The outage is affecting residents in SE21, SE22, SE23, and SE26, who may experience low pressure or a temporary loss of supply.
The company first discovered the burst main on Lordship Lane on Monday evening (January 5) and dispatched crews to tackle the problem.
However, work was delayed due to road safety requirements and freezing weather, which have created a surge in burst pipes across the region.
The company confirmed that progress has been hampered by the need to implement road traffic management before repairs could safely begin.
In addition, icy conditions have slowed crews trying to reach affected areas.
Residents who require extra support during the outage are being urged to sign up for Thames Water’s Priority Services Register.
The company also warned that even once repairs are complete, it may take time for water supplies to return to normal.
Thames Water has said to provide another update by 9pm tonight (January 7) and continues to apologise for the disruption.
A spokesperson for Thames Water said: “We apologise for the continued disruption to your water service.
“Our repair team was unable to repair the burst water main earlier today.
“To ensure the work is carried out safely, we will be returning tonight to resolve the issue.
“Please be assured that this job remains a top priority, and we are doing everything possible to restore your water as quickly and safely as we can.
“Customers in the postcodes listed below may experience low water pressure or a temporary loss of supply while we continue working to resolve the issue: SE21, SE22, SE23 and SE26.
“We know how disruptive it is if you lose your water supply, and we appreciate your patience while these investigations continue.
“If you or someone you know needs a little extra support, our free Priority Services Register can help us to understand your situation so we can take it into account as best we can.
“We’ll provide another update by 9pm.
“Thank you for your patience while we work to resolve this.”
