Boris Johnson has vowed to look into bolstering flood defences after visiting the stricken area at lunchtime.
The Mayor of London also praised the emergency services' response to the major incident in Kenley where the water works have been flooded since Friday.
He hailed it as an "extraordinary operation" during his visit to Sutton and East Surrey Water's site.
Firefighters have been pumping out water around the clock to try and ensure no contaminated water gets into local water supplies.
The waterworks serves 46,000 homes, including in Caterham and Warlingham.
