The faults of the check valve include: the valve cannot change direction or the change direction is slow and the gas leaks. (1) Check valve cannot change direction or change direction slowly, which is generally caused by poor lubrication, spring stuck or damage, oil stains or impurities stuck in sliding parts, etc. In this regard, firstly check whether the lubricator is working properly; whether the viscosity of the lubricating oil is appropriate. If necessary, replace the lubricating oil, clean the sliding part of the reversing valve, or replace the spring. (2) After long-term use, the check valve is prone to wear of the valve core sealing ring,  damage to the valve stem and valve seat, resulting in gas leakage in the valve. At this time, the sealing ring, valve stem, and valve seat should be replaced, or the reversing valve should be replaced with a