Businesses and houses within one square kilometre of Dalling Road, Hammersmith, were under water up to 8ft deep within minutes of the 30 in pipe being fractured during work to lay cable television and telephone lines.
Investigations are now under way to establish why preliminary test digs failed to locate the iron trunk mains, used to carry water from a nearby pumping station in central London. Its route was marked on service maps sent by Thames Water to McNicholas Construction, which is laying the cables for the Videotron Corporation.
Yesterday residents were demanding to know what had gone wrong. Amelia Bognar, who lives opposite the broken mains, said her Victorian terrace house had been irreparably damaged.
'You struggle for 30 years to make a home, and now everything is ruined. The water filled our basement study, it was 8ft deep. I have lost so many things of sentimental value, photographs and expensive books.'
Across Dalling Road, Annabel Lee had returned to her house after spending the night in an hotel. She had been stopped from going home by police on Wednesday evening when the flooding occurred.
'I have just spent pounds 3,000 on redecorating. Much of my antique furniture has been ruined. So are the carpets - the water was about a foot deep in my front room. God knows what damage it has done to the floorboards.'
In nearby Perrers Road, bookseller Ben Burdett was inspecting his girlfriend's J-reg Alfa Romeo Spyder convertible. Water stains could be seen halfway up the seat backs, and the car had refused to start.
Mr Burdett said he had tried in vain to keep the floods out of his home by wedging blankets against the front door.
'In the front room the water was above the skirting board. I lost hundreds of records which I won't be able to replace,' he said.
Alan Kelly, landlord of the Duke of York pub on Perrers Road, said he had lost several thousand pounds of stock stored in the basement.
'The fire brigade was here until 2am pumping out the water. The place stinks. We're closed for several days while we sort everything out.'
Colin McNicholas, director of McNicholas Construction, said it was 'extraordinary' that test digs to a depth of three feet had failed to disclose the mains 10in below the roadway. He said an inquiry into the incident was now under way.
'The explorations are carried out on the assumption that the mains is in a straight line. It may be that this mains turned.'
Mr McNicholas said that everyone affected would be compensated.