A water treatment system provides treated water to a point of use by removing at least a portion of any hardness-causing species contained in water from a water source, such as municipal water, well water, brackish water and water containing foulants. The water treatment system typically receives water from the water source or a point of entry and purifies the water containing at least some undesirable species before delivering the treated water to a point of use. The water treatment system has a pressurized reservoir system in line with an electrochemical device such as an electrodeionization device. The water treatment system can have a controller for adjusting or regulating at least one operating parameter of the treatment system or a component of the water treatment system. The electrochemical device can be operated at a low current and low flow rate to minimize water splitting or polarization, which minimizes scale formation.