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

DFU - Drainage Fixture Units

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

DFU (Drainage Fixture Unit Values) is defined by the the Uniform Plumbing Code (UPC) and can be used to determine required drainage capacities from fixtures and their service systems.

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).

DFU - Drainage Fixture Units
Individual Appliance, Appurtenance or FixtureMinimum Size of TrapDrainage Fixture Unit Values
(DFU)
Typical Values used in Europe
(inch)Private InstallationsPublic Installations(l/s)
Automatic clothes washers, commercial 2 3
Automatic clothes washers, residential 2 2
Bathroom (water closet, lavatory, bidet and tub or shower) 3 6 -
Bathtub 1 1/2 2 2 0.9
Bidet 1 1/4 1   0.3
Bidet 1 1/2 2  
Clothes Washer 2 3 3
Dental unit, cuspidor 1 1/4 1
Dental lavatory 1 1/2 1
Dishwashing machine, domestic 1 1/2 2 2 0.6
Drinking fountain 1 1/4 0.5 0.5 0.1
Floor drain, 3" 3 6 6
Floor drain, 4" 4 8 8 2
Food waste disposer 2 3
Shower 2 2 2 0.4
Laundry tub 1 1/2 2 2
Lavatory 1 1/4 1 1
Bar sink 1 1/2 1  
Kitchen sink, domestic 1 1/2 2 2
Laundry sink 1 1/2 2 2
Mobile home, trap 3 12
Service or mop basin 2   3
Sink, bar 1 1/2 1 0.3
Sink, clinical 1 1/2 2
Sink, commercial with food waste 2 3
Sink, kitchen domestic 1 1/2 2 2 0.6
Sink, laundry 1 1/2 2 2
Sink, service mop basin 2 3 0.9
Urinal 2 2 2 0.3
Washfountain 1 1/2 2
WC - Water Closet, gravity tank 3 3 4 1.8
WC - Water Closet, flushometer tank, valve 3 3 4
Water cooler 1 1/4 0.5 0.5

Fixture Units are used in plumbing design for both water supply (WFSU) and waste water (DFU).

Since the fixtures in a system are never used all at the same time, the total units (capacity) achieved by adding the numbers for all fixtures must be compensated for intermittent use if we want a realistic estimate of the total drainage load.

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

Search

Search is the most efficient way to navigate the Engineering ToolBox.

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

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 older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

Citation

This page can be cited as

  • The Engineering ToolBox (2009). DFU - Drainage Fixture Units . [online] Available at: https://www.engineeringtoolbox.com/drainage-fixture-unit-values-d_1077.html [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter

















































4.10.13

.