Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Sanitary Piping - Drainage Fixtures Unit Loads

Sponsored Links

The relationship between volume flow and fixture units is not constant, but varies with the number of fixture units. A Fixture Unit is not a flow rate unit but a design factor based on the rate of discharge, time of operation and frequency of use of a fixture. A fixture unit is equal to one cubic foot of water drained in an 1 1/4 pipe over one minute (≈ 7.48 US gpm, ≈ 0.47 l/s).

Maximum Drainage Fixture Units (DFU) in Stacks and Horizontal Fixture Branches

Drainage Fixture Units (DFU) in Stacks and Horizontal Fixture Branches
Pipe SizeMaximum Drainage Fixture Units (DFU)
Horizontal fixture branchStacks3) less than three stories in heightStacks more than three stories high
Total for stackTotal 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

3) Stacks - vertical runs of plumbing waste or drainage lines

The values are based on the major US plumbing codes.

Maximum  Drainage Fixture Units (DFU) in Building Drains and Building Drain Branches from Stacks

Drainage Fixture Units (DFU) in Building Drains and Building Drain Branches from Stacks
Pipe SizeMaximum Drainage Fixture Units (DFU)
Slope (in/ft (cm/m))
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
Sponsored Links

Related Topics

Sanitary Drainage Systems

The purpose of the sanitary drainage system is to remove effluent discharged from plumbing fixtures and other equipment.

Related Documents

ASTM B306 Copper Tubes for Drain, Waste and Vent - Dimensions and Working Pressures

Dimensions of copper tubes ASTM B306 Drain Waste and Vent - DWV.

ASTM D2729 - Poly(Vinyl Chloride) (PVC) Sewer Pipe - Dimensions

Dimensions of Poly(Vinyl Chloride) (PVC) Sewer Pipes with belled end.

Cast Iron Soil Pipes - Dimensions

Dimensions of cast iron soil pipes.

Cleanouts in Draining Systems

Cleanouts provides access to the sewer for rodding.

DFU - Drainage Fixture Units

DFU are used to calculate the drainage flow from fixtures and the required capacities of sewer service systems.

Drain Pipes and Vent Stacks

Drain pipes and vent stack sizing.

Drain Waste and Vent Pipes - Hanger Spacing

Support of Drain Waste and Vent - DWV - pipes.

Draining Systems - Main Vents

Vents in draining systems protects traps against pressure differences that could cause them to siphon or blow out .

Drains and Sewers - Capacities vs. Size

Drainage Fixture Units (DFU) connected to building drains and sewers.

Fixtures Trap Sizes

Recommended drain trap sizes for different types of fixtures

Horizontal Drainage Pipe - Required Slopes

Minimum pitch of horizontal drainage pipes.

Plumbing Codes

Plumbing or sanitation codes are a set of rules and regulations imposed by cities, counties or states.

Sanitary Drainage Systems - Volume Flow

Calculate expected volume flow load in sanitary drainage systems.

Septic Systems

Septic systems handles waste from drain systems.

Sewer Pipes - Capacities vs. Slope

Carrying capacities of sewer and wastewater pipes - gpm and liter per second.

Trap Sizes vs. Fixture Units

No. of fixture units and required trap size.

Waste Water Piping - Flow Capacities vs. Dimensions

In sewage piping and pumping systems the fluid flow rate must be kept within certain limits to avoid operating problems.

Water Supply due to Fixtures Water Requirements

Supply requirements for common fixtures.

Water Supply Fixture Units - WSFU vs. GPM and Liters/sec

Converting WSFU - Water Supply Fixture Units - to GPM.

Water Supply Fixture Units WSFU

WSFU is used to calculate water supply service systems.

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.