Water + Drainage Fixture Unit Calculator
Total the water supply fixture units and drainage fixture units for a building, and size the building drain that has to carry them.
WSFU and DFU are different systems that happen to share a name. Supply units feed a demand curve to size pipe and meter; drainage units feed a table to size the drain and its slope. Mixing them is the most common error in a plumbing submission.
What the plan reviewer checks
Fixture unit values differ between code editions and between adopting jurisdictions, so the table is editable here rather than fixed – set it to the edition your city actually enforces.
Need the whole set drawn and stamped? Ask for a fixed quote, or see the other calculators.
Complete MEP permit set built to get approved.
Every mechanical, electrical, plumbing, and fire sheet your reviewer needs — a fixed quote in 24 business hours, first sets in as few as 5 working days, and city comments answered until your permit is issued.