Mississippi Plumbing

Mississippi Plumbing Exam: What to Know Before You Walk In

You've put in the work on the job. Now you need the Mississippi Plumbing License to prove it. The state's contractor plumbing exam is 70 questions, open-book, and covers everything from drain sizing to isometric drawings to OSHA confined space requirements. It's not a casual test, but it's very passable with the right prep. This article breaks down exactly what's on the exam, what to study, and how to get ready — including some sample Mississippi plumbing exam questions to show you what you're walking into.

Want to test yourself right now? Take our free practice exam and see where you stand.

Mississippi Plumbing Exam Overview

The exam covers unlimited commercial and residential plumbing — not fuel gas, not boilers. Here's the basic structure:

• Questions: 70 scored questions
• Time limit: 180 minutes (3 hours)
• Passing score: 70% — you need 49 correct answers out of 70
• Format: Multiple choice, computer-delivered at a PSI testing center
• Open book: Yes — you bring your own references (more on that below)

The exam is administered by PSI. Once the Mississippi State Board of Contractors approves your application, PSI will email you a confirmation. You can then register through the exam registration page anytime — it's available 24 hours a day — or call PSI at (855) 557-0619 during business hours. Check the official exam bulletin for current testing locations and any updated requirements.

Your score appears on screen immediately after you finish. Pass, and you get a performance summary. Don't pass, and you get a diagnostic report breaking down your results by topic area — useful for knowing what to hit harder on the next attempt.

What Topics Are on the Exam

The exam is built around the International Plumbing Code (2021) and OSHA 29 CFR Part 1926, plus pipe math. Here's how the 70 questions are distributed across topics:

Drain, Waste, and Vent is the biggest section by far — 15 questions. Know your DFU values, drainage pipe sizing, slope requirements, and vent types cold. Isometric Analysis is second at 12 questions; that's pipe math from drawings. Together those two sections are 27 of your 70 questions. If you lose both, you almost certainly fail. Focus there first.

Sample Mississippi Plumbing Exam Questions

Here's a look at the style and difficulty of actual exam questions. Work through them — answers not included, on purpose.

Question 1 — Water Supply
Under the International Plumbing Code, when a limiting device is used to control tempered water temperature, what is the maximum temperature to which it must be set?

• A) 120°F
• B) 110°F
• C) 140°F
• D) 100°F

Question 2 — Joints and Connections
When installing PVC plastic pipe solvent-cement joints in a sanitary drainage system, under what condition may the purple primer be omitted?

• A) When the solvent cement is third-party certified to ASTM D2564 and used only for DWV pipe 4 inches or smaller in nonpressure applications
• B) When the solvent cement is orange in color and conforms to ASTM F493
• C) When the pipe is installed below ground and the ambient temperature exceeds 40°F
• D) When the installer has verified that joint surfaces are clean and free from moisture

Question 3 — Water Supply
Shutoff valves are required on the water supply pipe to each sillcock.
(True/False — know your IPC cold for this one.)

Question 4 — Joints and Connections
Heat-fusion joints for polypropylene (PP) plastic pipe in a water supply system must be made in accordance with which standard?

• A) ASTM F2389
• B) ASTM F1412
• C) ASTM D2657
• D) ASTM F1673

Question 5 — Safety (OSHA)
Under OSHA construction regulations, if an employer fails to provide required PPE to individual employees, how may each failure be treated?

• A) As a separate violation with respect to each employee not provided with the required PPE
• B) As a single violation regardless of how many employees were affected
• C) As a minor infraction subject only to a written warning for the first occurrence
• D) As a recordable incident only if a workplace injury result

Not sure on any of these? Take our free practice exam and check your instincts against 10 real-style questions.

What Types of Questions to Expect

Our full practice exam bank has 500 questions across all 14 topics. Here's what each topic actually tests:

• Drain, Waste, and Vent: DFU calculations, horizontal and vertical drain sizing, slope requirements, and vent types — individual, common, wet, circuit, and air admittance valves. This is the meat of the exam.
• Isometric Analysis: Reading isometric drawings and calculating center-to-center and end-to-end pipe lengths, 45-degree offset math, and three-pipe offset diagrams.
• Cleanouts: Placement intervals, directional change requirements, size rules, clearances, and access requirements.
• General Plumbing Regulations: Installation requirements, material standards and certifications, pipe protection from freezing and corrosion, trenching and backfill, and required tests and inspections.
• Fixtures and Equipment: Minimum fixture counts by occupancy, material standards, installation clearances, water closet and urinal rules, and shower compartment construction.
• Traps and Interceptors: Trap seal depths, prohibited trap types, distance limitations, grease interceptor sizing, and oil separator requirements.
• Water Supply: Backflow prevention, pipe material and sizing, cross-connection protection, and hot water system requirements.
• Safety: Confined space classification and permit requirements, atmospheric testing, roles of supervisors and attendants, rescue procedures, and employer PPE responsibilities under OSHA 1926.
• Piping, Valves, Controls: Approved pipe materials by application, joint methods by material type, valve placement, and backflow prevention device selection.
• Joints and Connections: Solvent cementing, solder, brazed, press-connect, push-fit, and caulked joints — plus transitions between different piping materials.
• Developed Length: Center-to-center vs. end-to-end measurements, fitting allowance math, diagonal and offset calculations, and vent piping length for sizing.
• Backflow: Definitions, hazard-level device selection from Table 608.1, device types and standards, and installation requirements.
• Water Heaters: T&P relief valve installation, discharge piping specs, access clearances, antisiphon and vacuum relief devices, and pan drain requirements.
• Hangers and Supports: Horizontal and vertical support intervals by material type per Table 308.5, hanger material rules, sway bracing, and anchorage at direction changes.

Study Materials

This is an open-book exam, so what you bring matters. Here's what's allowed:

Required references:

• International Plumbing Code 2021 — the main code book for the bulk of the exam
• OSHA Standards for the Construction Industry — 29 CFR 1926 — covers the Safety section
• Mathematics for Plumbers and Pipefitters by Lee Smith, 8th Edition, 2013 — covers the math sections (Developed Length, Isometric Analysis)

Books may be highlighted or indexed with permanent tabs. They cannot have loose papers tucked inside or written notes beyond highlighting and underlining.

Make the most of your references:

Tab and highlight heavily before exam day. If you have to flip through the entire IPC to find a DFU table mid-exam, you're burning time. Use Redi-Tag Permanent White Tabs to build a clean index — tables, code sections, key definitions. They hold tight and are laser-printable so your labels stay readable.

For highlighting, Sharpie Tank Highlighters are a solid choice — bright fluorescent ink, chisel tip that works for both underlining and marking, and a large ink supply that won't dry out mid-book. Use different colors for different topics.

For serious exam prep beyond the books, use the full practice exam at our site. It mirrors the real exam: 70 questions, 180-minute timer, same topic breakdown. Every attempt pulls from a large question pool so you don't see the same test twice.

Study Tips That Actually Help

On tough questions, eliminate first. Rule out the options you know are wrong before you choose. Getting down to two options improves your odds significantly, even when you're unsure of the right answer.

Use your time — all of it. You have 3 hours for 70 questions. That's well over 2.5 minutes per question. Don't rush. Other people finishing early means nothing. Work through each question steadily and go back to review before you submit.

Trust your first instinct, but correct it when you have a real reason. If you misread a question or a later question reminded you of something, change the answer. What you want to avoid is changing answers purely because you're nervous. Considered changes help more often than they hurt.

Tab your code book before exam day, not during. There's no time to hunt for tables at the test center. Know exactly where Table 308.5 is, where the DFU table is, where the backflow device table is.

Do the math sections by hand first. Isometric analysis and developed length questions require arithmetic. Practice with a silent, non-programmable, battery-operated calculator — that's all you're allowed to bring.

Start Prepping Now

The Mississippi Plumbing exam is passable. Seventy questions, open book, 3 hours — the structure is on your side. What beats most people is showing up underprepared on the math sections and not knowing where to find answers in the code book fast enough.

Fix both of those and you're in good shape. Start with our free practice exam — 10 questions, no account needed — and see where you actually stand. When you're ready to go deeper, the full practice exam mirrors the real test with 70 questions, a 180-minute timer, and a per-topic score breakdown so you know exactly what to hit harder.

Get your books tabbed, do your practice questions, and go pass it.