Ten thousand homes were without water on Sunday after a mains pipe burst in north London.
Thames Water said the supply was restored to the majority of homes by 1930 BST after the pipe burst at Staples Corner at 0500 BST.
Bottled water was handed out to the elderly and disabled in the Finchley Road, Hendon and Golders Green areas.
The M1 was closed due to flooding and fully reopened at about 1300 BST. Work is continuing to repair the pipe.
A Thames Water spokesman said engineers had managed to draw in water from elsewhere.
He apologised for the inconvenience to customers and said that engineers were carrying out repairs.
Lane restrictions on the A406 are expected to stay in place for up to two days.