A method and apparatus for microfiltration useful in softening water as well as in removing other dissolved constituents where the method comprises passing water that contains a precipitate through a semipermeable tubular membrane. Filtrate is received from the outside of the tubular membrane and the filtrate contains levels of dissolved compounds at concentrations below those that would be predicted by the solubility limits of the compounds. The method may be practiced at elevated pressures and turbulent flow without incurring significant fouling of the membrane. It is particularly suited to removing cations such as calcium and magnesium that contribute to water hardness. The water may be treated prior to passing through the membrane by adjusting pH, adding complimentary anions, or adding a flocculant. The apparatus comprises a series of semipermeable tubular membranes housed in a module. The membranes are fluidly connected to an inlet and two outlets. A momentary dynamic membrane is disposed on the inner surface of the tubular membrane.