Abstract: Water supply apparatus for a lithographic printing machine includes a main frame having two laterally spaced main frame members, and a sub-frame having two laterally spaced sub-frame members each pivotally mounted on a respective main frame member. A laterally extending water transfer roller is rotatably mounted between the main frame members, a laterally extending water pick up roller is rotatably mounted between the sub-frame members, and a laterally extending pressure roller is rotatably mounted between the sub-frame members and in contact with the pick up roller, which projects into a water tray. The sub-frame can be pivoted to position the pick up roller in or out of contact with the transfer roller, and the main frame is attachable to a printing machine to enable water to be transferred from the transfer roller to a lithographic printing plate.