Note : Single acting cylinders can have 2 pipes. The second hose is connected in place of the breather and returns to the tank. This collects any leaks from the piston. It serves as drainage.
Checking the internal tightness of a single-acting cylinder is fairly easy, it starts to leak at the vent.
If the cylinder has a drain hose, simply disconnect it and check for leaks.
2- Double-acting cylinders
Here are the most common double-acting cylinders: