The Mythe water treatment works has been restarted and is due to begin feeding mains water back to the flood-hit residents of Gloucestershire.
Repair work went on at the works over the weekend
Significant progress had been made in repairing the flood-damaged works over the weekend, Severn Trent Water said.
Some 130,000 homes in Gloucestershire lost running water supplies after the floods hit more than a week ago.
But Severn Trent stressed the tap water would not yet be fit for drinking, even if boiled.
The Tewkesbury area would begin to get water over the next 24 hours, said a spokesman for Severn Trent.
The operation to provide emergency drinking water from bowsers and bottled water is to go on in the meantime.
Severn Trent said it would release details of areas that were due for reconnection on a daily basis.
Andy Smith, Severn Trent's director of water services, said: "Significant progress was made yesterday when an intensive testing and commissioning process made sure all damaged and flooded equipment was operational and fully repaired.
"However, this does not mean that customers will have water at their taps immediately. Ahead of water being reconnected, a Health and Safety advice notice is being issued.
"The most important message is that no one should drink the water when it starts coming back through the taps.
"The water must not be drunk, even after boiling. It must not be used for any food preparation, ice-making or even cleaning your teeth. It can however, be used for bathing, showering and flushing toilets.
Severn Trent Water said wide areas of Tewkesbury would begin to get water over the next 24 hours but for the majority of homes in Gloucester and Cheltenham, reconnection is still several days away.
A week ago some 130,000 homeowners in the area were warned they could be without fresh running water for a period of two weeks.
Tim Brain, Chief Constable of Gloucestershire Police, said: "The long-term weather forecast is of improving weather which does give all of the people of Gloucestershire something to look forward to next weekend.
"A water company has never had to recharge an entire system before. It takes over half the normal daily flow into the system to do this and it has to be done very carefully because we can't afford to get air locks into the system."