Cut off valve on water heater ?

[David Nasser]

What is the name of this valve on water heaters?
And why do they have it cut off in some of the houses
that I inspect? (vacant homes)

I can always tell ...by very low pressure on the
hot water side of a faucet.

[Dale Duffy]

It's a Ball Valve to isolate water from entering the tank, I do not know why they have it turned off...is the Tank empty?

Home winterized?

[Bruce M. Graham, III]

is the power still on? have you seen any goofy looking guys hanging around? what does the tpr look like? http://dsc.discovery.com/videos/myth...igh-speed.html