
During the design and construction of building sanitary facilities, the positive or negative pressure generated in the drainage system and the hydraulic pump phenomenon that occurs during the improper design or construction of the drainage and ventilation system cause the phenomenon of pushing positive pressure through the water in the bathroom, toilet, or drain on the lower floor.
				There are several design methods used to solve these pressure problems.  
				Black check valves are an economical solution to the problem of positive pressure (back pressure) in drainage and ventilation systems.
				
				
 
		 
		 
		 
		 
		 
		 
			Horizontal drain pipe (cross pipe)
 
			vertical drain pipe
 
			Convenient angle drain (horizontal)
 
			Convenient angle drain (vertical)
 
			Toilet backflow (Check Valve DN100A)
 
			Vertical drain (positive pressure) check 100A