The upgrade also included installation of a new six million-litre reservoir that doubles the plant's capacity and provides the town with at least 24 hours of water storage,
constructing a new chemical dosing system, installing an ultra violet water treatment system, constructing a new chlorine shed, and additional electrical and telemetry works.
Horowhenua District Council's projects managererry O'Neill said a secure and reliable water supply is essential to the wellbeing, health and safety of people and communities in Levin.
"This project was completed within budget, on time and demonstrates that Horowhenua District can have first-class infrastructure at a cost our community can afford, by ensuring we are focused on the right outcomes," he said.
Council has a resource consent until July 2042 allowing it to extract up to 15,000 cubic metres of water per day from the Ohau River.
The district council operates five drinking water supply schemes of which Levinis the largest, currently supplying approximately 20,000 people. It was the last to be upgraded, following Tokomaru, Shannon, Foxton and Foxton Beach.