Agility, comprising J Murphy & Sons and Morrison Utility Services, and KCD, comprising Kier Services and Clancy Docwra, were selected after a procurement process.
The alliance will start in April 2015 after a mobilisation period commencing in January 2015 and will run for about 15 years.
It features the full range of services, including clean water network repair, rehabilitation and maintenance and leak detection, apart from building new water mains.
The alliance will also feature the management of logistics and scheduling of programmes, as well as the development of customer and stakeholder services.
Thames Water managing director of wholesale water Bob Collington said: "Agility and KCD will join the Thames Water family, working alongside us and our other partners in eight2O, to deliver our AMP6 programme and beyond.
The AMP6 program includes the reduction of leakage and the service improvement.
Collington said the alliance and eight2O will jointly agree processes for work allocation based on "best customer outcome and cost".
Thames Water serves 15 million customers a day across London and the Thames Valley.
The company supplies about 2,600 million litres of tap water and removes as well as treats over 4 billion litres of sewage for 15 million customers.
Image: Thames Water’s AMP6 program includes the reduction of leakage and the service improvement. Photo: Courtesy of Kier Group plc.
