Wellington will be on summer water restrictions from Sunday with the level one limits meaning sprinklers and irrigation systems can only be used on alternating days and only at certain times.
Moving to restrictions as daylight savings kicks in is a decision Wellington Water has made consistently over the past few years.
But chief advisor Laurence Edwards said water demand had been trending above what had been seen in previous years since May.
While population growth was a contributing factor, it was mostly due to "an ageing network and increasing leaks", he said.
The leaks had been on both the public side of the network and private property.
Private property, Edwards estimated, had contributed around 40 percent of the water lost.
Wellington Water had been working to remedy the situation.
Edwards said staff were "implementing a more intensive, urgent programme of work" to identify and fix leaks on both the public network and within private properties, and reduce the run time of the most significant leaks.
Staff were also looking at other measures they could take across the network and would be recommending further work to each of the entity's client councils, he said.
Residents were being asked to follow the restrictions and be mindful of outdoor water use.