While the DJB describes its supplies as pure, the residents have often complained of its poor quality. (Rep photo: Getty Images)

From frantic scrambles at the back of tankers to brief windows of piped supplies -- that's how Delhi gets its drinking water.

But the residents of the world's second-most populous city don't really know how safe and clean their supplies are. The Arvind Kejriwal government says they are fit for drinking, but the Centre disagrees.

WATER TEST DRIVE

As the dispute over Delhi's water quality raged, India Today set out on a mission with a team of independent experts to test the precious liquid across the city and its neighbourhoods, the first of its kind by any media house in the country.

The team, with India Today's crews, crisscrossed Delhi's seven Lok Sabha constituencies plus Noida and Gurugram on the suburbs

METHODOLOGY

For three days starting December 9, they knocked on unfamiliar doors to sample drinking water in order to test it, on all WHO-prescribed parameters, in a world-class laboratory.

During India Today's test drive, the scientists explained their methodology in detail. The samples, they said, would be examined for physical, microbiological and chemical contamination. The samples, according to the scientists, would be tested for colour, odour, toxins, bacteria and other impurities.

Dr DK Chatterjee, one of the main independent experts accompanying India Today, cautioned that the ROs, a common feature in Delhi homes, can't be fully relied on for safe consumption.

"If the amount of total dissolved solids in drinking water, for instance, is less than 250 or over 500, then it's not fit for drinking. Maximum people in Delhi use RO purifiers. But what they do not realise is that these purifiers dilute TDS to 50, which makes the staple look clean but still unfit for drinking," Dr Chatterjee said.

Remember, the Delhi Jal Board (DJB) claims to be supplying 50 gallons per capita every day through a wide network of treatment plants, pumping stations and about 9,000 km of the distribution system.

The DJB describe its supplies as pure and wholesome filtered water to all of the capital city.

But residents have often complained of poor quality.

India Today's test drive has brought the facts out when quality has become a major election issue ahead of the February 8 vote.

POLITICAL WAR OVER WATER

On Nov 16, a political war over Delhi's water quality broke out after Union Minister Ram Vilas Paswan released a report by the Bureau of Indian Standards that found the supplies in the national capital most unsafe among 21 cities across the country.

In his rebuttal, Delhi Chief Minister Arvind Kejriwal slammed the BIS report and accused the Centre of playing "dirty politics". A DJB report later contradicted the BIS findings, saying water samples from eight out of nine places tested earlier are fit for drinking.

DOOR-TO-DOOR SAMPLING

As the confusion mounted, India Today with teams of independent experts went out in the quest for safe water. They made their first stop in the East Delhi constituency.

At a Mayur Vihar apartment, residents were found to be having serious issues with water quality.

"There is an acute shortage of water," complained Hriday, a resident of Mayur Vihar's Vasant Apartments. "Freshwater comes only in the morning and more often than not, it's dirty, muddy which can't be used."

Equipped with modern testing kits, the independent scientists accompanying India Today's journalists picked the samples from Hriday's home after sterilizing the tap per international protocols.

The same drill was conducted at random houses in South Delhi's Kalkaji neighbourhood, the New Delhi constituency's Vasant Vihar, Chandni Chowk's Civil Lines, North-East Delhi's Burari, West Delhi's Dwarka, and Noida and Gurugram on the outskirts.

LABORATORY FINDINGS

India Today's three-day mission revealed that the supplies were partly good, partly bad -- five out of nine areas passed the water-quality test and four failed it.

Here's the breakdown:

Laboratory reports from East, West, North-East Delhi and Gurugram rated the supplies unfit for drinking primarily because of bacterial contamination.

The test reports of Mayur Vihar, Dwarka, Burari and Gurugram read "with respect to bacteriological tests, water does not conform to IS: 10500-2012, and cannot be considered fit for drinking purpose".

But residents of New Delhi, South Delhi, Chandni Chowk, North-West and Noida constituencies need not worry as the lab tests found that the water flowing out of their home taps is safe for drinking. In their reports, the values were indicated in permissible limits.