A day in any Delhi household begins with an act of trust: turning on the tap. Millions of people assume that the water flowing out is safe. Other than daily washing and cleaning needs, this water fills bottles for schoolchildren, goes into morning tea, and is used in the food we eat (water purifiers are still not as ubiquitous as most people think they are). But a seven-day sampling exercise conducted by Hindustan Times at 18 complaint-prone locations suggests this trust may not always be warranted. Laboratory analysis found that nearly 44% of the samples violated basic microbiological safety standards.
The sampling was conducted keeping two factors in mind: first, it targeted areas with long-standing complaints about water quality; and second, it aimed to establish a geographic representation of the city’s vast expanse, particularly its residential areas. Working with researchers from the Shri Ram Institute for Industrial Research, HT collected 18 water samples from locations across the city.
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{{/usCountry}}Laboratory analysis revealed that eight samples tested positive for total coliform or E. coli – indicators commonly associated with faecal contamination in drinking water.
All eight contaminated samples came from domestic tap connections. The problem appeared concentrated inside neighbourhood pipelines. West Delhi’s Rajouri Garden recorded the highest contamination levels, followed closely by Chilla village in east Delhi and DDA flats in Mayur Vihar Phase 3. In contrast, several pockets in south and central Delhi tested clean. The pattern suggests not a citywide collapse, but troubling, localised breakdowns within the distribution network. Strikingly, three of these domestic samples did not meet even the threshold for “bathing water”.
To be sure, none of the publicly accessible sources tested – a water vending machine at Connaught Place, a sweets shop in Kamla Nagar, a water cooler at Hindu Rao Hospital or a Delhi Jal Board (DJB) tanker in Chilla village – showed any microbial contamination.
The exercise was conducted in the wake of the Indore tragedy where, in the final week of December, a drinking water contamination outbreak in Bhagirathpura claimed 15 lives and left more than 250 people hospitalised after sewage infiltrated the local supply through a suspected pipeline leak. The incident, marked by widespread vomiting and diarrhoea, underscored how seemingly minor faults in urban water infrastructure can rapidly escalate into a public health emergency.
The warning signs in Delhi were always there. In several neighbourhoods across the capital, residents report receiving discoloured and foul-smelling water – yellow, grey, and even pitch-black – unfit for basic household use. Against the backdrop of Delhi’s expanding population and ageing pipeline network, concerns about possible sewage contamination have intensified.
While experts maintain that Delhi’s broader water distribution system remains largely dependable, the findings point to a deeper structural concern: an ageing and corroding network of sewer and water pipelines that may be allowing localised intermixing.
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The results raise pressing questions about infrastructure maintenance, monitoring mechanisms, and the urgent need to prevent isolated failures from developing into larger public health crises.
The methodology
HT looked at areas across the city where long-standing complaints of dirty water were shared with the DJB, or from where residents regularly voiced grievances on social media. Accompanied by two microbiologists from the Shri Ram Institute for Industrial Research (to ensure proper collection and that no contamination is introduced after the sampling), HT collected water samples from 18 such locations. The 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 5am and 7am, or during the evening supply window of 5pm to 8pm. Each sample was assessed for two key microbiological parameters: total coliform bacteria and Escherichia coli (E. coli).
Under Indian drinking water standards (IS 10500:2012), both total coliform and E. coli must be absent in 100 millilitres of potable water. In simple terms, the safe limit for both is zero.
Total coliform is a broader group of bacteria commonly found in soil, vegetation and the intestines of warm-blooded animals. Its presence signals that the water distribution system may be compromised or that contamination has occurred somewhere along the line. E. coli is a specific subset of coliform bacteria that originates in the intestines of humans and animals; its detection is a far more direct marker of faecal contamination. Tracking both is crucial: total coliform flags system vulnerability, while E. coli confirms that sewage contamination may have already occurred. Even low counts are unacceptable in drinking water because they indicate that disease-causing pathogens could also be present.
In addition to household taps, HT also tested water from DJB tankers and public water ATMs to compare supply points.
The 18 locations covered included Mayur Vihar Phase 3, Janakpuri, Rajouri 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 sweets shop in Kamla Nagar, a water cooler at Hindu Rao Hospital and two points in Chilla village in Mayur Vihar Phase 1 – one from a DJB tanker and one from the local pipeline supply.
Water from ATMs, tankers and institutional sources was found fit for drinking. But data showed total coliform in eight domestic samples – ranging from 6 colony-forming units (cfu) per 100 ml in East Vinod Nagar to as high as 920 cfu in Rajouri Garden.
E. coli was detected in six samples – from 4 cfu in Devli village to 270 cfu in Rajouri Garden.
Both parameters should have been zero.
The scale of contamination in some neighbourhoods was particularly stark. Rajouri Garden recorded 920 cfu/100 ml of total coliform and 270 cfu of E. coli. Chilla village’s domestic supply showed 870 cfu of coliform 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 bathing water in rivers, coliform levels should be below 500 cfu per 100 ml. At least three residential samples did not meet even this comparatively lenient “bathing water” threshold – let alone the zero-tolerance standard for drinking water.
“The results clearly indicate a problem in our system. Though it does not mean our entire water system is compromised, it most likely indicates that pipelines are corroding at places and sewer water is entering the water supply,” said Yamuna activist Pankaj Kumar, calling it a violation of the Jal Jeevan Mission’s commitment to safe tap water. While inadequate chlorination or treatment plant lapses are theoretical possibilities, he said, the pattern suggests localised pipeline breaches. He urged DJB to carry out targeted inspections wherever complaints arise.
Crumbling infrastructure in west Delhi
All three samples collected in problematic areas of west Delhi – Janakpuri, Rajouri Garden and Budhela village in Vikaspuri – showed contamination. Residents of Janakpuri’s A-1 block approached the National Green Tribunal last year and saw their pipeline network replaced after repeated complaints. DJB had admitted that some pipelines there were at least 40 years old.
A CPCB report in September had found “very high bacterial contamination”, with faecal coliform levels in some houses reaching 16 million units. In HT’s sampling, E. coli was not detected in the A-1 block, but total coliform measured 82 cfu – still a violation. The persistence of contamination despite a new 730-metre pipeline suggests that replacement in one stretch may not be sufficient if adjoining networks remain compromised.
Rajesh Mahajan, an RWA member, said his family stopped using tap water for drinking months ago.
“My father is over 70 and he falls sick because of the water. We use it only for washing clothes or cleaning. We get bottled water for cooking. The water is visibly brown and smells of sewage,” he said.
“I even paid for tests and conducted tests in 50 water samples from my area. DJB is not doing anything and when we complain, the water quality improves for a few days before worsening again,” he said.
In Rajouri Garden, where the highest readings were recorded, residents described a similar ordeal. Vijay Marwah, a businessman, said he now spends over ₹2,000 a week on tanker water for his three floors. “We have even collected the water and shown them how black it is, but nothing has changed. My children even refuse to use that water for bathing or brushing their teeth. We have entirely switched to a private tanker water,” he said.
At Budhela village, where total coliform was 24 and E. coli 6 cfu, residents said numbers do not capture the lived experience. “The water is smelly and dirty. Many families here fall sick,” said Surender Kumar, a driver. “Politicians come and make promises but they don’t fix anything. None of our relatives like to stay here. They said their water from wells is cleaner. We can’t afford tankers every day.”
East Delhi’s problems widespread
In Chilla village in Mayur Vihar Phase 1, residents largely depend on a daily DJB tanker that arrives around 7.30am. Though the colony has a formal pipeline, locals rarely use it. “The water is pitch black and filthy. I’ve not seen anyone using it,” said Satish, who runs a dairy. HT’s sample from the domestic tap recorded 870 cfu of total coliform and 230 cfu of E. coli. The tanker sample showed zero contamination.
Seven kilometres away in Mayur Vihar Phase 3’s DDA D2 Flats, total coliform was 620 cfu and E. coli 200 cfu. “The water stinks. Even when it looks clear, it carries with it a slight stench,” said RWA general secretary Vijay Singh Rawat, adding that complaints bring only temporary relief.
In East Vinod Nagar, total coliform measured 6 cfu. Residents said evening supplies are often worse. “I have been living here for over 30 years, and this has always been the case… Jaundice, diarrhoea – people here have faced all sorts of water-borne diseases,” said Lalit Goyal, 66, a construction contractor. “We spend around ₹100 daily on drinking water.”
South and southwest: Localised challenges
In Dwarka Sector 16B’s Janta Flats, total coliform reached 83 cfu and E. coli 20 cfu. “Water supply has always been an issue, but it appears to have worsened in the past two years. The water we get feels like it has oil mixed in it… We have shifted to bottled water,” said resident Sandeep Singh, who said pipe repairs did not resolve the issue.
Devli village in south Delhi lies at the heart of Sangam Vihar – notorious for its water problems. Here, total coliform was 16 cfu and E. coli 4 cfu. Residents say supply is erratic – often it comes every alternate day and very rarely arrives on consecutive dates. But even that water, residents said, is often discoloured. “There have been times when the direct water is black as if it’s coming straight from a drain. We never drink it. Most of us have water purifiers and those that don’t buy bottled water,” said 71-year-old Dayanand Piwal.
A decaying pipeline network
The eight contaminated locations serve as warning signals. Delhi’s water supply network spans over 15,400km, carrying treated water from nine treatment plants. Over 5,200km of pipelines are more than 30 years old, with another 2,700km between 20 and 30 years old. Ageing pipelines increase risks of leakage, negative pressure and cross-contamination where sewer lines run parallel.
Over the past decade, multiple colonies – from NCERT Colony, to recent cases in Janakpuri and Yojna Vihar – have reported instances of sewage mixing with tap water. Residents have increasingly approached courts for intervention.
Atul Goyal, president of United Residents Joint Action, said contamination often occurs during low-pressure hours. “When supply stops, negative pressure can draw in sewage through cracks or illegal punctures. Replacing old pipelines is urgent,” he said.
Meanwhile, concerns persist about testing capacity. Of DJB’s 25 water testing labs, only two – Haiderpur 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 issues. “Water and sewer lines often run close underground. When pressure drops, mixing can occur,” said Shashank Shekhar, assistant professor of geology at Delhi University.
Bhim Singh Rawat, a water sector expert and member of SANDRP, said Delhi needs an integrated water policy focused on infrastructure overhaul, reducing distribution losses and protecting water bodies. “Health of rivers, infrastructure and demand are interlinked. We need comprehensive reform, not piecemeal projects,” he said.
For now, the data does not suggest a citywide collapse. Ten of the 18 samples were clean. But the fact that nearly half violated zero-tolerance safety norms, and that the contamination was confined to domestic taps, should raise dangerous alarm bells for residents and officials alike.