Off-line hydraulic filtration systems are used to filter hydraulic system fluids when adding new fluid, changing fluid, or flushing the hydraulic system before adding new fluid. While in-line hydraulic filters are integrated into the hydraulic system, off-line filtration is independent of the hydraulic system, allowing it to be used with multiple systems as needed. Clean hydraulic fluid reduces contaminant buildup and maintenance costs and extends the working life of the system. An integrated filter element can be changed when it becomes dirty or clogged. Off-line systems are used with industrial hydraulic systems, such as those found in automobile manufacturing and process engineering. Filtration carts are mounted on wheeled units to make it easier to move around the facility. Handheld filtration units have a handle for carrying.