Only if you're planning on turning off the heat, in which case you should drain all your water lines and put anti-freeze in the toilets. What I do when I leave for vacations is to dial the heat down to about 50 degrees, dial the hot water heater down to the "Vacation" setting, and turn off the main water valve for the house in the basement. I turn off the main water valve to avoid any catastrophies in case a pipe bursts while we're away (thinking of the washing machine, dishwasher, and outside faucets in particular).

Perfect answer above.

The only thing to add if you are totally winterizing and want to be "environmentally friendly" nowadays, they want us to use an RV antifreeze or a vegetable oil in ALL PTRAPS (sinks, washing machine drain),toilets, and floor drains.

You would also want to drain all water pipes, the water heater (shut gas) and even the toilet tanks themselves, right?

You would also want to talk to the city/town and see if they can remove the water meter, or even shut water off for the season you would be away.

If you have a water heat system, well, that's another story!

Anyway, as ebaines said so well, no need to drain the heater for a short vacation... just set the thermostat (gas valve) to vacation or pilot setting (for gas heaters) or shut off electrical breaker for an electric heater and you will be fine. When you return set the thermostat/breaker back to the old setting and hot water will be restored in an hour or so.

Mark