Illinois Plumbing Code

Illinois plumbing work is governed by the Illinois Plumbing Code, 77 Ill. Adm. Code 890, a state-written code that follows neither the IPC nor the UPC.

Confirm the current edition before you size

We deliberately do not state an edition year here. Editions change on three-year cycles and states adopt on their own schedule, so a stale year is the most common way this kind of reference goes wrong — and sizing against the wrong edition fails plan review. Confirm the edition in force with the Illinois Department of Public Health (IDPH).

Adopted Code

Item	Value	Source
Code document	Illinois Plumbing Code, 77 Ill. Adm. Code 890	Model knowledge, May 2026. Code family and authority only — confirm the current edition with the authority named.verified 2026-09-25
Based on	State-written (neither IPC nor UPC)	Model knowledge, May 2026. Code family and authority only — confirm the current edition with the authority named.verified 2026-09-25
Authority	Illinois Department of Public Health (IDPH)	Model knowledge, May 2026. Code family and authority only — confirm the current edition with the authority named.verified 2026-09-25

Local jurisdictions may amend the state code further. Always confirm with the authority having jurisdiction before submitting for permit.

How the Illinois Code Is Organised

The Illinois Plumbing Code is 77 Ill. Adm. Code 890, a state-written administrative rule rather than an adaptation of a model code. It is organised as a regulation, cited by Section number, and it carries its own fixture unit schedules, pipe sizing tables and venting provisions. Neither IPC nor UPC chapter references map onto it, so an IPC-trained designer cannot navigate it by analogy.

What It Changes About Sizing

Because the code is state-written, sizing must come from the Illinois tables directly. Fixture unit values assigned to common fixtures differ from IPC values, so the same building produces a different demand total and therefore a different pipe size. Importing an IPC calculation and adjusting it is not a shortcut here; it produces numbers that do not correspond to any Illinois table.

Licensing in Illinois

Illinois licenses individual plumbers, not just contracting businesses, and does so through the Department of Public Health. The apprentice, licensed plumber and plumbing contractor tiers are administered together with the code itself, which means the same agency that writes the sizing rules also examines the people applying them. Sponsorship by a licensed plumber is required to enter the apprenticeship.

Cities That Do Something Different

Chicago enforces its own municipal plumbing code and is the significant carve-out. Work inside the city is reviewed against the Chicago code, not 77 Ill. Adm. Code 890, and Chicago has historically been more restrictive on materials than the state. Designers working across the metropolitan boundary are effectively working under two codes.

What Out-of-State Contractors Get Wrong in Illinois

1Sizing from IPC or UPC tables. Illinois values differ and plan review checks against 77 Ill. Adm. Code 890.
2Submitting Chicago work against the state code, or state work against the Chicago code. They are separate documents.
3Looking for the code in a building department. Illinois administers plumbing through the Department of Public Health, so the plan review channel is different from most states.
4Assuming a contractor licence covers the individuals doing the work. Illinois licenses plumbers individually.

Illinois in Practice

Administered by the Department of Public Health rather than a building department, which means plan review and inspection run through a different channel than in most states.

Because the code is state-written, IPC and UPC sizing tables do not transfer. Fixture unit values and pipe sizing must come from 77 Ill. Adm. Code 890 itself.

Chicago enforces its own municipal plumbing code separately from the state code.

Illinois writes its own plumbing code rather than adopting IPC or UPC, and administers it through the health department rather than a building department. Sizing tables differ from both model codes.

Our sizing calculators state the edition and table they use: pipe sizing, drainage slope, gas line sizing. Check them against the IL edition in force before relying on a result.

Code References & Best Practices:

Place of record for Illinois: Illinois Department of Public Health (IDPH). Confirm the edition in force there.
Licensing in Illinois is administered by the Illinois Department of Public Health (IDPH).
Provenance: Model knowledge, May 2026. Code family and authority only — confirm the current edition with the authority named.