The Young-Lithgow pipeline, which is owned and operated by natural gas firm APA Group, had a leak caused by floods in the area earlier in the week.
Deputy Premier Paul Toole said the expected weeks-long disruption "could be potentially declared a natural disaster" that garners support from the federal government to cut-off households.
"Here in NSW this is a natural disaster that occurred from flooding. We will be pushing it up to the Commonwealth to seek assistance," he told reporters from Bathurst.
APA Group executive Gerard Coggan said the pipeline had a leak from the Macquarie River caused by the ferocity of the floods.
"It's a very significant weather event that has occurred and we'll wait until the waters go down so we can understand what happened," he told reporters.
Distributing the gas to households is handled by another company Jemena, which said the significant outage is going to test the patience of residents because it involves manually turning off metres and all appliances from ovens to showers.
"Given the number of customers impacted by the supply outage we expect this could take up to a number of weeks for all customers to be reconnected – it is a large scale and significant outage," the company said on Friday.
APA Group said on Friday that if the weather holds up customers can have their gas turned back on in Lithgow, Wallerawang and Oberon by early December.
"Subject to weather conditions not deteriorating and suitable construction conditions, we anticipate a permanent solution could see gas supply restored to consumers in Lithgow, Wallerawang and Oberon in approximately four weeks," the company told AAP on Friday.
It said temporary solutions such as trucking liquefied natural gas to the transmission line within 10 days are on the table.
A Jemena representative told reporters "we will be knocking on every single person's door that has gas, so please bear with us" in Bathurst.
Police personnel, council staff and State Emergency Crews along with 136 Jemena staff are tasked with the mammoth manual operation across the affected areas.
Mr Toole underscored how the repair process will take time and effort.
"They (Jemena) have to go to every house, to every business, turn off the gas and then make sure that entire section has the gas turned off," he said.
"Then they've got to purge the (pipe) line and make sure there's no air in the line, and go back to every individual residence and business to turn them back on, to make sure the community is safe so we don't see an explosion in a house."
"It's a tough time for communities at the moment."
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