a double check valve is provided that includes an in - line inlet check valve and an outlet check valve that cooperate to prevent back flow of fluid through the valve . the check valve also includes at least one vent that allows for fluid trapped within the check valve to drain , thereby preventing freezing of the check valve and hydrant to which it is interconnected . the check valve provided omits many superfluous components and thus is smaller and easier to install than check valves of the prior art .