The hydraulics of a hydraulic system depend on the type of fitting and the flow of fluid through it. When you tighten a fitting, you're changing the pressure (and therefore the flow) of fluid through the system. This is done by applying pressure to one side of the fitting and allowing fluid to flow past it into another part of the system. The amount of pressure that's applied to one side will determine how much fluid will be able to pass through that particular hole in the fitting
