A water main has burst in Porirua, causing outages in the city centre, Rānui, and Elsdon.

A 300mm main burst on Mepham Place around 2:20pm, causing the asphalt to crack.

"At this stage, there is no estimated timeframe for full restoration, but it is anticipated that service will be interrupted for at least eight hours," mayor Anita Baker said.

Pātaka Art + Museum, Café Kaizen, Porirua Library, and Te Rauparaha Arena and Aquatic Centre have all closed as a result of the burst water main.

Tiaki Wai expected water to return from around 10:30pm on Saturday night.

It has established an incident management team to begin the excavation process around the burst water main.

A water tank has been ordered for affected residents and will be located on the corner of Mepham Place and Champion Street.