Abstract: A method for concentrating salt water. Salt water is separated from oil-water mixture which has been produced from a well. Salt water is introduced into a recirculating weir and mixed with more concentrated brine. Brine is recirculated through a thermal syphon apparatus. Recirculation includes passing brine, including some salt water, from weir into boiler vessel. Brine is heated within boiler vessel to a boiling temperature whereby brine, while boiling, generates steam which passes up out of weir. All of foregoing steps are performed at atmospheric pressure. The density of brine is sensed at a location in the lower vicinity of weir. Concentrated brine is released from lower vicinity when density at sensed temperature is at a level corresponding to a brine concentration near the precipitation of salt from solution. Salt water and brine is passed through a magnetic water treating unit. The concentrated brine, as released, is passed into a holding vessel.