The failure of a plumbing company won't void warranties on troublesome pipes at a half-billion-dollar Christchurch Hospital project.

The Australian-owned PHP NZ was placed in liquidation last week.

The Health Ministry has had to investigate its work after PHP used pipes not approved by the engineer at the acute-care building, New Zealand's largest hospital project.

Another firm, Hanlon Plumbing, had been working with PHP and the main contractor, CPB, for some time, the ministry said.

"Hanlon will be providing warranty for the majority of the pipework, CPB will warrant the remainder," it said in a statement.

Most of the non-compliant plastic pipe has been replaced, and work continues replacing other non-compliant pipes.

"It's important to note, this pipework is not defective or of low quality - the pipes were deemed non-conforming due the requirement to have only one system in the building to allow ease of maintenance and spare parts.

"The Ministry has undertaken an audit to confirm the [new] pipework meets the specifications in the Building Code."

All pipework had the Watermark certification, it said. Watermark is an Australian plumbing quality system - New Zealand lacks such a system of its own.

The hospital project has been beset by problems with materials and workmanship and is 16 months behind schedule.

The plumbing company liquidation would have no impact on budget, timing, or the quality of the job, the ministry said.

"Given the project's size and complexity, it's standard practice that non-conformance notices are issued on a regular basis to ensure quality is maintained, and compliance with project specifications."