About 10,000 homes in Tewkesbury have had their water restored using a temporary supply.
Water is being pumped from nearby Strensham, pic Mary Nelson
Severn Trent Water is issuing a strict "do not drink" warning for anyone connected to this supply - even when it has been boiled.
The firm said that while the water is clean, the pipes may have been under floodwater for several days so the firm cannot guarantee the quality.
The water is being diverted from the treatment works in Strensham.
It can be used for baths, showers and flushing toilets.
Severn Trent's operations manager, Fraser Pithie, said: "It is some progress and I totally agree that it is very, very small proportion.
"It's of no help whatsoever to people in Gloucester and Cheltenham and I don't want to overplay it. It's certainly helping the people in Tewkesbury."
A spokesman said the re-routing was an "imaginative solution" and added: "We are using a route we don't normally use. It hasn't been attempted before as it is very complex."
Mayor Phil Awford said the Germany-based humanitarian association Aviation Sans Frontieres had offered the borough 80,000 litres of bottled water, which should arrive on Friday.
"This offer of assistance came as a surprise, but a most welcome surprise," he added.
Across Gloucestershire, 350,000 people were cut off when the Mythe waterworks was flooded. It may be not be fully operational again for another two weeks.
Andy Smith, from Severn Trent Water, said to anyone reconnected in the town: "Water reaching your taps should not be used for drinking, food preparation, ice-making or cleaning your teeth.
"I need to be very clear about the instructions: if your water supply has gone off already, or is lost shortly, you should not drink the tap water when it comes back on, even after boiling."
Homeowners are being asked to make sure taps are turned off to help fill the network faster.
Severn Trent Water said the water may be intermittent and discoloured.
A further five million litres of bottled water was being handed out across the county on Thursday.
And up to 900 bowsers are in place, but are emptying quickly.
Mr Awford has also launched an appeal for the benefit of those residents affected by the flooding.
"I have already received a number of kind offers of help for those caught up in this extreme flooding.
"I therefore asked that an appeal fund be set up to recognise the generosity of both local communities and individuals, and also from individuals and communities from much farther afield."