During the 18th century, responsibility for water supply and waste water treatment was shared between local government and private companies. Suppliers of water treatment and waste water disposal each had different powers, charges and resources for investing in pipes. In the 19th century many councils acquired powers to purchase their local water company. By 1973, 29 river authorities covered England and Wales and a further 160 water supply undertakers and no less than 1,300 sewage treatment authorities existed. In 1973 the Water Act brought together the many water and sewerage companies in England and Wales into 10 water authorities, each responsible for water supply, sewage treatment and river protection within its area. Each was led by a board with representatives from local authorities and central government. Severn Trent Water Authority was one of those 10 authorities. By the mid-1980s, however, the government had decided to privatise the water industry. This enabled the injection of much needed cash into the industry through loans and the issue of private shares. The 10 water authorities passed into private ownership in 1989.
1989 saw the formation of Severn Trent Plc, the parent company for Severn Trent Water. As a private company, Severn Trent Water invested heavily in replacing and repairing its assets and infrastructure. As well as complying with government legislation it set its own internal standards on issues such as public health, leakage reduction and the cleanliness of rivers and other water sources in its catchment region.
The group also began to build a products and services business in the United States beginning with the acquisition of Capital Controls Company in 1990. Since that time, Severn Trent Plc has built a portfolio of companies, known as Severn Trent Services. Severn Trent Services provides water and waste water treatment and operating services to utilities, municipalities and commercial customers.