Garden Reach: A distribution pump at the Calcutta Municipal Corporation (CMC)'s Garden Reach water treatment plant burst open without warning on Saturday, letting out a gush that turned the room into a 20ft deep tank within minutes.

All three pumps and other equipment were shut down immediately and will take at least another 36 hours to restore, civic officials said.

Mayor Sovan Chatterjee called the disruption "unprecedented". Water supply to Behala, Maheshtala and some other localities was interrupted on Sunday, but the period of disruption was not as prolonged as had initially been feared.

A civic engineer said the pump whose iron shell gave way was being used to inject treated water from the plant into the distribution network. There are four such pumping stations at the Garden Reach plant, which supplies water to several neighbourhoods. The one that suffered damage used to supply water to areas like Behala, Maheshtala and Pujali, near Budge Budge.

The iron covering on top of the pump gave way around 9.15pm on Saturday. Within five minutes, nearly 20ft of water filled the room, an engineer said.

More than 30 pumps were used to suck out the water from the room by 5.30am on Sunday so that maintenance workers and engineers could enter and start repairs.

"Our engineers worked through the night and we were able to pump out the accumulated water from the room. We are hugely indebted to the four divers who went into the water and managed to close the valve," mayor Chatterjee said.

Sources in the CMC said the "divers" were employees of the CMC at the Garden Reach plant.

Mayor Chatterjee said his team had feared that there would be disruption in water supply to Behala and Garden Reach throughout Sunday, but that didn't happen because of alternative arrangements.

The mayor had reached the plant around 11pm on Saturday and was present there till all accumulated water had been flooded out by dawn. An engineer said water from the other three phases of the plant was pumped into the affected network to maintain supply.

The target is to resume normal supply by Tuesday. "We will dry the wires of the 6,000-volt motors and only then will we know if they work or need to be replaced," a CMC official said.

The Garden Reach plant produces 187 million gallon of treated water daily. This water goes to Jadavpur, Kasba, Behala, Tollygunge and Garia within the CMC area.