Pool cleaning method and apparatus

A method for cleaning the bottom of a pool uses an automated programmed pool cleaner capable of reversing movement and turning that is initially placed at an arbitrary location on the bottom of the pool and moved in a forward direction until it encounters an upright pool wall; the unit is reversed until it is a first predetermined distance from the wall, turned through a predetermined angle less than 180° and advanced until it again encounters an upright wall; these steps are repeated until the unit has encountered upright walls a predetermined number of times, after which the first predetermined distance is changed to one or more subsequent predetermined distances. All of the previous steps are repeated until all or substantially all of the pool has been cleaned. In a preferred embodiment, a rectangular pool is cleaned by setting the turning angle to 90° and the number of turns before changing the predetermined distance to seven. In another aspect of the invention, the unit has a rotary impeller driven in a horizontal plane, and the robot is turned by interrupting motive force to the impeller a plurality of times during a predetermined period of time to create a sufficient torque or torsional force to rotate the nearly neutrally buoyant unit through the desired turning angle.