A 15 mm swing non-return valve is a type of plumbing valve used to regulate the flow of fluids or gases through a pipe system. It is designed to allow fluid or gas to flow in one direction only and to prevent backflow, which could cause contamination or damage to the system.

The valve consists of a swinging flap or disc that is hinged to the valve body. When the fluid or gas flows in the forward direction, the flap or disc swings open to allow the flow, but when the flow reverses, the flap or disc swings shut to prevent backflow. The valve is typically installed in a vertical orientation, with the flap or disc positioned to swing upwards and allow forward flow.

A 15 mm swing non-return valve is typically used in residential and commercial plumbing systems for various applications, including irrigation, heating, and cooling systems. It is suitable for use with a range of fluids and gases, including water, oil, and air.