Plumbing Study Guide 2026
Everything you need to pass the Plumbing exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 Plumbing Exam Format at a Glance
📚 Plumbing Topics to Study (21)
✍️ Sample Plumbing Questions & Answers
1. Which fitting should be used when connecting a horizontal drain line to another horizontal drain line at the same elevation?
A 45-degree wye fitting is used to connect horizontal drain branches because it promotes laminar flow and reduces the chance of blockages.
2. What is the safe, approved method for detecting a gas leak at a fitting or connection?
Applying an approved leak detection solution or soapy water to fittings and observing for bubbles is the safe standard method — open flames are extremely dangerous.
3. What does the term 'authority having jurisdiction' (AHJ) mean in plumbing codes?
The AHJ is the local organization, office, or individual responsible for enforcing the requirements of the applicable plumbing code in that jurisdiction.
4. What is required before starting a major plumbing project in most US jurisdictions?
Most major plumbing work requires a permit from the local authority having jurisdiction (AHJ), ensuring the work is inspected and meets code requirements.
5. What is the minimum water pressure required at a residential fixture per the IPC?
The IPC requires a minimum static water pressure of 20 psi at every plumbing fixture to ensure adequate flow for proper operation.
6. What is the maximum distance a lavatory trap can be from its vent?
Under the IPC, a lavatory (sink) with a 1.25-inch pipe has a maximum trap-to-vent distance of 3.5 feet, but the common code limit for lavatories is 5 feet depending on jurisdiction — 4 feet is the most commonly tested standard answer.