Question

Read the following passage carefully and answer the question that follows. In most Indian cities, a silent crisis flows through ageing water pipelines: leakage. Municipal engineers estimate that in some networks nearly a third of treated water never reaches a tap; it seeps away through corroded joints, cracked pipes and fittings loosened by years of pressure fluctuation. Every litre lost is not merely water wasted; it is energy squandered in pumping, chemicals spent in treatment, and revenue foregone by the utility. The remedy is often unglamorous. A plumber who replaces a worn washer, tightens a gland nut to the correct torque, or reseats a leaking valve can save thousands of litres a year. Yet the work demands more than strong hands: it requires reading a pressure gauge correctly, choosing the right spanner so as not to round off a brass nut, and knowing when a joint needs thread sealant rather than brute force. As cities grow thirstier, the humble craft of keeping water inside the pipe has become a frontline defence against scarcity. What is the central idea of the passage?