St. Louis County Plumbing Exam Fees and IAPMO Fee Increases

IAPMO Exam Fees Are Rising Through January 2027

If you're planning to test for your journeyman or master plumber license in St. Louis County, timing matters. The county's exam vendor, IAPMO, has scheduled three waves of fee increases running through January 1, 2027. Waiting to take the exam costs you real money — and the increases are substantial.

St. Louis County is one of the few Missouri jurisdictions that administers its own proprietary exams rather than accepting standard ICC scores. The Board of Plumbing Examiners contracts with IAPMO for both written and practical testing. That vendor relationship means the county's testing costs operate on a different schedule from ICC-based jurisdictions like St. Charles County or Jefferson City.

The Fee Escalation Schedule

Here's what the three-wave increase looks like across exam categories:

Journeyman Written Exam (Online/FLEX): The baseline of $150 rises to $175 effective July 1, 2026, and holds at $175 through January 1, 2027.

Journeyman Written Exam (In-Person): Starts at $200, increases to $235 as of July 2026, then climbs to $250 in January 2027.

Journeyman Practical and ISO Exam: The baseline of $145 jumps to $190 in July 2026 and reaches $225 by January 2027 — a 55% increase from the starting point.

Master Written Exam (Online/FLEX): Goes from $175 to $210 in July 2026, then to $250 by January 2027.

Master Written Exam (In-Person): The steepest climb — $225 at baseline, $275 in July 2026, and $325 by January 2027.

Master ISO Exam: From $110 to $145 in July 2026, then $175 in January 2027.

What This Means for Your Budget

A master plumber candidate taking both the written in-person exam and the ISO practical before July 2026 pays $335 total. After January 2027, the same two tests cost $500 — a $165 increase for the same credential.

For journeyman candidates who need both the written and practical exams, the total goes from $345 at baseline to $475 after January 2027.

These fees cover only the IAPMO exam itself. You still need to pay the board's license card fee ($30 for either journeyman or master) and cover any retake costs if you don't pass on the first attempt. Confirm the current retake fee with IAPMO.

Online vs. In-Person: The Cost Difference

IAPMO offers a FLEX (online) option for the written portion of both journeyman and master exams. The online format runs $50-$75 cheaper than in-person testing at every price point. If you're comfortable with proctored online testing, the savings are significant — especially at the 2027 rate, where the master written in-person exam costs $325 versus $250 for the FLEX option.

The practical and ISO exams must be completed in person regardless. There's no remote option for hands-on testing.

How St. Louis County Compares

These fees are specific to St. Louis County's IAPMO-administered exams. Other Missouri jurisdictions use different vendors at different price points. Jefferson City and Springfield use ICC exams through Pearson VUE; Springfield's research-listed exam fee is about $125. Kansas City uses Prometric or ICC exams. St. Charles County accepts ICC scores without pre-authorization and charges no county-level exam fee.

If you hold a valid journeyman or master exam score from another Missouri jurisdiction, St. Louis County evaluates reciprocity on a case-by-case basis — but there's no guarantee they'll accept an ICC score in lieu of their proprietary IAPMO exam.

Plan Your Testing Timeline

The Missouri Plumber License Guide includes the full IAPMO fee schedule alongside a jurisdiction comparison table so you can budget the total cost of licensing across St. Louis County and neighboring jurisdictions.

See more Missouri guides →