Shut It Off
Whether you drain the tank or not, you can shut the gas and extinguish the pilot light. Left on, the hot water heater would burn out if it developed a leak and the heat was on.
Shut Off the Water
If you're concerned about a flood, you can shut off the water supply to the heater. The worst thing that can happen is that the 45 gallons in the tank will leak out.
Is Your Heater Leaking
If your hot water heater is leaking, it must be replaced. Putting it off is asking for trouble.
When You Get Home
If you're looking forward to a hot shower when you come back from vacation, you will have to be patient.
Relighting Your Hot Water Heater
Most hot water heaters have instructions for lighting the pilot light on the side of the tank. It will take about an hour for the water in the tank to heat up. Remember to turn on the water supply.