The day begins in any Delhi home with an act of trust: turning on the tap. Millions of people assume that flowing water is safe. Beyond daily washing and cleaning needs, this water fills school children’s bottles, goes into their morning tea, and is used in the food we eat (water purifiers are still not as ubiquitous as most people think). But the Hindustan Times’ seven-day sampling of 18 complaint-prone locations suggests such confidence may not always be justified. Laboratory analysis found that approximately 44% of samples violated basic microbiological safety standards.
Sampling was conducted taking two factors into account: first, it targeted areas with long-standing complaints about water quality; Secondly, it aimed to create a geographical representation of the vast area of the city, especially its residential areas. Working with researchers from the Shri Ram Institute of Industrial Research, HT collected 18 water samples from locations across the city.
Laboratory analysis revealed that eight samples tested positive for total coliform bacteria or E. coli, indicators usually associated with fecal contamination in drinking water.
All eight contaminated samples came from local tap connections. The problem appeared to be concentrated within adjacent pipelines. Rajouri Park in west Delhi recorded the highest pollution levels, closely followed by Chilla Village in east Delhi and DDA apartments in Mayur Vihar Phase 3. In contrast, several pockets in south and central Delhi were tested clean. This pattern does not point to a city-wide collapse, but rather to worrying local collapses within the distribution network. Surprisingly, three of these local samples did not even meet the “bathwater” threshold.
Certainly none of the publicly available sources tested – the water vending machine in Connaught Place, the sweet shop in Kamla Nagar, the water cooler at Hindu Rao Hospital, or the Delhi Jal Board tanker in Chilla Village – showed any microbial contamination.
The exercise was conducted in the wake of the Indore tragedy where an outbreak of drinking water contamination in Bhagirathpura, in the last week of December, killed 15 people and hospitalized over 250 people after sewage leaked into local supplies through a suspected pipeline leak. The incident, which was characterized by widespread vomiting and diarrhea, highlighted how simple deficiencies in urban water infrastructure can quickly escalate into a public health emergency.
The warning signs in Delhi have always been there. In many neighborhoods in the capital, residents report receiving discolored and foul-smelling water – yellow, gray and even black – unfit for basic domestic use. Against the backdrop of Delhi’s growing population and aging pipeline network, concerns have been growing about possible sewage contamination.
While experts stress that Delhi’s broader water distribution system remains largely reliable, the findings point to a deeper structural concern: an aging and corroded sewer and water pipeline network that may allow local mixing.
The findings raise pressing questions about infrastructure maintenance, monitoring mechanisms, and the urgent need to prevent isolated failures from developing into larger public health crises.
HT looked at areas across the city where long-standing complaints about dirty water were shared with the DJB, or where residents regularly voiced their complaints on social media. Accompanied by two microbiologists from Shri Ram Institute of Industrial Research (to ensure proper collection and no contamination after sampling), HT collected water samples from 18 such sites. Water was taken directly from supply taps to avoid contamination from overhead tanks or household storage containers. Samples were collected only during active supply hours, typically between 5 a.m. and 7 a.m., or during the evening supply window of 5 p.m. to 8 p.m. Each sample was evaluated in terms of two main microbiological parameters: total coliform bacteria and Escherichia coli (E. coli).
Under Indian Drinking Water Standards (IS 10500:2012), both total coliforms and E. coli should be absent in 100 milliliters of drinking water. In simple terms, the safe limit for both is zero.
Total coliforms are a broad group of bacteria that are commonly found in soil, plants, and the intestines of warm-blooded animals. Their presence indicates that the water distribution system may be compromised or that contamination has occurred somewhere along the line. Escherichia coli is a specific subset of coliform bacteria that originates in the intestines of humans and animals. Its detection is a more direct sign of fecal contamination. Tracking both is crucial: Total coliforms indicate a system is weak, while E. coli confirms that sewage contamination may have already occurred. Even low numbers are unacceptable in drinking water because they indicate the possible presence of disease-causing pathogens.
In addition to household taps, HT also tested water from DJB tankers and public water ATMs to compare supply points.
The 18 locations covered include Mayur Vihar Phase 3, Janakpuri, Rajuri Garden, Batla House, Budhela Village (Vikaspuri), Madanpur Khadar, Maharani Bagh, Mandawali, East Vinod Nagar, Devli Village in Sangam Vihar, Vasant Kunj, Dwarka Sector 16B, Rohini Sector 17, and a public drinking water ATM at Connaught Place. Samples were also collected from a sweet shop in Kamla Nagar, a water cooler at Hindu Rao Hospital and two points at Chilla village in Mayur Vihar Phase-I – one from a DJB tanker and one from a local supply pipeline.
Water from ATMs, tanks and institutional sources was found to be safe to drink. But the data showed total coliforms in eight local samples – ranging from 6 colony-forming units (cfu) per 100 ml in East Vinod Nagar to as high as 920 cfu in Rajouri Park.
E. coli was detected in six samples – from 4 CFU in Divli village to 270 CFU in Rajouri Park.
Both parameters must be zero.
The extent of pollution in some neighborhoods was particularly stark. Rajouri Garden recorded 920 CFU/100 ml of total coliforms and 270 CFU of E. coli. The local supply in Sheila Village showed 870 CFU of coliforms and 230 CFU of E. coli. Mayur Vihar Phase 3 reported 620 CFU and 200 CFU respectively.
For perspective, the Central Pollution Control Board (CPCB) states that for river bathing water, coliform levels should be less than 500 colony-forming units per 100 ml. At least three residential samples did not meet even the relatively lenient “bathwater” threshold – let alone the zero-tolerance standard for drinking water.
“The findings clearly indicate that there is a problem in our system. Although this does not mean that our entire water system is at risk, it more likely indicates that the pipelines are corroding in some places and sewage is entering the water supply,” Yamuna activist Pankaj Kumar said, calling it a violation of the Jal Jeevan Mission’s commitment to safe tap water. While insufficient chlorination or lapses at treatment plants are theoretical possibilities, the pattern points to local breaches in pipelines, he said. He urged the DJB to conduct targeted inspections wherever complaints arise.
Dilapidated infrastructure in West Delhi
The three samples collected in problem areas in west Delhi – Janakpuri, Rajouri Garden and Bodela village in Vikaspuri – showed contamination. Residents of Block A-1 in Janakpuri approached the National Green Tribunal last year and saw their pipeline network replaced after repeated complaints. DJB has admitted that some of the pipelines there are at least 40 years old.
A CPCB report in September found “very high bacterial contamination,” with M Fecal coliform levels in some homes reach 16 million units. In the HT sample, no E. coli was detected in cluster A-1, but the coliforms totaled 82 cfu—still a violation. The persistence of contamination despite the laying of a new 730-metre pipeline suggests that replacement in one stretch may not be sufficient if adjacent networks remain vulnerable.
RWA member Rajesh Mahajan said his family stopped using tap water for drinking months ago.
“My father is over 70 years old and gets sick from the water,” he said. “We only use it to wash clothes or clean. We get bottled water for cooking. The water is clearly brown and smells like sewage.”
“I even paid for the tests and conducted tests on 50 water samples from my area. DJB does not do anything and when we complain, the water quality improves for a few days before it deteriorates again,” he said.
In Rajouri Park, where the highest readings were recorded, residents described a similar ordeal. Vijay Marwa, a businessman, said he is now spending too much $2000 per week on a water tank for its three floors. He added: “We collected water and showed them how black it was, but nothing changed. My children even refuse to use that water to shower or brush their teeth. We have completely switched to using a private water tank.”
In the village of Budela, where the total number of coliforms was 24 and E. coli was 6 endemic units, residents said the numbers did not reflect life experience. “The water is smelly and dirty. Many families here are falling ill,” said Surinder Kumar, a driver. “Politicians come and make promises but they don’t fix anything. None of our relatives like to stay here. They said the well water they get is cleaner. We can’t afford tankers every day.”
East Delhi’s problems are widespread
In Chilla village in Mayur Vihar, Phase-I, residents largely depend on the daily DJB tanker that arrives around 7.30 am. Although the colony has an official pipeline, locals rarely use it. “The water is black and dirty,” said Satish, who runs a dairy factory. “I didn’t see anyone using it.” The HT sample from the household tap recorded 870 CFU of total coliforms and 230 CFU of E. coli. The tanker sample showed no contamination.
Seven kilometers away at DDA D2 apartments in Mayur Vihar Phase 3, total coliforms were 620 cfu and E. coli 200 cfu. “The water smells bad. Even when it looks clear, it has a slight bad smell,” said Vijay Singh Rawat, general secretary of the Water Workers’ Association, adding that complaints only bring temporary relief.
In East Vinod Nagar, total coliforms reached 6 endemic units. Residents said evening supplies were often worse. “I have been living here for more than 30 years, and this has always been the case… jaundice, diarrhea – people here have faced all kinds of water-borne diseases,” said Lalit Goyal, 66, a building contractor. “We spend around $100 per day on drinking water.
South and Southwest: Local Challenges
At Janta Flats in Dwarka Sector 16B, the total number of coliforms reached 83 colony units and E. coli 20 colony units. “Water supply has always been a problem, but it seems to have worsened in the last two years. The water we get looks like it has oil mixed in… We have switched to bottled water,” said Sandeep Singh, a resident, who said fixing the pipes had not solved the problem.
Divli village in south Delhi is located in the heart of Sangam Vihar – famous for its water problems. Here, the total coliforms were 16 cfu and E. coli were 4 cfu. Residents say supplies are irregular, often coming every alternate day, and rarely arriving on consecutive dates. But even that water, residents say, often changes color. “There were times when the direct water was black as if it was coming straight from the drain,” said 71-year-old Dayanand Bewal. “We never drink it. Most of us have water purifiers and those who don’t buy bottled water.”
Degraded pipeline network
The eight contaminated sites serve as warning signs. Delhi’s water supply network extends over 15,400 km, carrying treated water from nine treatment plants. More than 5,200 km of pipelines are more than 30 years old, with another 2,700 km aged between 20 and 30 years. Old pipelines increase the risk of leaks, negative pressure, and cross-contamination as sewer lines run in parallel.
Over the past decade, multiple colonies — from the NCERT colony, to the recent cases in Janakpuri and Yojna Vihar — have reported cases of sewage mixing with tap water. Residents are increasingly turning to the courts for intervention.
Atul Goyal, president of United Residence Joint Action at nts, said pollution mostly occurs during low-pressure hours. “When the supply stops, negative pressure can draw sewage through cracks or illegal holes. Replacement of old pipelines is urgent,” he said.
Meanwhile, concerns remain about testing capacity. Of DJB’s 25 water testing laboratories, only two – Hyderpur and Wazirabad – are NABL accredited. Routine monitoring often focuses on residual chlorine rather than comprehensive microbiological testing.
The way forward
Experts said the contamination levels detected indicate systemic vulnerability rather than isolated household plumbing problems. “Water and sewer lines are often close to underground,” said Shashank Shekhar, assistant professor of geology at Delhi University. “When the pressure drops, mixing can occur.”
Bhim Singh Rawat, a water sector expert and member of SANDRP, said Delhi needs an integrated water policy that focuses on repairing infrastructure, reducing distribution losses and protecting water bodies. “River health, infrastructure and demand are interconnected,” he said. “We need comprehensive reform, not piecemeal projects.”
At this time, the data does not indicate a city-wide collapse. Ten of the 18 samples were clean. But the fact that nearly half of these cities violated zero-tolerance safety standards, and that the contamination was limited to household taps, should ring serious alarm bells for residents and officials alike.
