Illinois Plumbing Code
What the exam tests
This domain tests your ability to apply the Illinois Plumbing Code, 77 Ill. Adm. Code 890, to field decisions: permits, inspections, drainage, venting, water supply, fixtures, and materials. Questions usually ask which code rule controls an installation, not just what a term means.
Core rules
- A permit is required before new plumbing, alteration, extension, or replacement unless the code or local ordinance exempts a minor repair. Work must be performed by a licensed plumber under a licensed plumbing contractor.
- Rough-in and final inspections are separate. Concealed work must be inspected before it is covered.
- Horizontal drainage slope: 1/4 in/ft for 2 1/2 in and smaller; 1/8 in/ft for 3 in through 6 in; 1/16 in/ft for 8 in and larger.
- Each fixture needs a trap, except fixtures with integral traps. Trap seal is 2 to 4 in, and each trap needs a vent.
- Maximum trap-arm distance to vent: 1 1/4 in = 2 ft 6 in; 1 1/2 in = 3 ft 6 in; 2 in = 5 ft; 3 in = 6 ft; 4 in = 10 ft.
- Water supply pipe is sized from fixture units and available pressure. Lead pipe, solder, and flux are prohibited.
Worked example
A 2 in lavatory drain runs 6 ft horizontally before reaching its vent. The maximum trap-arm length for 2 in is 5 ft, so the installation fails. The fix is not to enlarge the drain; it is to move the vent or add a re-vent so the trap arm stays within 5 ft. At rough-in, the inspector checks slope, trap seal, vent, and support.
Traps
Using 1/8 in/ft slope on a 2 in drain; measuring the trap arm from the wrong point instead of trap weir to vent; treating a cleanout as a vent; installing a fixture without a trap; covering work before inspection.