underground water piping

I am running a cold water line from my house out to a barn (150 ft) which I want to work in both summer and winter. I am going to bury 1/2 flexible sprinkler house(funnypipe by Toro) with one barb splice fitting. At either end will be a fitting to connect to hose spigot shut-off valves. I will bury the line 3 feet below grade, but, what do I do for freeze protection when I run the pipe up thru grade to enter both the house and the barn? Some people have told me that there is a pressure regulated sprinkler piping valve that can be at the bottom of the turn going up that will automatically drain the line when I turn the spigot off at the barn, someone else recommended freeze valves (I don’t know what these are), someone else said to use heat trace tape (is that O.K. on plastic flex pipe?), and still someone else said to install an electrically controlled solenoid valve in the house which can be switched on/off at the barn and all I will need to do is turn the switch off and leave the spigot open at the barn and the line will drain. What is normal procedure for running cold water piping (that is needed for winter use) to out buildings so it won’t freeze?