13.1 Washington's Amendments to the 2015 UPC (WAC 51-56): A Consolidated Review
Key Takeaways
WAC 51-56-003 adopts the UPC with Appendices A, B, and I, but not Chapters 12 and 14, the Chapter 5 venting and combustion air provisions, or the building sewer provisions.
Washington requires 24 inches in front of water closets and bidets, reduced to 21 inches in dwelling and sleeping units, and a 900-square-inch shower with a 30-inch circle.
Washington requires 12 inches of clearance in front of cleanouts 2 inches and smaller, 18 inches for larger cleanouts, and under-floor cleanouts within 20 feet of an access opening.
Washington requires an air gap or RP on boiler makeup water and a listed RP on carbonated beverage dispensers.
Washington defines hot water as 100°F or more and requires seismic strapping on every water heater, with 4 inches between the controls and the lower strap.
The Exam Edition and the Field Edition
- Exam: L&I and PSI state that the plumber examinations are based on the 2015 Uniform Plumbing Code with the Washington amendments. PSI's July 2026 bulletin still lists the 2015 UPC with Washington amendments as the reference for the open-book pump exam.
- Field: WAC 51-56 now adopts the 2021 UPC, effective statewide March 15, 2024, with updated amendments. Several numbers changed in the field code, including 1.28 gpf water closets, 1.8 gpm showerheads, and faucet flow rates.
- Rule for studying: learn the 2015 UPC with the 2015-cycle amendments for the exam. Know the current field numbers so you are not confused on the job.
What Washington Does Not Adopt (WAC 51-56-003 and Chapter Amendments)
| Not adopted | What governs instead |
|---|---|
| Chapter 12, Fuel Gas Piping | The fuel gas provisions of the mechanical code |
| Chapter 14, Firestop Protection | The building code (WA 312.7) |
| Chapter 5 venting and combustion air (506.1–506.9, 507.6–507.9, 507.16, 507.18–507.22, 509, 510, 511) | The Mechanical Code |
| Building sewers: Chapter 7 Part II, Sections 713–723 and Tables 717.1 and 721.1 | Local sewer and health authorities |
| Table 422.1 and Sections 422.1–422.5 (fixture counts) | Building Code Chapter 29 and Table 2902.1 |
| 415.2 Drinking fountain alternatives | Building Code Chapter 29 |
| 1502 Gray water systems | Department of Health rules |
| 908.2.4 (water closet position on a horizontal wet vent) | No restriction |
| 612.2–612.7.2 Residential fire sprinklers | IBC or IRC (WA 612.1) |
| 1105 Controlled-flow roof drainage | Not adopted |
| Appendices other than A, B, and I | Not adopted |
Key Changes, Chapter by Chapter
| Chapter | Washington rule | Guide section |
|---|---|---|
| 1 | 102.1 deleted; 103.3.1 state certification rules (RCW 18.106) apply | 1.1, 1.2 |
| 2 | Hot water is 100°F or more; plumbing system includes water heaters and medical gas within property lines, with no certification needed outside the building; BAT is DOH-certified | 10.3 |
| 3 | 301.3 alternates: denials in writing; 312.6 insulate hot and cold pipes outside conditioned space (2015: R-3); 312.7 penetrations per building code | 1.3 |
| 4 | 402.5 clearances 24 in, 21 in in dwelling and sleeping units; 405.4 fixtures sold or installed must meet Chapter 4; 407.2 faucets 2.5 gpm, public lavatories 0.5 gpm; 407.4 metering faucets in public restrooms; 408.2 showerheads 2.5 gpm (2015 cycle); 408.4 tub-to-shower 1-1/2-inch exception; 408.6 shower 900 sq in plus 30-inch circle; 411.2 water closets 1.6 gpf; 412.1 urinals 1.0 gpf; 414.3 dishwasher air gaps; 418.3 floor drain locations | 2.1–2.4 |
| 5 | Table 501.1 first hour ratings 42–80 gal; 504.1 bedroom and bathroom closets; 505.2 non-gas heaters need an overtemperature device and T&P; 507.2 seismic straps for all heaters, 4 in from controls; 507.13 garage 18 in including ignition sources | 3.1–3.4 |
| 6 | 603.1 DOH-approved assemblies; 603.2 maintenance and BAT testing; 603.4.2 test at installation and annually; 603.5.6 irrigation DC only with purveyor and AHJ approval; 603.5.10 boilers air gap or RP; 603.5.12 carbonators RP; 604.14 plastic service termination; 606.5 manifolds; 608.3 expansion tanks (instantaneous exempt); 608.5 T&P discharge list with replacement exception; 609.9 disinfection 50 ppm for 24 hr or 200 ppm for 3 hr; 609.11 insulation per the energy code; 611.1 Group A water system note; 612.1 sprinklers per IBC or IRC | 1.2, 3.2, 3.4, 4.1–4.4, 5.1–5.4, 13.3 |
| 7 | 701.2 material limits; Table 703.2 note 4 exception (four 1.6 gpf water closets on 3-inch horizontal in single-family additions, AHJ approval); 704.3 direct connection; 707.4 cleanout locations; 707.9 clearances 12 and 18 in, 20 ft | 6.1–6.4, 7.1 |
| 9 | 903.1 vent material limits; 911.1 circuit venting: 8 fixtures, no restaurant kitchen equipment, back-outlet water closet exception | 8.1, 8.3 |
| 15 | 1501.1.1 no reclaimed water indoors in dwellings where residents can reach the plumbing; 1501.7 and 1504.7 Class A reclaimed quality for flushing; 1501.11.2.3 cross-connection discovery procedure; 1503.4 air-gap makeup | 10.1 |
| 16 | 1602.1 AHJ approval (exterior irrigation piping excepted); 1601.11.1 abandoned parts not reused for potable water; 1602.11.2.3 discovery procedure | 10.2 |
How These Amendments Show Up on the Exam
- Direct recall: "What is the minimum clear space in front of a water closet in a Washington apartment?" Answer: 21 inches.
- Trap answers: an option quoting the unamended UPC value, such as 1,024 square inches for a shower or 18 inches of cleanout clearance, is the wrong answer in Washington.
- "Not adopted" questions: "Where do Washington fixture counts come from?" Answer: Building Code Table 2902.1.
- Drawing effects: the note 4 exception and the cleanout amendments change Part 2 answers only in the situations they describe. Read the drawing notes for single-family addition language.
A 60-Second Memory Drill
21/24, 900, 12/18/20, 100°F, 4-inch strap gap, 18-inch garage, 50/24 or 200/3, air gap or RP for boilers, RP for carbonators, 8 circuit fixtures, no kitchen equipment, no sewers, no Chapter 12, no Table 422.1, no gray water. Each phrase maps to one row of the tables above.
Which UPC chapters does WAC 51-56-003 exclude from Washington's adoption of the Uniform Plumbing Code?
Chapter 17 only
Chapters 11 and 13
Chapters 12 and 14
Chapters 15 and 16
Under Washington's amendments, what minimum clear space is required in front of a water closet in a hotel sleeping unit?
18 inches
21 inches
24 inches
30 inches
Which statement about the Washington plumber exam's code edition is correct?
The exam is based on the 2024 UPC
L&I and PSI state that the exam is based on the 2015 UPC with Washington amendments, although the current field code adopts the 2021 UPC
The exam is based on the International Plumbing Code
The exam has no specific edition
Sections you finish are checked off in the contents.