A major plumbing company is now facing court action over Wellington Hospital's mass of leaking pipes.
The High Court in Wellington has ruled to include Mico Plumbing in the case, because it imported the copper pipes, and legally is seen as the pipes' manufacturer.
The Capital and Coast District Health Board is suing another four other defendants as well, including the lead contractor Fletcher Construction and consulting engineers Beca.
The DHB claims Mico breached guarantees because the pipes should last at least 50 years but are failing after a decade, the court ruling shows.
"It says 300 leaks have been found in the copper pipes so they have failed and require replacement," the ruling said.
"The copper pipes have developed 'pin hole' type leaks which are sufficiently serious to require the whole system to be replaced", according to the DHB, though the cause would be argued in court.
An earlier ruling says the DHB claims there were eight separate defects in both the design and the construction of the hot and cold water system in the main hospital building.
The $140 million hospital rebuild was finished in 2008. In 2016 RNZ broke the story of the leaking pipes.
Fletchers opposed Mico being included but the judge said its point that the copper pipes were not "goods" under law was arguable.
Legal action has been dropped against at least 10 other companies, including Crane Group in Australia, though its subsidiary Crane Enfield Metals, that made the pipes, is still a target.
Mico as the importer is deemed to be a manufacturer under the Consumer Guarantees Act.
The alleged design defects include gas bubbles forming in the water being carried through the pipes created by turbulence and changes in pressure, temperature and cross-section; and concealing the pipe in walls and ducts where it is hard to maintain.
The DHB claims there was general negligence by Fletchers, though the design was mostly the responsibility of Beca, and that Crane Enfield Metals manufactured or supplied the copper pipes with the defects.