Drinking water will be in short supply for about 72 hours in the worst-hit areas of Gloucester, Cheltenham and Tewkesbury.
The pumping plant at Mythe near Tewkesbury was put out of action by the scale of the flooding.
Emergency crews have also been trying to stop an electricity substation which feeds 500,000 Gloucestershire homes from shutting down.
Instances of panic buying of drinking water have also been reported.
The RAF said the scale of its operation to remove stranded people from their homes was the biggest it had ever undertaken in peacetime.
In an attempt to bolster drinking water supplies, about 600 water tanks have been drafted in with military help while 150,000 homes in Gloucestershire are now without fresh water.
The Rivers Severn and Avon which join in Tewkesbury have burst their banks and flooded much of the town and surrounding area.
Warning signs ignored
Meanwhile, West Mercia police said their rescue operations were being hampered in some cases by flood sight-seers. A number of abandoned cars had also been broken into by thieves.
A spokesman said: "Not only are drivers stopping on the roadside to look at and photograph flood scenes, but some are driving past clear flood warning signs."
The station has been evacuated and equipment shut-off
He said they were "endangering themselves and their passengers, and possibly causing more work for over-stretched emergency services".
Car owners are being urged to collect their vehicles as soon as possible to avoid opportunist thieves.
At Stroud Hospital doctors have accepted 11 patients from Tewkesbury Hospital.
RNLI crews were in the town centre checking properties for stranded people.
Alan Head, of the RNLI, said his team in Tewkesbury had rescued about 20 people who were caught out by the rising waters.
Gloucester has been put on a severe flood warning with water just 30cm (1ft) short of flood defences.
Nearly 500 people in the dockside area of Gloucester are preparing to leave their homes in preparation for the Severn bursting its banks.
No deaths reported
Water levels in the city are equal to the 1947 flood, according to many experts.
Police confirmed that HMP Gloucester which is situated near the docks, would not be evacuated in the event of flooding.
Chief Constable Dr Tim Brain said many of the county's roads had re-opened and there had been no reports of deaths or missing persons associated with the floods.
Terry Standing, chief fire officer for Gloucestershire Fire and Rescue Service, said they were poised for breach of the River Severn in Gloucester Quays but river water levels had stopped rising.
More flood water is expected to arrive in Tewkesbury
Severe flood warnings are in force for the Rivers Severn and Avon.
Severn Trent Water said the water supply situation was serious and urged customers to conserve water, not run baths or to hose down any dirty areas on Sunday.
Shona Arora, director of Public Health for Gloucestershire, advised anyone affected to conserve water and not to panic buy.
She advised people not to take baths and not to clean up flood damage as that would use up water supply from the mains system.
The Severn Trent spokesman said: "The situation is serious, our pumping and treatment works at Mythe has been flooded by the water.
"It has been overwhelmed. We cannot remember a time the works itself have ever been flooded like this. It doesn't sit on the flood plain but is some way off."
Four lorry loads of bottled water for emergency distribution were sent to Sainsbury's in Barnett Way, Barnwood, Gloucester and Tesco in Quedgeley.
But each person is being restricted to two bottles although tankers containing fresh water were on their way to ease the situation.
"Yorkshire Water, Anglia Water and Thames Water have all offered their services to help Severn Trent and the Army may be used to distribute the water to areas most in need," the spokesman added.
Rail operator First Great Western said it had managed to run a "reduced and disrupted" service although passengers had been warned to expect cancellations and extended journey times.
Gloucestershire County Council is trying to find suppliers of portable loos to help those without access to toilets.
BBC Radio Gloucestershire is running special programming with regular updates on the flooding.
It can be heard on 1413 MW, 104.7, 95.0, 95.8 FM, and online bbc.co.uk/gloucestershire