Tallinna Vesi AS Tallinna Vesi (Tallinn Water) is an Estonian company which offers water supply, wastewater collection and treatment services. is the largest water utility company in Estonia. The company is serving over 460,000 people in Tallinn Tallinn, the largest city and capital of Estonia (population 440 000). and Harju County County in northern Estonia(pop. 620,000). . The company was established in 1967.