The permanent valve closes when the air is bleed from the compressor head. The air compressor check valve compressor is installed through a threaded connection, which is quick and easy to install without tools. With a detachable design, the interior is very convenient to clean and more durable. This one-way check valve can withstand high temperature and high pressure. Therefore, it can be a good replacement for old or damaged air compressor check valves. It is an excellent choice for air compressor accessories. The check valve adopts three-way external thread design, which has the characteristics of pressure resistance, corrosion resistance, high performance and reliability, and strong sealing performance. Three male connections are used for air hose connections. Two female connections are used for pipe connections and another male connection is used for air pressure vessels and compressor piston pumps. If the compressor check valve is not closed when the compressor is shut down, the compressor check valve must be replaced to allow air to flow back into the compressor head. This check valve is suitable for thread G1/2*3/8*10=20*16*10mm. It can be used for inline machine 2.5-3-4-5P small piston air pump and oiled piston air compressor.