The southbound Waterview tunnel will be closed next week, a fortnight after the northbound lanes were closed for scheduled maintenance work.
The southbound tunnel will closed from 10pm to 5am on Monday, Tuesday and Wednesday next week.
The closures come only weeks after the $1.4 tunnel opened on July 2, attracting more than 400,000 vehicles a week, cutting travel times to the airport and removing cars off local roads.
A New Zealand Transport Agency (NZTA) spokeswoman said there was chance of a third full tunnel closure before the agency works out a less disruptive maintenance schedule.
"Everyone is still learning the system," said the spokesman, saying ongoing maintenance is vital to keeping the tunnel operating safely and efficiently.
She said the maintenance of the Waterview tunnel would become similar to the maintenance closures in place for the Victoria Park and Johnstones Hill tunnels with two of the three lanes closed during the night either monthly or every three months.
The schedule of maintenance for Waterview is a 50-page document that requires checking and testing the electronic equipment like smoke detectors, fire hydrants and deluge systems. These are required by the building code and also required by the manufacturers to ensure the equipment keeps working. In many cases it is designed to last up to 25 years, the spokeswoman said.
The internal walls will be cleaned every four to six months.
"We understand that any closures of either the tunnel completely or lane closures can be frustrating for customers but keeping the tunnel well maintained is really important," the spokeswoman said.
Checks being carried out at Waterview include:
Fire hydrants. These are every 50 metres. Monthly checks required by the Building Code.
Deluge checks and diesel pump checks. There are 173 deluge zones, each 30 metres long. A couple of deluge zones will be tested during each maintenance closure. This will help to help to remove any spills or leaks on the road surface and help to keep the tunnel's road surface looking clean.