Aim: To assess the tap water hardness and it’s relation to urinary stone formation. Urinary stone disease or urolithiasis is one of the most common afflictions of modern society. It is a common urologic disease with prevalence of about 1%–20%, that is increasing throughout the world.Materials and methods: In a prospective study, from March 2017 to July 2018, biochemicalanalysis of urinary stones in patients was done. The drinking water supply ofpatients was evaluated and compared with biochemical stone analysis.Results: Stone analysis was performed in 150 patients. The most dominant composition ofurinary stones was calcium oxalate (74.7%), followed by uric acid (22%), ammonium urate (2%),andcystine (1.3%). Conclusion: we conclude thatthe dominant stone composition of inhabitants in and around Kanchipuram,where waterhardness is high, was calcium oxalate stones.