TL;DR
A drainage fixture unit (DFU) is the plumbing code's unit for the probable wastewater load a fixture puts on the drain system — a lavatory counts as 1, a toilet as 3 or 4 depending on flush volume. Plumbers total the DFUs served by each pipe and read the required diameter from code tables, so the number drives drain and building-sewer sizing.
What it means
A drainage fixture unit (DFU) is the plumbing code's unit for the probable wastewater load a fixture puts on the drain system — a lavatory counts as 1, a toilet as 3 or 4 depending on flush volume. Plumbers total the DFUs served by each pipe and read the required diameter from code tables, so the number drives drain and building-sewer sizing. Septic designers use the same totals when sizing tanks for unusual homes.
Where it sits in the glossary
Drainage fixture unit 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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