The water company has been investigating the issue in Hilden Road, Padgate, since yesterday (Saturday) afternoon.
Work to repair the burst, which has resulted in several homes being left with no water or low pressure, is continuing on Sunday morning.
But during its investigation, United Utilities also located a secondary burst at the junction of Montrose Close and Cinnamon Lane North, causing issues in Fearnhead and Cinnamon Brow.
A United Utilities spokesman said: “We’ve found the cause of no water or low pressure to be a leak on Hilden Road.
“For those impacted, we’re sorry for any inconvenience and we will have things back to normal as quickly as possible.
“We’re making progress with the repairs to the burst, but we still have some work to do. Due to the complex nature of the work our team have left site to collect some additional parts to complete the repair and will be returning this morning.
“We have also located a secondary burst on the junction of Montrose Close and Cinnamon Lane North which is still causing some issues with supplies in the area.
“Please be assured our team are working as quickly as they can to get this resolved.”