The road has been closed to traffic since December 31 while crews worked to fix the damage and make the area safe.
The burst main initially caused road closures and water supply disruptions for residents.
The closure stretches between St Nicholas Road and Kashgar Road, with diversions in place for drivers and buses.
Bus routes 96, 99, 177, 180, 422, 469, and the N1 night service are affected.
Drivers and public transport users are being advised to allow extra time for their journeys.
The repair site is located at What3Words: home.latter.slope.
Thames Water apologised for the disruption and said it is working to reopen the road as soon as possible.
The site is expected to be completed on Sunday, January 5.
Further updates will be posted on the Thames Water website.
A spokesperson for Thames Water said: “We have been on site fixing a broken water pipe in Plumstead High Street since the 31st December.
“We have now completed our repairs and we will be re instating the road later today.
“Unfortunately, we’ve had to close the road to traffic (What3Words: Home.Latter.Slope) to keep everyone safe, we’ll keep diversions in place until it is completed.
“We aim to have the site cleared fully by Sunday Jan 5.
“If you’re travelling in the area, please add some additional time to your journey, We’ll keep updating this page regularly with our progress.”
