A control valve assembly for a single tank water treatment system of the type in which the treatment tank requires periodic regeneration, comprising: a) a valve housing having multiple levels (14a, 14b, 14c); b) a water usage metering mechanism located within said housing and operative to monitor the quantity of water treated by said treatment tank, said metering mechanism including a metering turbine that is operatively coupled to a metering disk by a gear train having a plurality of gears (336, 338), at least one of said gears rotating on a common shaft with said metering turbine; c) an inlet/bypass valve located within said housing and operative to communicate either a source of water with a tank inlet of said treatment tank or to communicate said source of water with a system treatment outlet whereby said tank is bypassed; d) a fluid pressure operated outlet valve for controlling the communication of an outlet of said tank with said system treatment outlet; e) a regeneration control mechanism cooperating with said metering mechanism to initiate and control regeneration of an exhausted tank, said regeneration control mechanism operative to communicate fluid signals to associated valve components mounted within said valve housing, one of said valve components being a control valve which is opened by a fluid signal from said regeneration control mechanism and controls communication of water to a regeneration control turbine and to a venturi, whereby brine solution from a brine reservoir is communicated to said treatment tank; f) said regenerating control turbine rotating in a direction opposite to the direction of rotation of said metering turbine; g) a brine control valve for controlling the communication of brine solution to said venturi communicating with said treatment tank, when said control valve is opened by fluid signals generated by said regeneration control mechanism; and h) a fluid pressure operated drain valve for controlling the communication of a treatment tank inlet conduit with an ambient drain. a) a valve housing having multiple levels (14a, 14b, 14c); b) a water usage metering mechanism located within said housing and operative to monitor the quantity of water treated by said treatment tank, said metering mechanism including a metering turbine that is operatively coupled to a metering disk by a gear train having a plurality of gears (336, 338), at least one of said gears rotating on a common shaft with said metering turbine; c) an inlet/bypass valve located within said housing and operative to communicate either a source of water with a tank inlet of said treatment tank or to communicate said source of water with a system treatment outlet whereby said tank is bypassed; d) a fluid pressure operated outlet valve for controlling the communication of an outlet of said tank with said system treatment outlet; e) a regeneration control mechanism cooperating with said metering mechanism to initiate and control regeneration of an exhausted tank, said regeneration control mechanism operative to communicate fluid signals to associated valve components mounted within said valve housing, one of said valve components being a control valve which is opened by a fluid signal from said regeneration control mechanism and controls communication of water to a regeneration control turbine and to a venturi, whereby brine solution from a brine reservoir is communicated to said treatment tank; f) said regenerating control turbine rotating in a direction opposite to the direction of rotation of said metering turbine; g) a brine control valve for controlling the communication of brine solution to said venturi communicating with said treatment tank, when said control valve is opened by fluid signals generated by said regeneration control mechanism; and h) a fluid pressure operated drain valve for controlling the communication of a treatment tank inlet conduit with an ambient drain.