Drainage Fixture Unit Loads for Sanitary Piping

Maximum Drainage Fixture Unit - DFU - Loads for sanitary piping

The maximum permissible Drainage Fixture Unit (DFU) loads for sanitary piping can be estimated with the table below.

Maximum Drainage Fixture Units - Stacks and Horizontal Fixture Branches

Maximum Drainage Fixture Units (DFU)
Pipe Size Horizontal fixture branch Stacks less than 3 stories in height Stacks more than 3 stories high
NPS
(inches)
DN
(mm)
Total for stack Total for one story
1 1/20) 40 3 4 8 2
20) 50 6 10 24 6
2 1/20) 65 12 20 42 9
3 80 201) 481) 722) 201)
4 100 160 240 500 90
5 125 360 540 1100 200
6 150 620 960 1900 350

0) No water closet permitted

1) Maximum two water closets

2) Maximum six water closets

Maximum Drainage Fixture Units - Building Drains and Building Drain Branches from Stacks

Maximum Drainage Fixture Units (DFU)
Pipe Size Slope in/ft (cm/m)
NPS
(inches)
DN
(mm)
1/4 (2.1) 1/2 (4.2)
20) 50 21 26
2 1/20) 65 24 31
3 80 421) 501)
4 100 216 250
5 125 480 575
6 150 840 1000

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  • Water Systems - Hot and cold water systems - design properties, capacities, sizing and more

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