Abstract: A modular modular control apparatus for a water treatment system which periodically undergoes a regeneration cycle including a backwash phase and a replenishment phase. The modular control apparatus has a modular design which includes interchangeable timer modules, a drive motor module, a drive mechanism, a valve cartridge unit, a brine valve module and interchangeable brine valve levers. The timer modules are rugged and relatively inexpensive but are not adjustable. Thus, to adjust the predetermined interval between regeneration cycles, a different timer module is installed. The drive mechanism includes two camming elements which in cooperation with an interchangeable lever and brine line sealing module draw a brine solution from the brine tank to replenish the treatment media and refill the brine tank with water to form a new brine solution. The use of interchangeable brine valve levers allows the quantity of brine solution used to replenish the treatment media to be easily adjusted.