Rain Bird 16AFDVC1 Sprinkler System Filtered Drain Valve, 1/2" Male Pipe Thread. This 1/2" male threaded valve unit automatically drains water from underground sprinkler systems after each watering cycle is complete. Install at a low point in your system to drain pipes after each use to prevent freeze damage to sprinklers and piping. Unique two-stage screening process prevents grit from siphoning back into pipes Plastic perforated cap screens out large particles; dispersion pad filters out small particles. Rain Bird “The Intelligent Use of Water".