Four fire engines and around 25 firefighters were called to a flooding on Brookside Close in Harrow.
A range of bungalows covering an area of around 200 square metres were flooded to a depth of approximately 50 millimetres after a water main burst. One woman was treated on scene by London Ambulance Service crews and was taken to hospital.
The Brigade was called at 0702 and the incident was over for firefighters by 1014. Fire crews from Stanmore and Wembley fire stations attended the scene.