Nine contractors have secured a share of up to £3.5bn of work for Thames Water.
The utility giant signed deals with the companies that will deliver capital investment programmes as well as network and developer services over the next five years.
Thames Water said its Asset Management Period 6 work would be delivered by two alliances, each made up of two teams.
Eight2O – consisting of Costain/Atkins and Skanska/MWH/Balfour Beatty – will take on up to £2.5bn of work between 2015 and 2020.
Agility – made up of J Murphy & Sons/Morrison Utility Services and Kier/Clancy Docwra – won a potential £1bn of work over the same period.
Both alliances could have their contracts extended.
Thames Water chief executive Martin Baggs said: “The alliances will change the way we work and change the mindset. It’s fantastic to have a team that’s all working together, focusing on our priorities of health and safety and customer service. Problems will be problems for all of us but we’ll share the benefits as well.”