A huff, and a puff and Napier's pipes are clean

A Napier City Council crew on watermains cleaning duty. Photo / Supplied

It sounds like a lot of pigs but 300 is what's needed to clean up a pig sty – the inside of the 460 kilometres of pipes delivering water to the 60,000 people of Napier.

Biofilm clings to the inside of the pipes and Cr Richard McGrath, who works closely with the council's depot team, says: "It's organic and harmless but pretty grotty, so it's got to go."

Enter the porcine-identified innovation – 300 foam squabs called "pigs" on a 10-week attack on the city's underground entrails.

Council staff say the "pigs" will be sent "flying" through the pipes to give them a thorough clean, hoping to have most of them clean as a whistle by Labour Day, when the project will end come hell or high water as the city starts switching to summer water restrictions.

As it happens it's going with the flow, for the process is an annual event, with McGrath saying water mains cleaning is an important way to maintain Napier's pipe network.

"Getting clean water into households is a priority for us and we've got to look after our system to make sure we can do that," he says. "Our pigs scrub off the biofilm that clings to the inside of the pipes. It's organic and harmless but pretty grotty so it's got to go."

Households may experience some discoloured water during the cleaning, and some temporary loss of water supply. Residents are notified ahead of the running of the pigs in their areas, with letter to each home and messages broadcast across the airwaves, on Newstalk ZB, The Hits, Gold and Coast. A letter is also delivered to each affected home.

The "pigs" have a four-day week, from Tuesday to Friday, taking Saturday to Monday off each week.