Cast Brass Swing Check Valve 

Spring Loaded Clapper 
4" x 4" Grooved 
Used to prevent reverse water flow into Fire Protection Systems 
Applicable for vertical or horizontal installations 
1/2" tap and plug for added equipment such as a ball drip when paired with a fire department connection or a pressure gauge when used in a supply line. 
These check valves have a For use in standpipe and sprinkler systems UL listed FM Approved