A base plate for a self-propelled robotic cleaning apparatus for cleaning a submerged surface of a pool or tank. The base plate includes a bottom surface and a water inlet formed therethrough, and an inlet extension member configured to mount in the water inlet. The inlet extension member is slidably retractable and extendable in a direction that is normal relative to the bottom surface of the base plate. A height adjustment mechanism is coupled to the inlet extension member and configured to move the inlet extension member upwardly and downwardly in the normal direction relative to the bottom surface of the base plate. The height adjustment mechanism can be adjusted manually. Alternatively, at least one sensor is operably coupled to a controller to automatically control the height adjustment mechanism.