According to official sources, Puducherry is currently dependent on over 100 deep tube-wells in the urban and peripheral areas for the city’s day-to-day water needs. As many as 220 million litres of water are supplied through pipelines to overhead reservoirs located in the urban limits. With water being extracted for over 16 to 20 hours per day to meet the rising demand, the quality of water has started deteriorating over a period. As a result, various parameters such as Total Dissolved Solids (TDS), pH, nitrate, iron, and chloride have increased over the permissible levels.

(Source)