In a rare site, a tank that usually holds 56 megalitres (or 22 Olympic swimming pools) of water has been completely drained as SA Water begin maintenance on the structure.
It's one of two water storage tanks in Whyalla that supply water to thousands of customers in the area, including the local steelworks.
The tank was drained in a planned manner, with SA Water allowing the water level to fall to a low level and then pumping the rest of the liquid into the second tank - which remains online.
Maintenance on the tank is being undertaken by approximately 50 people from contractors Fulton Hogan, with work including concrete rehabilitation, a new overflow pipework, new external concrete drains, new roof beams and around 5000 square metres of roof re-sheeting.
Due to the enormous size of the tank, a 100 tonne crane is being used to lift and fit the new roof sheeting panels into place.
SA Water General Manager Asset Operations and Delivery Mark Gobbie said the maintenance would not impact on the water supply to Whyalla.
"While the tank remains offline our customers can rest assured that having the existing tank in operation means there is no impact to the water supply as part of this refurbishment," he said.
Water stored in the tank comes via the Morgan-Whyalla pipeline. The storage facility is the last stop for the water before it is pumped into Whyalla.
SA Water Technical Support Officer Liam Tothill said the tank was a critical piece of infrastructure for the town's water supply.
"The work we're doing here is important to ensure that we are providing a reliable water supply to Whyalla. It's part of the routine maintenance of our infrastructure," he said.
Restorations to the 77-metre-diametre tank forms part of SA Water's $89 million investment to refurbish 111 water storages around South Australia between 2016 and 2020.
The tank is expected to be back in operation come September.