More than 40,000 people in Shropshire were within minutes of losing their water supply after a power failure at a treatment works.
Power was restored as reserves were within 20 minutes of running out
Power was only restored as backup supplies were within 20 minutes of drying up for customers in Shrewsbury.
Severn Trent Water is urging people to conserve water while stocks are replenished overnight.
The water problem came as temperatures soared to a record equalling high in the West Midlands of 34.9C (94.82F).
The Met Office told BBC News that the temperature recorded at 1604 BST, equalled the record set in August 2003 for the hottest day in Birmingham.
Severn Trent's senior operations manager, Fraser Pithie, said the problem started at 1400 BST with the first power failure at the treatment works.
When backup electricity supplies also failed at 1600 BST, it meant 43,000 homes in Shrewsbury and western Shropshire were at risk of losing water.
"Power was restored as reserves were within 20 minutes of running out," he said.
"But we would still urge people to conserve water, particularly not to use sprinklers, so backup supplies can return to their normal levels."
The heat meant rail passengers faced a third day of delays across the region as speed restrictions were placed on trains after rail lines buckled in the soaring temperatures.
The heat forced two primary schools and a junior school to close in Birmingham.
Manor Park Primary School and Aston Tower Community Primary School in Aston were closed and infant and nursery classes at Jervoise Junior and Infant School have been cancelled for the remainder of the term.
Fire crews have attended scores of grass fires, while West Midlands Ambulance Service said it had received a record number of calls.
West Midlands Fire Service said it was receiving 1,000 calls, mainly for small grass fires, while Shropshire firefighters have warned about the dangers of dropping lit cigarettes and matches in the dry weather.
Smoking is set to be banned in car parks on Cannock Chase in Staffordshire from Friday to prevent possible fires.
Police in Worcestershire have warned about the dangers of swimming in the quarries in the Malvern Hills and drivers in the county are being told to watch out for melting tarmac.
In Staffordshire gritters have been sent out to cover some melting roads with granite dust to stop the surface sticking to car tyres.
Health workers have been warned that the heatwave could be dangerous for the very young or very old, or those with chronic health conditions.
Pollution levels are also expected to continue to be high in the Midlands, affecting those with lung conditions.
The hot weather has seen water consumption rocket in the region, although Severn Trent Water has said that there is no concern about reservoir levels, which are at about 80%.
However, it said consumption had risen by 200 million litres per day, the equivalent of 800,000 extra people.
Senior operations manager Fraser Pithie, said: "A sprinkler uses the same amount of water in just an hour as a family of four uses in a day."