The Southwest Regional Water District was originally organized as the Southwestern Butler County Water Association, a not-for-profit rural water cooperative, in 1968. The original system consisted of a 2.3 mgd water treatment facility and a distribution network of 160 miles of water mains providing water service to approximately 2,800 users.
In 1976, the Southwestern Butler County Water Association merged with the Oxford-Milford Water Association, another rural water cooperative, adding 340 users and 42 miles of water mains to the then existing system.
Between 1978 and 1981, the water system added 150 miles of water mains to serve an additional 1,100 users. The treatment facility was increased to a 3.6 mgd plant. Also, during the period, the Southwestern Butler County Water Association changed its name to The Water Association.
From 1981 through 1991, the Waterworks System continued to expand at a modest rate adding approximately 2,000 customers.
In 1992, The Water Association began a $3,000,000 improvement project consisting of 15 miles of transmission mains, the construction of 4 elevated storage tanks, 1 clearwell (finished water) tank, as well as related booster stations and solenoid control valves. At the conclusion of the project, the Waterworks System consisted of over 470 miles of water mains and 18 water storage tanks, providing water service to much of western Butler County, portions of southern Preble County and portions of northern Hamilton County.
At the request of The Water Association’s Board of Trustees, the Butler County Commissioners petitioned the Court of Common Pleas to create a regional water district. The Water Association’s Board of Trustees believed a regional water district could better serve the needs of the residents of western Butler County because it could borrow money needed for projects on a tax-exempt basis. With the cooperation of the County Commissioners, The Water Association transferred all of its operations to the newly created District, effective September 1, 1992, and once again changed its name to the Southwest Regional Water District. The District currently provides water to a population of approximately 43,366 people.