Fletcher Building's dismissing claims from west Australian builder BGC about problems caused by its Iplex Pro-fit pipes.

Fletcher has doubled down on its belief installation issues with the pipes causes them to leak in some 15,000 Perth homes.

BGC alleges the pipes are the issue and says fixes will cost an estimated $1.92 billion dollars.

Fletcher CEO Ross Taylor told Heather du Plessis-Allan they've done a huge number of tests that disproves BGC's theory.

“What we’ve seen there is in all instances where a leak’s occurred, is a 100 percent correlation between that leak and an installation problem.”

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