As part of the major rehabilitation of the building systems at Prague we recommended epoxy lining only for waste piping, not domestic supply, which is typically too narrow or otherwise compromised as has already been pointed out.
The method is useful where piping is buried in concrete or masonry construction behind valued finishes. We have used it for repair of storm water piping in similar hidden construction at the Washington State Legislative Building.
We specify camera inspection before and after installation, take samples to check remaining pipe thickness, and replace accessible sections in poor repair. The piping at Prague was of fine quality and generally in good condition but 80 years old. The client did not want to face another rehabilitation for another generation or two, so we recommended this intervention to prolong the life of a good quality system.
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Christopher Tavener AIA
EYP Architecture & Engineering -------------------------------------------