TL;DR
Copper Type M is the thinnest-wall grade of copper water tube sold for plumbing, printed in red, used for interior above-grade supply lines where codes allow it. The lighter wall makes it the cheapest copper option and perfectly serviceable on clean municipal water, but some jurisdictions and many plumbers exclude it for underground runs, and aggressive or acidic water eats through it years sooner than heavier grades.
What it means
Copper Type M is the thinnest-wall grade of copper water tube sold for plumbing, printed in red, used for interior above-grade supply lines where codes allow it. The lighter wall makes it the cheapest copper option and perfectly serviceable on clean municipal water, but some jurisdictions and many plumbers exclude it for underground runs, and aggressive or acidic water eats through it years sooner than heavier grades. Checking the printed color line tells you instantly which grade a repipe actually delivered.
Where it sits in the glossary
Copper Type M is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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