Washington's journey-level exam is written against the 2015 UPC with Washington amendments. Under that edition's Washington text, what is the maximum water use per flush for a standard (non-exempt) water closet?
Not quite. The answer is C: 1.6 gallons per flush
In the 2015-edition Washington code the standard cap is 1.6 gallons per flush, matching the federal limit; 3.5 gpf appears only as an exception for day-care toilets, bedpan washers and blow-out bowls. The code Washington enforces on the job today is stricter: the 2021-edition Washington amendment (effective March 15, 2024) lowers the cap to 1.28 gpf and requires WaterSense-level performance. A plumber working from a current code book will see 1.28, so know which edition a question is asking about.
Reference: WAC 2015 51-56-0400, §411.2 (2015-edition amendments) (Water closet flush volume — 1.6 gpf (2015 basis) vs 1.28 gpf (2021, in force since 2024-03-15))
Checked against the official text
Edition conflict: the exam's 2015 basis allows 1.6 gpf; Washington's enforced 2021 code caps standard water closets at 1.28 gpf.