How to Screen Plumbers: 8 Questions and What to Listen For Screening Interview Template

What is your current plumbing license level (apprentice, journeyman, master), which state issued it, how many documented hours or years do you have toward the next level, and are you able to pull permits under it?

What this assesses: License level sets legal scope and decides whether the candidate can work unsupervised or pull a permit, so it gates everything else. Strong answers name the level, issuing state, license number, and roughly how many hours they have logged, and are clear about whether they can permit; be cautious with a candidate who calls themselves a journeyman but cannot name the issuing state or produce a number, or who assumes a license from another state transfers without a reciprocity check.

Is your background mostly service and repair, new construction, or remodel? Walk me through a typical day in your last role, including how many calls or how much footage you handled.

What this assesses: Service and new construction are close to different jobs, and mismatching them is the most common reason a technically solid plumber washes out in the first month. Strong answers describe the work concretely, six to ten service calls a day or a specific rough-in scope, and know which side they are better at; be cautious with a candidate who claims equal strength in both with no detail, which usually means light exposure to each.

Describe the last drain or sewer problem you diagnosed that was not what the customer described. How did you find the actual cause and what did it take to fix it?

What this assesses: Diagnosis is the difference between a plumber and a parts changer, and this question is hard to fake. Strong answers walk a real sequence, what they ruled out, whether they ran a camera or a locator, what the root cause turned out to be, and what the repair involved; be cautious with a story that jumps straight to a fix with no diagnostic steps, or a generic answer about how they always check everything.

What systems and materials have you worked with: PEX, copper, cast iron, PVC and ABS, gas lines, tankless and standard water heaters, backflow devices, sewer camera and jetting equipment? Where are you strongest and where would you need support?

What this assesses: Maps actual capability to the work you sell and exposes gaps before a dispatcher sends them on a call they cannot finish. Strong answers rank themselves honestly, name specific brands or joining methods, and admit one or two areas they would want a ride-along on, gas and backflow being common ones since both often carry separate certification; be cautious with a candidate who claims every system and every brand, since that is rarely true and predicts callbacks.

Tell me about a time an inspector failed your work or a job you completed came back as a callback. What was wrong and what did you change afterward?

What this assesses: Every working plumber has failed an inspection, so a denial here is a bigger flag than an admission. Strong answers name the specific code issue, venting, slope, improper support, missing cleanout, and describe the correction plus what they do differently now; be cautious with a candidate who says it has never happened, or who blames the inspector without ever describing what the code actually required.

Most of this work happens in someone's home. Describe how you explain a repair and its price to a customer who is upset about the cost, and tell me about a time a customer refused the work you recommended.

What this assesses: In service plumbing the customer conversation drives the ticket and the review score, and skill here is uneven even among strong technicians. Strong answers describe explaining the problem in plain language, showing the customer what they found, giving options at different price points, and documenting a declined repair without pressure; be cautious with a plumber who is dismissive of homeowners, leans on hard-sell language, or has never had to quote a price at all, which usually means a new-construction background.

What tools do you own, do you have a truck you would use for work, and do you hold a valid driver's license with a clean enough record to be insured on a company vehicle?

What this assesses: Tool ownership and a clean driving record are practical dealbreakers, and companies split on who supplies the truck and the stock. Strong answers list a real hand and power tool inventory, may name diagnostic equipment they own such as a camera or a locator, and answer the driving record question directly; be cautious with a candidate who owns almost nothing, or who is vague about a suspension or recent violations that will keep them off your insurance policy.

What is your on-call and overtime availability, including nights, weekends, and emergency rotations? Do you have a drug screen and background check concern we should know about, and how soon could you start?

What this assesses: On-call rotation is where plumbing hires quit, so surface it before the offer rather than after. Strong answers give a specific rotation they can work, one week in four or every other weekend, accept that emergency calls come at bad hours, consent to screening, and give a realistic start date that accounts for a notice period; be cautious with a blanket 'whatever you need' that collapses the first time a Saturday night sewer backup lands, or hesitation on a routine drug screen most service companies require. Pair this template with [structured interview](/glossary/structured-interview) scoring so on-call fit is weighted the same for every candidate, and see the [skilled trades hiring guide](/for/skilled-trades-hiring) and the [HVAC technician template](/templates/hvac-technician) if you are staffing a full mechanical crew.