pipe. The connection line should connect to the middle of the tee fitting and then connect to the water heater. Drip legs collect sediment from the pipe preventing it from getting into the water heater burner and possibly causing damage. The thermostat should be intact and set on the middle setting or lower. Higher settings could cause burns. If a higher setting is necessary for the water heater to provide proper water temperature, then that is an indication of an issue with the water heater. Contact a licensed and insured plumber for corrective actions for issues found.
Do you know how to detect improper materials or installation in supply lines? Improper material installation and use for interior natural/propane gas and water supply