ID Plumber study guide
ID Plumber · Work through your exam, one topic at a time.
The Idaho plumber credential is a state-issued license that lets you legally perform plumbing work in Idaho, and it comes in tiers: journeyman, master, and contractor-level registration. It is for apprentices finishing supervised hours, out-of-state plumbers seeking reciprocity, and anyone preparing to run or supervise plumbing work in the state. The ID Plumber study guide has 9 sections and about 3,523 words.
01General Plumbing Regulations, Definitions, and Administration
Idaho plumbing is regulated by the Idaho Plumbing Board within the Division of Building Safety (DBS). Questions come from three layers: the licensing statute, the Board's adopted rules, and the Uniform Plumbing Code (UPC) as amended for Idaho.
430 words, about 2 min02General Building and Plumbing Code Provisions
The general regulations chapter is where plumbing meets structure. Pipes must be supported at code intervals - commonly cited maximum horizontal spacing is 4 feet for ABS/PVC, 5 feet for cast iron, 6 feet for copper 1¼ inch and smaller, and 10 feet for larger copper - with vertical piping supported at each story.
406 words, about 2 min03Fixtures, Fixture Fittings, and Water Heaters
Fixture questions test dimensional rules and approvals. A water closet is set with its centerline at least 15 inches from a sidewall or partition and at least 15 inches from a bathtub or shower, with code-required clear space in front; adjacent water closets are typically spaced 30 inches on center.
424 words, about 2 min04Water Supply and Distribution
The supply chapter is mostly about pressure, sizing, and backflow. Static pressure above 80 psi at any fixture requires a pressure-reducing valve; residual pressure must still satisfy the most remote fixture, with tank-type fixtures needing less than flushometer valves.
381 words, about 2 min05Sanitary Drainage, Vents, and Storm Drainage
Slope is the first check: ¼ inch per foot for pipe 2½ inches and smaller, ⅛ inch per foot for 3 inches and larger. Drainage fixture units come from the tables and are accumulated from fixture to branch to building drain.
414 words, about 2 min06Traps, Interceptors, and Special Wastes
A trap seal is 2 to 4 inches deep; deeper seals need additional protection against siphonage. Each fixture is separately trapped except for listed combinations, and certain traps are prohibited: S-traps, bell traps, drum traps with mechanical seals, crown vents, and two fixtures sharing one trap.
371 words, about 2 min07Indirect and Special Wastes; Gray Water and Reclaimed Water
An indirect waste connection discharges through an air gap or air break into a receptor; it is never piped directly into the drainage system. The receptor is sized for the discharge and the gap is maintained above the flood level rim.
370 words, about 2 min08Fuel Gas Piping and Appliance Connections
Gas sizing uses the longest-length method: measure from the meter to the most distant appliance, add the developed length of that run (including fittings allowance), and enter the sizing table with the total connected load. Convert Btu/h to cubic feet per hour by dividing by the heating value of the gas, roughly 1,000 Btu per cubic foot for natural gas.
384 words, about 2 min09Plumbing Math, Sizing Calculations, and Plan Reading
1 cubic foot = 7.48 gallons; 1 gallon of water weighs 8.34 pounds. 1 psi = 2.31 feet of head; 1 psi is about 27.7 inches of water column.
343 words, about 2 min