The NSW government and Hunter Water will re-open the reservoir on Tyrrell Street, The Hill to the public in 2015, almost 50 years after it was drained and closed.

Built in 1882, the reservoir is one of the oldest in Australia. At the time, Newcastle was booming and a reliable water supply was needed to store water so it could be delivered straight to people's homes.

Water was pumped into the reservoir from the Walka Water Works near Maitland.

The underground reservoir can hold more than 2 million litres of water and was built before Newcastle had electricity. Work will need to be carried out to make it safe for the public before it is opened up for tours.

Over the next few months, stairs and lighting will be installed, and ventilation improved.

Hunter Water's managing director Kim Wood said the tours would offer more than a look inside.

"In addition to allowing the public to climb down into the belly of the reservoir, the tour will include a history of the Hunter's original water supply and reveal a glimpse of life in the late 1800s," Mr Wood said.

The tour will also give an insight into the construction of the reservoir and the original Walka Water Scheme, the first in the Hunter to deliver fresh water straight to people's homes.

■ Go to hunterwater.com.au to sign up to the reservoir tour ballot. Go to newcastlestar.com.au to see a photo gallery from the reservoir media tour.