The emergency services have been at a Gloucestershire substation throughout the night to prevent flood waters from forcing it to shut down.
Emergency services say the situation is under control
By 0400 BST police had described the situation at Walham as "under control" after the Environment Agency said river levels in the area had peaked.
Power has also been restored to homes affected by the flooding at the Castlemeads substation.
But in Gloucestershire 350,000 people are still without fresh water.
The National Grid said it would be able to re-route some power if Walham were to succumb.
Duncan Jordan, of Gloucestershire County Council, admitted the situation was "grim", but said he was "cautiously optimisitic" that the pumps would continue to keep the worst of the water out.
National Grid spokeswoman Sarah Harris said: "We've worked extremely closely with the armed forces, fire brigade, to try to stop the water from penetrating our site.
"What we've done is build a one kilometre wall around the site to stop the water flowing through and as things stand at the moment that wall seems to be sufficient and the situation is being maintained."
The Mythe water treatment works is still out of action and the prognosis is not good
Chief Constable Tim Brain
The Chief Constable of Gloucestershire Police, Tim Brain, said the situation was an "ongoing emergency".
The likely fate of the Walham substation was discussed at the government's emergency planning committee on Monday night.
Power cuts have also taken one of the county's main sewage treatment centres off-line.
The Netheridge treatment centre stopped working when its electricity supply was interrupted.
Generators are on site and Severn Trent is stressing there is good capacity to store waste water at the site.
Mr Brain said the worst could still be on its way with regard to supplies of fresh water.
"With respect to the Mythe water treatment works, that is still out of action and there I am afraid to say the prognosis is not good," he said.
"The best case scenario is seven days and we have been told up to 14 days before it can become fully operative."
Police said the emergency services are unlikely to be able to get into the works before Wednesday.
Gloucester is braced for more flooding
Gloucester, Cheltenham and Tewkesbury have been worst affected by a lack of drinking water.
Bottled water, water tanks and water containers have been brought in to bolster supplies, with supermarkets reporting some instances of panic buying for basic supplies.
Mr Brain added: "I must emphasise that the situation we face remains unprecedented.
"There are still high levels of water and there is still more water to come down the Severn and other tributary rivers and we have by no means passed the peak of the ongoing emergency. We are not yet in a full recovery stage."
The areas hit hardest by flooding in addition to Gloucestershire and Worcestershire, have been Warwickshire, Herefordshire, Lincolnshire, Oxfordshire and Berkshire.
Residents at risk of flooding in Oxford have been told they must expect to leave their homes if water levels on the Thames continue to rise.
The Environment Agency still has seven severe flood warnings in place - three on the Severn, two on the Thames, and one each on the Great Ouse in Bedfordshire and the Ock in Oxfordshire.