Abstract: An integrated monitor and control system for continuously monitoring and controlling pH and free halogen concentration in swimming pool water is provided, comprising, in combination, a first electrochemical flow cell having two electrodes and through which swimming pool water flows, giving rise to an electric potential between the electrodes in proportion to hydrogen/hydroxyl ion concentration in the pool water; means for measuring the electric potential across the electrodes in a manner correlated with pH of the pool water; a second electrochemical flow cell having two electrodes and through which swimming pool water flows giving rise to an electric potential between the two electrodes in proportion to the oxidation/reduction potential of the pool water; means for measuring the electric potential across the electrodes in a manner correlated with halogen concentration in the pool water; a first operational amplifier in electric connection with the first cell and arranged to respond to a pH outside a predeterm