The thing is some times they leave their garden hose on the faucet and then take it off later . then the pipes breaks in side the house just before the valve , the water in the hose backs up in the faucet and breaks the pipe and when you hook up to there house you then flood their basement . So what I do is I always have a cap. I first cap off the faucet turn it on and then listen for the sound of the water running . If I can hear the water running with the cap on , I know the pipe is broken. I always carry water in my truck. I hate doing a carpet cleaning job and then I have to do a flood job for free. I think 10 percent of the pipes here in Utah are broken
This is also in another post....cut and paste here also
Now operating a garden hose feed in this kind of weather gets really difficult, plus finding an outside hook up not very likely....and even those frost free hook ups we have had them being broken when we tap into them....
Homeowners make the mistake of leaving a garden hose hooked up too long, they freeze and then split back inside the home and you cannot see.
Anytime we hook into an outside water spigot we are very leery of what could be waiting for a flood inside the home and you will be blamed for causing it...even though you just avoided them being the first ones to hook up to it in the Spring and flood their home.
This frost free pipe cost me about $1000 or more about 5 years ago....plus ended up doing about $800 worth of work for free too. Home owner was there, asked if we could tap into here outside spigot and we were listening inside for any leaks....sure enough....busted from hose on too long....she freaked as we got water on the floor, 4 ceiling tiles got sprayed and we could have killed her pups in their kennels down there....

(cost was $375 to a plumber to replace and fix, air movers to dry out and time, and broke a
Punch bowl she had sitting on the steps as I rounded the corner going downstairs with airmovers....ugh...)
Then she asked me if I thought if she should worry about the spigot on the other side of the house too....Told her YES...WORRY!
But I am not testing it for her today!
So, we avoid tapping into anyone's water source....