Cost-benefit analysis and engineering analysis were used to help New Castle County, Delaware, decide if it should acquire the major private water companies which serve the northern part of the county and then enter into a joint operation with the major municipal systems in order to achieve a unified, countywide water system. The present value of the quantifiable benefits resulting from unification are computed using alternative discount rates and time periods. These present values are compared to alternative costs of purchasing the private water companies on the basis of their capitalized earnings, original cost, replacement cost and fair value. In those instances where B/C > 1, the county could justify unification on the basis of its own benefits and costs subject to the caveat that many specified benefits and costs could not be quantified. Benefit-cost analysis provides a certain perspective, but it alone cannot decide the question of unification through public ownership.