What kind of water valve ........

[Sedgehammer]

I want to put in a sprinkler system for our strawberry beds . They all slope down from each other . I need a valve that when the pressure is off it , opens . That way I don't need to worry about it freezing up . I'll be using 1.25 pvc I think

[PoginyHill]

I'm thinking you might consider a manually operated 3-way valve at the source of your water. When water is shut off to the sprinkler, it opens a path for the downstream pipes to de-pressurize. If you need a valve to open at the end of the system (to drain and not simply de-pressurize), then a fail-safe, normally open valve is needed. Some sort of restriction (such as a needle or flow control valve) is needed, so that when pressure is re-applies, the system will build pressure to close the normally open valve. Otherwise, the fail-safe valve will never close. You will probably need a drain valve for every low-point of your system.
I don't know where to get such a drain valve. Maybe a landscape supply house.

[sawguy21]

Frost free water shutoffs have the valve upstream in an area away from the cold, the pipe between it and the outlet slopes down so it drains. They are common here in the Great White North, check with a building or plumbing supply.

[Menagerie-Manor]

I want to put in a sprinkler system for our strawberry beds . They all slope down from each other . I need a valve that when the pressure is off it , opens . That way I don't need to worry about it freezing up . I'll be using 1.25 pvc I think

See if this can work for you.
Amazon.com : Toro 53740 1/2-Inch Sprinkler System Automatic Drain Valve : Lawn And Garden Sprinklers : Patio, Lawn & Garden

[firefighter ontheside]

Lowes has an auto drain irrigation valve

[Sedgehammer]

I should've included more info . This will be operating from a timer attached to a frost free hydrant . The irrigation line will be 6'6" above ground , so I can mow under it and people can walk unfettered while picking the berries . Will drive 7 , 8' t-posts in line with each other . Will weld a 1.5" , 1/8 angle to the top of the posts "V" corner down . The pvc will sit in the open v of the angle . This slopes all down hill . I just want a failsafe incase when I unhook the timer from the hydrant and I forget to open the ball valve on the low end , that there is a backup to drain the system . I will install the drain pointing down right below the ball valve 

@Menagerie-Manor I had seen those in my research , but was looking for something that looked like an actual drain , but that is what they are , just not what I was looking for in my 'mind' ..... Just goes to show me what happens when one thinks what something  should look like .  :D 

@firefighter ontheside Yup , that will work also

Thanks