The Brihanmumbai Municipal Corporation on Sunday asked citizens to boil water before drinking as heavy rains over the last two days had led to flooding in the water purification complex at Bhandup.
The flooding has affected electrical equipment that control the pumping and filtration processes there, one of the major sites of water supply to the country's financial capital, he said.
While the pumping mechanism would be restored in a few hours, much more time will be taken to get the filtration process up and running, the official said, adding that boiling water before drinking was the best precaution at the moment.
The inundation at the complex has affected water supply in most parts of the metropolis, the official added.
As Mumbai slept the skies opened up with thunder, lightning and heavy rains measuring between 197 mm to over 235 mm in some areas in barely 3-4 hours, as per the IMD Mumbai, which submerged many areas and hit road and rail traffic badly.
The BMC's gauges recorded rainfall of 177 mm in South Mumbai, 205 mm in Eastern Suburbs and 195 mm in Western Suburbs.
In many areas, people reported waist-deep waters with the flood waters entering the ground floor homes or shops in the vulnerable or low-lying areas.
The rains hit the suburban train services with WR lines flooding at Nalla Sopara and Virar, and the CR tracks getting submerged at Dadar, Sion, Kurla, Parel, Chunabhatti and Tilaknagar.
With flood waters entering the Bhandup Water Treatment Plant, the BMC has said that there will be water shortages in some parts of the city till repairs are completed and urged people to use water sparingly.
The IMD Mumbai has warned of more rains during the day, including a few very heavy spells for which the BMC, NDRF, Police, Fire Brigade and other agencies are on high alert in Mumbai and the entire coastal Konkan region.