DFU - Drainage Fixture Units

DFU (Drainage Fixture Unit Values) calculator based on the Uniform Plumbing Code (UPC). Used to calculate drainage flow from fixtures and determine required capacities of sewer service systems. A fixture unit equals one cubic foot of water drained in a 1 1/4" pipe over one minute (≈ 7.48 U.S. gpm, ≈ 0.47 l/s).

Fixture Type	Trap Size (in)	DFU Value	Flow Rate (l/s)
Bathtub	1 1/2	2	0.9
Bidet (1 1/4)	1 1/4	1	0.3
Bidet (1 1/2)	1 1/2	2	-
Dishwashing machine, domestic	1 1/2	2	0.6
Drinking fountain	1 1/4	0.5	0.1
Floor drain, 3"	3	6	-
Floor drain, 4"	4	8	2
Shower	2	2	0.4
Laundry tub	1 1/2	2	-
Lavatory	1 1/4	1	-
Kitchen sink, domestic	1 1/2	2	-
Laundry sink	1 1/2	2	-
Mobile home, trap	3	12	-
Urinal	2	2	0.3
Water Closet, gravity tank	3	3	1.8
Water Closet, flushometer valve	3	3	-
Water cooler	1 1/4	0.5	-
Clothes washer, residential	2	2	-
Clothes washer, commercial	2	3	-
Bathroom (complete)	3	6	-

Calculator

Inputs

Fixture 1

Quantity

Fixture 2

Quantity

Fixture 3

Quantity

Results

Total DFU-- DFU