The new $2.5 million water treatment plant built beside the reservoir in Raetihi opened on Sunday to a crowd of hundreds of local people and Iwi.
Ruapehu District Council mayor Don Cameron said it was a great, great day.
"We were thrilled last year to be awarded a grant of $1.5m from Government to build the new treatment plant.
"Council added another $1m and we were able to get the project under way almost immediately.
"The new treatment plant will make a significant impact on the taste and odour issues in Raetihi,'' he said.