People living in Fiveways in Brighton were unable to drink, wash or flush the toilet after the leak in Preston Drove.
Southern Water fixed the leak by lunchtime.
A statement said: “We’re pleased to say repairs to the burst 6in main in Preston Drove, Brighton, are now completed and customers should start to see supplies slowly return over the next couple of hours.
“It will take some time to refill the network as we balance the pressure to ensure no further problems occur.
“Customers affected by the burst may see some discolouration when their supply returns but, although this doesn’t look nice, it is not harmful and will usually clear in 24-48 hours.
“We’d like to thank all our affected customers for their patience and understanding while we worked on this emergency repair.”
Patricia Franklin, 71, who lives in Cleveland Road, said: “Water is just pouring down the road.”
She said she had not heard anything from the water board.
“In this heat it’s a bit naughty just to leave us with no notification,” she added.
And she raised concerns about vulnerable elderly people on what is tipped to be the hottest day of the year.
“They go to turn their taps on and there’s no water,” she said.
One resident posted on Twitter: “No water in parts of Fiveways area in Brighton.
“Burst water main on Preston Drove, water flowing down Edburton Ave.
“Southern Water people are there. Hope it’s sorted soon.”
Southern Water said earlier on Twitter: “We’re dealing with a burst main in Preston Drove, Brighton which has led to some customers in the area experiencing water loss.
“Our specialist crews arrived on site but unfortunately parked cars obstructed our work. The police have moved the cars & we’ve begun the repair.”
And they said: “We understand how difficult it can be to be without water, especially during hot weather, and we would like to thank our affected customers for their patience while we carry out this emeregncy work.”
Hannah James, owner of The Pet Shed in Preston Drove, said: “We heard the repairs will take a while so we welcome anyone to come in to fill up their water bottles.
“Today is a very hot day so we expect people to come in. Our taps are still running, but not quite as fast as it should be.
“There are a lot of big vehicles outside doing repairs and resurfacing the road, it’s going to be a very busy day.
“Hope the water pipe will be fixed soon so everything can go back to normal.
“We just want to do something for the community.”
Southern Water added: “The burst in Preston Drove, Brighton, is on a 6in main, which has affected around 1,365 properties with either low pressure or no water.
“We are currently digging down to expose the pipe to find out the scale of the problem, which will also tell us what needs to be done to repair it and also provide us with an idea of timescales.
“We are investigating the best way to restore supplies in the meantime, whether it’s through a rezone or by providing alternative water supplies.
The start of the repair was hampered by several parked cars which the water company was unable to move without the help of the police.
Southern Water said: “Pipes can leak and burst for a number of reasons, including age, extreme temperatures, damage, increased water pressure and misuse.
“Extreme heat leads to dry soil, which is much looser than moist soil, so pipes have more room to shift and move around.
“This can lead to pipes breaking as they shift and move more than usual.”