Thousands of gallons of water poured down Harborne Lane in Selly Oak after the pipe burst 6m (19ft 8ins) beneath the ground in November.
The road junction collapsed, taking a lamppost down with it and damaging 10 homes and trapping cars.
Severn Trent thanked people for their patience on a "long and difficult job".
Paul  Baldwyn, area operations manager for Severn Trent, said: "We absolutely understand the frustrations of those affected by the burst and the subsequent road diversion, and we know it has been going on for a long time, but we want to reassure everyone that we've been working hard on this constantly since the burst happened.
"It may have looked like there wasn't much being done on site to fix this pipe at times, but in fact there was lots of work going on in and around the city."
Resident Mel Rejayee described being stuck in the flood water in her car as "quite scary".
The road was closed from the roundabout at the junction of the A38 up to a petrol station near the junction with Quinton Road.
Severn Trent said more than 500 checks on pipes were required as part of the repairs.
A road has reopened, four months after a burst water main created a sinkhole and major flooding in part of Birmingham.