Water Supply and Drainage (VIO) is the supplier of water services in public water supply and sewage on the territory of the City of Zagreb and wider Zagreb area. VIO supplies water to the inhabitants of Zagreb, Samobor, Sveta Nedjelja and Stupnik municipality, companies Dukom d.o.o. – Dugo Selo, Zelinske komunalije d.o.o. – Sv. Ivan Zelina and Komunalac d.o.o. – Vrbovec, also performing services of wastewater sewage for the inhabitants of Zagreb and Sveta Nedjelja. VIO has certified laboratories that perform testing of the supplied water safety for human consumption and testing the quality of own wastewater. The official laboratories for control and monitoring the water for human consumption are in Hrvatski zavod za javno zdravstvo (Croatian Institute for public Health) and Zavod za javno zdravstvo (Intitute for Public health) Dr. Andrija Štampar.