The systems, totalling about 40km, comprise nine identical networks in Christchurch, a residential and commercial network in Tekapo, two residential networks in Queenstown and a commercial network in Te Anau.
Eight are now transporting LPG, and the others will go live over the next year as residential subdivisions are completed.
The purchase follows On gas' acquisition of TMU's commercial network in Wanaka last July.
NGC chief executive Bryan Crawford said reticulation systems were being increasingly used to transport LPG as demand for this product expanded, particularly in the South Island.
"We continue to experience growth in our LPG cylinder business, but where there are concentrations of LPG customers it can be more effectively distributed through pipelines," he said.
The acquisition was consistent with NGC's strategic focus on energy infrastructure development and On gas aimed to further develop these networks and to seek opportunities for developing new networks throughout the country.
