New Delhi, Jan. 5 -- Of the 15,600km water supply network in the Capital, nearly 18% is more than three decades old and in need of replacement, says a Delhi Jal Board (DJB) report. Ageing pipes are prone to cracks and leaks that can raise the likelihood of water contamination. Concerns over water supplies in cities are in focus after contaminated water in Indore (Madhya Pradesh) killed 10 people. "There is 2,800km (17.94%) of network which is more than 30 years old," the report, accessed by HT, said. It further noted that at least half of the water (50-52%) is non-revenue water (NRW), unaccounted for due to non-metered connections, punctured pipes, thefts and leakages. NRW can cause significant financial and resource loss for utilities. DJB plans to undertake a study of the entire supply network through Japan International Cooperation Agency (JICA) or similar technical experts to revamp the supply network, the report states. This has significant implications for Delhi. The DJB currently operates nine water treatment plants across the city that supply around 1,000 million gallons water per day (MGD). According to DJB's water quality surveillance reports from December 22 and 26, of the 7,129 samples of drinking water from various parts of city, samples from 100 locations were found "unsatisfactory". Some were taken from underground reservoirs and booster pump stations. The localities where samples failed included DDA flats in Mansarovar Park, Puran Nagar Palam, several samples in Sector 13 Dwarka, Bhagat Enclave in Uttam Nagar, booster station at Siraspur, Gali 8 Mohammadpur, Uttam Nagar's Vijay Vihar and Kiran Garden, and Vijay Colony in Burari, among other places. DJB officials claimed that corrective action was taken after samples failed. The water utility relies on testing residual chlorine levels in the supply water samples to test their suitability, officials said. Speaking to HT, RWAs in south, central, old, and north Delhi said water contamination from sewage and drainage-related issues remain an everyday reality for them, despite multiple complaints to authorities. "The water supply lines run next to sewage lines. Moreover, people use motor pumps during the supply hours. Broken old pipes and widespread use of pumps makes the initial 10-15 minutes of supply water smelly and contaminated," Ashok Bhasin, president of the North Delhi RWA said, adding, "Supply lines in areas like Old Delhi, Ghantaghar, Sabzi Mandi, Malkaganj, and Chandrawal are around 40-50 years old." In response, a senior DJB official said that a large-scale replacement programme of water supply lines is being undertaken in areas such as Yojana Vihar, Jagriti Enclave, Shanti Mohalla, Jhilmil Industrial Area, Dilshad Garden, Gandhi Nagar, and IP Extension. "The government has also cleared Chandrawal catchment area improvement project under which 1,000km of new water pipelines will be laid, reducing leakages and contamination," the official added. Over the last one year, the Delhi High Court and NGT have pulled up the DJB on several instances of drinking water supply contaminated by sewage. Last year, after residents of A block in Janakpuri complained of muddy water supply in their area, the Central Pollution Control Board (CPCB) in September found "very high bacterial contamination", with faecal coliform levels in some houses reaching 16 million units - a parameter that should be zero in potable water. The NGT had criticised DJB for failing to act on it, following which the process to replace supply line started. Activists also flagged loopholes in the water testing mechanism of DJB. Of its 25 water testing labs in the city, only two - Haiderpur and Wazirabad - appear on the accreditation list of National Accreditation Board for Testing and Calibration Laboratories (NABL), Yamuna activist Pankaj Singh has alleged. Atul Goel, the president of URJA, an umbrella organisation of around 2,500 RWAs, said that the concern is more prominent in areas like Karol Bagh, Rajinder Nagar, Chandni Chowk, Model Town and Shakti Nagar. "Initial water supply is almost always contaminated...There is an urgent need to replace old pipelines and plug sites where people have illegally punctured them," he added....