Hmmm... Re: Turning off the water...
Where? In our house, the shut off is in the utility closet... ( we have a crawl space underneath house.)
We call the city and have the water shut off at the street. In the case of a long term hard freeze, any part of the piping that comes from the city water main is vulnerable to freeze and bursting. This happened to us once when the shut off was in an unheated garage... the pipe burst and the garage flooded... fortunately with no serious damage.
The main shut off (at the street below the frost line) is usually a gate valve, which, over time, can leak, but still keeps the pressure down, and avoids serious flooding.
A small point on shutting off the water. Of course it means shutting off the HWH too. On coming back and turning the water on, we have had a problem in two houses.. relighting the HWH... The solution for us, when pressing the ignition button...to click (snap) the button multiple times quickly. Cost me a $80 service call to find the out... offered here, for free!
One more point on shutting down... Paid $4 for a thermostatically controlled electric switch that I connect to a desk light, set in the window facing my neighbors house. I set the temperature to 35 degrees, so that if the furnace goes off, the light will alert the neighbor.
Will keep the thermometer set at 50 degrees when we leave this year, instead of the 55 degrees in the past.