About 31,000 properties have been left without water in St Leonards and parts of Hastings after a mains pipe burst.
Southern Water said it “worked through the night” to try to fix the problem, which has left homes in the East Sussex towns without supplies since Thursday afternoon.
The company said it could take the whole weekend to fix but that it was “working as quickly as is safe to do so” and making “good progress”.
Water is being delivered to vulnerable people and bottled water stations have been set up.
The three stations are at Asda and Tesco in St Leonards, and on Sea Road in Hastings.
However, Southern Water said it was trying to resolve “unforeseen issues” at the latter location on Saturday.
Labour MP candidate for Hastings & Rye, Helena Dollimore, said more than 50,000 people were in need of water as she urged the company to do more to resupply communities.
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Some schools and businesses, including the White Rock Theatre and Summerfields leisure centre, had to close on Friday due to the lack of water.
One person posted on X that her mother, who has mobility issues, had 12 bottles delivered but that six of them were stolen from her doorstep.
Another resident urged the water company to open a bottle station in the town centre “like we have been asking all day”.
A third local, posting on X, said: “Dear Southern Water – surely you have a responsibility to get water to people – not expect people to get to you.
“People without transport are unable to pick up in any quantity. Why not drop water at streets affected? Waiting in lengthy queues for water is not ok.”
Some have praised the firm’s response however, with one person on social media thanking it for the “brilliant service delivering to my disabled brother so promptly”.
Southern Water said: “We’re supplying more than 6,000 vulnerable customers who are on our priority service register in the affected area, and will investigate any issues where people who are on our list to receive water haven’t.”
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A fourth bottled water station had been scheduled to open on Saturday, but so far no details have been released.
A Southern Water spokesman said repairs had been been complicated by the location of the burst pipe.
It is in deep woodland near the A21, forcing the company to fell 50 trees to get access, Tim McMahon told BBC Radio 4.
“It is is by far the most difficult location I’ve ever seen,” he said.
