TL;DR
A backwater valve is a one-way flap valve installed in a building's sewer line that swings shut when the municipal sewer surcharges, blocking sewage from flowing backward into basement drains, toilets, and showers. It is the primary defense for homes with fixtures below the street sewer grade, and many flood-prone cities now require or subsidize one.
What it means
A backwater valve is a one-way flap valve installed in a building's sewer line that swings shut when the municipal sewer surcharges, blocking sewage from flowing backward into basement drains, toilets, and showers. It is the primary defense for homes with fixtures below the street sewer grade, and many flood-prone cities now require or subsidize one. Codes (IPC 715) limit it to protecting only fixtures below the upstream manhole cover, leaving upper floors free-draining. The flap needs an accessible cleanout and an annual check, since debris that props it open defeats the protection.
Where it sits in the glossary
Backwater valve 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
License: CC-BY-4.0 — quote freely with attribution to ProFix Editorial Team / ProFix Directory.