Bay Area water supplied from the Hetch Hetchy reservoir in Toulumne County remains unaffected in quality from the Rim Fire nearby.
"I can say today, I can say tomorrow that our water quality is the same as it was before the fire," said Harlan Kelly, general manager for San Francisco's Public Utilities Commission.
San Francisco Mayor Ed Lee also announed on Tuesday the city reached a critical milestone when it comes to restoring power to residents.
Two fire stations were offline at the height of the Rim Fire, which is now 75 percent contained.
All but one is back in operation, officials said.
Authorities were also concerned about ash from the huge fire. But after testing the water that flows to 2.6 million Bay Area customers, they feel confident the water is safe to drink.
View more in Cheryl Hurd's video report above.