A leaking pipe on Woolwich New Road, near Tesco, is being worked on by Thames Water, Greenwich Council has said, adding that the work will probably be complete within five days.
Woolwich New Road is closed in one direction coming into the town centre, the Council said.
Woolwich residents have been complaining about the leak for some time, even as water companies face increasing criticism for failing to speedily fix leaks despite water shortages.
On Tuesday, the head of the water regulator for England and Wales told the BBC that most water companies were meeting their leakage targets.
