Drainage Fixture Units
How Many DFUs Is a Clothes Washer?
A residential clothes washer is commonly counted as 3 DFUs under UPC-style assumptions and 2 DFUs under IPC-style assumptions. The correct value depends on the plumbing code adopted for the project, and DFUs alone do not determine the required standpipe, trap, vent, or branch-drain size.
| Fixture | UPC-style DFU | IPC-style DFU |
|---|---|---|
| Residential clothes washer | 3 DFUs | 2 DFUs |
These are planning values used throughout BuildCalc. Verify the applicable code edition and local amendments before final design or construction.
Quick answer: washing machine DFU
For early drainage planning, use 3 DFUs for a clothes washer under UPC-style assumptions and 2 DFUs under IPC-style assumptions. If several washers connect to the same branch or building drain, their fixture loads contribute to the total DFUs on that section of piping.
Compare the washer with toilets, showers, lavatories, kitchen sinks, floor drains, and other fixtures in the plumbing DFU chart.
UPC vs IPC clothes washer DFUs
UPC and IPC both use drainage fixture units to represent the approximate drainage load produced by plumbing fixtures, but they do not assign identical values to every fixture. Clothes washers are one of the fixtures where the planning values differ.
UPC-style assumption
Use 3 DFUs per residential clothes washer for the UPC-style planning calculations used on BuildCalc.
IPC-style assumption
Use 2 DFUs per residential clothes washer for the IPC-style planning calculations used on BuildCalc.
If you are unsure which code framework applies, review the UPC vs IPC plumbing code comparison and the state plumbing code lookup.
Clothes washer DFU examples
For a simple planning calculation, multiply the number of clothes washers by the applicable fixture-unit value.
| Clothes washers | UPC-style total | IPC-style total |
|---|---|---|
| 1 washer | 3 DFUs | 2 DFUs |
| 2 washers | 6 DFUs | 4 DFUs |
| 3 washers | 9 DFUs | 6 DFUs |
These totals estimate fixture load only. They do not automatically establish the required pipe diameter or prove that a particular drainage layout complies with the applicable plumbing code.
Washer plus laundry sink
A laundry room often contains more than the clothes washer. In the BuildCalc DFU chart, a laundry sink is represented as 2 DFUs under both UPC-style and IPC-style assumptions.
That gives a simple planning total of 5 DFUs under UPC-style assumptions or 4 DFUs under IPC-style assumptions for one clothes washer plus one laundry sink.
Multiple laundry fixtures
If a laundry area also contains a utility sink, floor drain, or other plumbing fixture, include those fixtures when estimating the total drainage load on the branch.
The DFU calculator is the easier way to total several fixture types and quantities.
DFUs do not determine the washer drain by themselves
A drainage fixture unit represents fixture load. It is not a complete specification for a washing-machine drainage system. The actual installation also has to account for the standpipe, trap, branch drain, venting, fittings, developed length, and the requirements of the adopted plumbing code.
After calculating all of the fixtures connected to a pipe section, compare the resulting load with the appropriate drainage sizing requirements rather than selecting pipe diameter solely from the washer's individual DFU value.
How washer DFUs affect downstream drainage
The clothes washer's fixture units become part of the total load as wastewater moves downstream. A branch serving a laundry room may eventually combine with bathroom, kitchen, or other drainage before reaching the building drain or building sewer.
If you are evaluating a larger drainage pipe, see the 3-inch pipe DFU guide. If you are evaluating the grade of a horizontal building drain or sewer, use the sewer slope calculator.
Clothes washer DFU calculation workflow
- Count the clothes washers connected to the pipe section.
- Determine which plumbing code applies to the project.
- Use 3 DFUs per washer for the UPC-style planning value or 2 DFUs per washer for the IPC-style planning value.
- Add any laundry sinks, floor drains, or other fixtures.
- Calculate the total drainage fixture-unit load.
- Verify pipe sizing, standpipe, trap, venting, and other installation requirements using the adopted plumbing code.
Frequently Asked Questions
How many DFUs is a clothes washer?
A clothes washer is commonly counted as 3 drainage fixture units under UPC-style assumptions and 2 drainage fixture units under IPC-style assumptions for planning purposes.
How many DFUs is a washing machine under the UPC?
A residential clothes washer is commonly estimated at 3 DFUs using UPC-style assumptions. Verify the adopted code edition and local amendments before final sizing.
How many DFUs is a washing machine under the IPC?
A residential clothes washer is commonly estimated at 2 DFUs using IPC-style assumptions. Final requirements should be checked against the code adopted for the project location.
Why are clothes washer DFUs different between UPC and IPC?
UPC and IPC do not assign identical drainage fixture unit values to every fixture. Clothes washers are one example where the planning value can differ, so the applicable plumbing code matters when calculating the total drainage load.
Can I size a washing machine drain from DFUs alone?
No. DFUs estimate drainage load, but a clothes washer installation also requires review of the standpipe, trap, branch drain, venting, pipe size, developed length, and applicable plumbing code.
Do multiple washing machines add their DFUs together?
For a simple planning estimate, multiply the applicable DFU value by the number of clothes washers connected to the pipe section being evaluated. Final sizing must still follow the adopted plumbing code.
Does a laundry sink add additional DFUs?
Yes. A laundry sink is a separate plumbing fixture and contributes additional drainage load. This DFU chart uses a planning value of 2 DFUs for a laundry sink under both UPC-style and IPC-style assumptions.
Important reminder
These DFU values are intended for education and early planning. Verify the applicable plumbing code, local amendments, standpipe and trap requirements, venting, pipe sizing, and inspection requirements before construction.
Compare Other Fixture DFU Values
Compare the clothes washer with toilets, lavatory sinks, showers, kitchen sinks, bathroom groups, and other common plumbing fixtures.
Toilet DFU
Common toilet fixture-unit values for private-use and public-use water closets.
Lavatory Sink DFU
Bathroom sink DFU values and how lavatories fit into bathroom fixture groups.
Shower DFU
Typical shower fixture-unit values, including notes for larger or custom showers.
Bathroom DFU
DFU examples for half bathrooms, full bathrooms, and bathroom groups.
DFU Chart
Fixture unit chart for toilets, sinks, showers, tubs, washers, and floor drains.
Need help reviewing clothes washer DFUs or drain sizing?
Send the number of clothes washers, any connected laundry sinks or floor drains, the pipe size, and your code question. BuildCalc can help organize your clothes washer DFU and drainage sizing review.
Continue with DFU and drainage resources
Use these related tools and guides to total fixture loads, compare pipe sizing, and evaluate downstream drainage requirements.
ADU Plumbing DFU Guide
Plan DFU loads for an accessory dwelling unit with bathroom, kitchen, laundry, and drainage fixtures.
DFU Calculator
Calculate drainage fixture units for common plumbing fixtures and estimate pipe sizing needs.
Toilet DFU Guide
Understand how toilets affect DFU totals, branch drains, building drains, and sewer sizing.
Lavatory Sink DFU Guide
Understand common lavatory sink drainage fixture unit values and how bathroom sinks affect DFU totals.
Shower DFU Guide
Understand common shower drainage fixture unit values and how showers affect bathroom DFU totals.