A medical fluid or dialysis system includes an auto-connection mechanism that connects connectors from the supply bags to dialysis cassette ports or cassette supply lines. The system provides for multiple, e.g., four, supply bags, which can be connected to a manifold of the auto-connection mechanism. Tip protecting caps that protect the supply line ends and cassette ports or cassette supply line ends are made to be compatible with the auto-connection mechanism. The auto-connection mechanism removes all the caps and connects the supply lines to the cassette. At least one roller occluder is provided that occludes the supply tubing prior to the tip protecting caps being removed. The roller occludes prevent medical dialysis fluid from spilling out of the supply lines between the time that the caps are removed and connection to the cassette is made.