How to hire a plumber/pipefitter: skills, licenses, tests and interview questions

One bad pipe joint can sit behind a wall for years, then flood a floor or shut down a plant line. A plumber/pipefitter installs, maintains and repairs the piping that carries water, gas, steam, and process fluids through buildings and plants.

How to hire a plumber/pipefitter well comes down to three checks: match the work, verify the licenses and test hands-on skill. This guide gives you the steps, tests, and questions to do all three.

TLDR

• A plumber/pipefitter installs and repairs piping, and plumbers, pipefitters and steamfitters each work on different systems.
• A six-step process takes you from defining the work to onboarding.
• Check the licenses and certifications that match your type of work.
• Test hard and soft skills with an online test and a short practical task.
• Score candidates on a weighted scorecard and ask structured interview questions.
• Compare your offer against the latest US pay data before you post.

What does a plumber/pipefitter do?

A plumber/pipefitter lays out, installs, tests, and repairs piping systems and the equipment attached to them. Plumbers focus on water supply, drainage, gas, and fixtures, while pipefitters work on systems that carry chemicals, acids, gases, steam and high-pressure fluids in commercial and industrial settings, according to the US Bureau of Labor Statistics.

Day to day, a plumber/pipefitter on a commercial or industrial crew will usually:

• Read drawings: Work from blueprints, isometric drawings, and specifications to plan pipe runs, supports, and fittings.
• Measure, cut and join pipe: Thread, groove, solder, braze or weld copper, steel, stainless, PVC, CPVC and PEX, depending on the system.
• Install equipment: Set valves, pumps, backflow preventers, water heaters, boilers and process equipment.
• Test systems: Pressure test, hydro test, and leak test new work before it is covered or commissioned.
• Maintain and repair: Diagnose leaks, blockages, pressure drops, and failed components in live systems.
• Work safely and to code: Follow plumbing and mechanical codes, permits, inspections, and site safety rules.

What is the difference between a plumber and a pipefitter?

A plumber mainly works on water, drainage and gas systems in homes and commercial buildings, while a pipefitter builds and maintains piping for heating, cooling, steam and industrial processes, often at higher pressures and temperatures. Steamfitters are pipefitters who specialise in high-pressure liquid and gas systems.

Many people hold both skill sets, which is why job titles combine them. The difference matters for hiring because it changes the license you check, the test you run, and the people you source from.

Key takeaway: Write the job title around the work, not the trade name. "Commercial pipefitter, process piping, welding required" attracts a different and better-matched pool than "plumber/pipefitter wanted".

Why is it hard to hire a plumber/pipefitter right now?

Hiring a plumber/pipefitter is hard because demand keeps growing faster than new workers enter the trade. The BLS counts about 510,600 plumber, pipefitter and steamfitter jobs in 2025 and projects 7% growth from 2025 to 2035, with about 42,000 openings every year, many of them to replace workers who retire or leave the trade.

The wider construction market is just as tight. Associated Builders and Contractors estimated in January 2026 that the industry needs to attract 349,000 net new workers in 2026 and about 456,000 in 2027 to keep up with demand.

For hiring teams, that means three things:

1. Qualified candidates have options: A slow process loses them to the contractor down the road.
2. Resumes are thin: Many skilled fitters have short or no resumes, so screening on paper filters out good people.
3. Mis-hires are expensive: A failed weld, a skipped pressure test or a safety incident costs far more than a few extra hours of screening.

How to hire a plumber/pipefitter step by step?

The way to hire a plumber/pipefitter is to define the exact work first, then screen on credentials and tested skill before anyone spends time on interviews. The six steps below keep the process fast enough for a tight market and thorough enough for safety-critical work.

1. Define the work: List the systems, materials, joining methods, codes, and settings the person will handle. Residential service, commercial new build, industrial maintenance, and hospital work each need a different profile.
2. Write the job post: Name the license level, the joining methods, any welding or medical gas requirements, the shift pattern, and the pay range. Start from a plumber job description template and adapt it.
3. Screen credentials: Confirm license status with the state board, check welding qualifications and safety cards, and confirm apprenticeship or trade school completion.
4. Run a skills test: Send a short online knowledge test to everyone who passes the credential screen, then invite the top scorers to a practical task.
5. Score structured interviews: Ask every candidate the same questions and score answers on one scorecard, with safety as a pass-or-fail item.
6. Offer and onboard: Check references with a past foreman, move quickly on the offer, and plan the first week: site induction, safety briefing, and a buddy on the crew.

Pro tip: Put the pay range and shift pattern in the first two lines of the post. Tradespeople scan for those first, and many skip a post that hides them.

What licenses and certifications should you check?

The licenses and certifications to check depend on the work. Most states require plumbers to be licensed, usually after 2 to 5 years of experience and an exam, and some states also license pipefitters, steamfitters and gas line work, per the BLS guide on how to become a plumber or pipefitter.

Most candidates move through three levels:

• Apprentice. Learns on the job, usually through a 4 to 5 year apprenticeship with about 2,000 hours of paid training each year plus classroom instruction. Works under supervision.
• Journeyman (journey-level). Has completed an apprenticeship and passed a licensing exam. Can work without direct supervision.
• Master. Has more years of experience and a further exam. Can pull permits, supervise others and, in many states, run a contracting business.

Use this map to decide what to ask for:

Medical gas is the one most often missed. The ASSE 6010 medical gas installer certification is issued by NITC and renews every 3 years, after a 100-question written exam and a brazing exam.

Some states make it law. Minnesota requires a journeyworker or master plumber license, ASSE 6010, NFPA 99C brazing qualification and a current NITC card for medical gas work.

Always verify licenses directly with the issuing state board rather than relying on a photo or copy, and record the expiry date so you know when it needs renewing.

What hard skills should a plumber/pipefitter have?

A plumber/pipefitter needs strong technical skills in reading drawings, measuring and fitting pipe, joining methods, testing and code compliance. The exact mix depends on your systems, so rank these against the work you defined in step 1.

1. Blueprint and isometric reading: Turns drawings into an accurate cut list, including rolling offsets, slopes and elevations.
2. Measuring, cutting and fitting: Takes field measurements, calculates take-offs and fits pipe to tolerance the first time.
3. Joining methods: Threading, grooving, flanged joints, soldering, brazing, press fittings and, where needed, welding (see our guide on how to hire a welder for weld testing).
4. Materials knowledge: Knows when to use copper, carbon steel, stainless steel, cast iron, PVC, CPVC or PEX, and why.
5. Pressure and leak testing: Plans and runs hydrostatic and pneumatic tests, isolates sections, and documents results.
6. Codes and standards: Applies the local plumbing and mechanical codes and the piping codes your projects follow.
7. Troubleshooting: Diagnoses leaks, pressure loss, water hammer, failed valves, and blockages logically, from the simplest cause up.
8. Tools and equipment: Uses threaders, groovers, press tools, pipe benders, lasers, and lifting gear safely.
9. Mechanical reasoning: Understands how pumps, valves, pressure, and flow behave, which helps on HVAC and process systems.

What soft skills matter on a piping crew?

Soft skills matter because a plumber/pipefitter rarely works alone: crews share tight spaces, schedules and safety risks with other trades. The skills below separate a reliable crew member from a technically good but costly one.

• Safety discipline: Follows lockout, permit, and hot work rules even when a job is running late.
• Communication: Explains problems clearly to foremen, inspectors, facility staff and other trades.
• Teamwork: Coordinates with electricians, HVAC technicians, and general contractors on shared spaces and schedules.
• Attention to detail: Checks measurements, labels, supports, and test results before signing off.
• Problem-solving: Finds a safe workaround when the drawings do not match the site.
• Reliability: Turns up on time for early starts, shutdowns and call-outs.
• Adaptability: Handles changes to scope, shift patterns and site conditions without losing quality.

How do you test a plumber/pipefitter's skills?

The most reliable way to test a plumber/pipefitter is a two-part check: a short online knowledge test to screen everyone, then a practical task for the shortlist. The online test removes guesswork early, and the practical shows whether the knowledge carries over to real pipe.

Part 1: online knowledge test (15 to 30 minutes). Testlify's Plumber/Pipefitter test is a 15-minute, 15-question intermediate test covering plumbing system knowledge, pipe installation techniques, problem-solving, attention to detail and communication.

Pair it with a mechanical reasoning test for industrial roles or a safety awareness test for any site role.

Part 2: practical task (30 to 45 minutes). Keep it short, standard and scored the same way for everyone:

1. Isometric offset: Hand the candidate a simple isometric drawing and ask for the length of a rolling offset and the fittings needed. A journeyman should solve it quickly with a tape and a calculator.
2. Measure, cut and fit: Ask them to measure, cut and assemble a short run with two changes of direction to a set tolerance.
3. Joint identification: Show threaded, grooved, flanged, socket weld and butt weld joints and ask where each one is used.
4. Pressure test plan: Ask how they would test a new section: isolation points, test medium, pressure, hold time and what they record.
5. Fault scenario: Describe a pressure drop or hidden leak in a building they have never seen and ask how they would track it down without cutting into finished walls first.
6. Safety scenario: Ask what they do before working on a live steam, gas or hot water line.

If welding is part of the job, state the weld process and qualification you will test for in the job post and run the weld test separately to your written procedure.

Pro tip: Run the online test before the practical. Across the teams we work with, the practical is the most expensive step to run, so it should only go to candidates who have already shown the knowledge.

How should you score plumber/pipefitter candidates?

Score every plumber/pipefitter candidate on the same weighted scorecard so that a confident interview cannot hide their weak practical knowledge with charisma and confidence.

A scorecard only helps if every interviewer uses it the same way. Four habits keep the scores reliable and the hiring decision easy to defend:

1. Agree the weights first: Set them before the first candidate is scored, so nobody adjusts them to favour a person they like.
2. Score each row on its own: Rate knowledge, practical, safety, credentials and teamwork separately, then add up the total.
3. Treat safety as pass or fail: A strong total should never outweigh an unsafe answer or a missing license.
4. Write a reason for every score: One line citing what the candidate said or did helps the team compare notes and review the decision later.

Where can you find qualified plumber/pipefitters?

Qualified plumber/pipefitters are usually found through trade networks rather than general job boards alone. The best results come from mixing channels and from building your own pipeline of apprentices.

• Apprenticeship programs: Union and non-union apprenticeship programs, community colleges and trade schools. Sponsoring apprentices builds a pipeline you control.
• Union halls: For union shops, the local hall is the main route to journey-level fitters.
• Employee referrals: Fitters know other good fitters. A referral bonus paid after 90 days rewards hires who stay.
• Trade associations and events: Local contractor associations, trade shows and skills competitions.
• Job boards: General and trade-specific boards, with the license, pay range and shift pattern in the title or first line.
• Related trades: HVAC technicians, welders and maintenance mechanics often move into pipefitting. Our HVAC technician hiring guide covers that adjacent pool.
• Military transition programs: Veterans with utilities, plumbing or pipefitting experience.

What should a plumber/pipefitter job description include?

A plumber/pipefitter job description should state the work setting, systems, license level, joining methods, certifications, schedule and pay so the right people apply and the wrong ones self-select out. Use this template and fill in the brackets.

Job title: [Commercial / Industrial / Service] Plumber/Pipefitter, [Journeyman / Apprentice / Master]

About us: [Company name] is a [industry] company in [location]. We [one line on the projects or facilities the person will work on].

What you will do:

• Install, maintain, and repair [water, drain, gas, steam, chilled water, process] piping systems in [setting].
• Read blueprints and isometric drawings to plan and fit pipe runs.
• Join pipe by [threading, grooving, press, brazing, welding].
• Pressure test and document new and repaired systems.
• Work to [local plumbing code, mechanical code, ASME B31 code] and site safety rules.
• Coordinate with foremen, other trades and facility staff.

What you need:

• [Journeyman/master] [plumbing/pipefitting] license in [state], or completion of a registered apprenticeship.
• [X]+ years of experience in [commercial/industrial / healthcare] piping.
• [Welder qualification for process and position] (if applicable).
• [ASSE 6010 medical gas certification] (if applicable).
• OSHA 10 or OSHA 30 card, or willingness to obtain one.
• Valid driver's license and own hand tools (if applicable).

Pay and schedule: $[X] to $[Y] per hour, [shift pattern], [overtime and call-out terms].

Benefits: [health cover, retirement plan, paid time off, tool allowance, training and license renewal support].

How to apply: [Apply link]. Shortlisted candidates complete a 15-minute online skills test, then a short practical.

What interview questions should you ask a plumber/pipefitter?

The best interview questions for a plumber/pipefitter ask for specific past jobs and real procedures, not opinions. Ask every candidate the same questions and score each answer against what a strong answer contains.

Technical questions

1. Walk me through how you would fit a rolling offset from an isometric drawing. What measurements do you need?
2. Which joining methods have you used most, and on which materials and systems?
3. How do you plan and run a pressure test on a new section? What do you record?
4. Tell me about a leak or pressure problem you traced in a building you did not know. How did you find it?
5. Which codes do you work to most often, and how do you keep up with changes?

Safety questions

1. What do you check before opening a line that may be live with steam, gas or hot water?
2. Describe a time you stopped work because something was unsafe. What happened next?
3. What does a hot work permit or confined space entry involve on your sites?

Teamwork and communication questions

1. Tell me about a time the drawings did not match the site. How did you handle it with the foreman or engineer?
2. How do you coordinate with electricians or HVAC crews working in the same space?
3. How would you explain a costly repair to a facility manager who wants it done cheaply?

Experience and fit questions

1. What is the largest or most complex system you have worked on, and what was your part?
2. Which licenses and certifications do you hold, and when do they expire?
3. Are you comfortable with [shift pattern, travel, call-outs]?
4. What would you want to learn or certify in next?

Strong answers name materials, pressures, tools, codes and the order of steps. Weak answers stay general ("I always follow the code") without a real example.

How much does a plumber/pipefitter cost to hire?

A plumber/pipefitter in the US earns a median of $63,800 a year, or $30.67 an hour, according to BLS data for May 2025. The bottom 10% earned less than $44,150 and the top 10% more than $108,420, with pay rising for licensed, welding-certified and industrial specialists.

Pay varies widely by state, union status, industry, and overtime. Check local rates before you post, and budget beyond wages for tools, safety gear, license renewals, training, and overtime on shutdowns or call-outs.

How can Testlify help you hire plumber/pipefitters?

Testlify helps you hire plumber/pipefitters by testing real skills before the interview, so your foremen spend their time only on candidates who can do the work. Teams use it to screen trade roles at volume without lowering the bar.

• Testlify offers the Plumber/Pipefitter test and related tests such as plumber, welding, mechanical reasoning and safety awareness from a library of 3,500+ tests.
• You can add your own role=specific scenario questions using 25+ question types, including video answers where a candidate explains a procedure.
• 20+ proctoring checks help keep online test scores trustworthy, as explained in our page on anti-cheating and proctoring.
• Testlify connects with 100+ ATS and HRIS integrations and runs tests in 15+ languages for multilingual crews.
• Automated scoring ranks candidates so you know who to invite to the final interview.

If you hire across several trades, our guide to pre-hire assessments for the construction industry shows how to set up one process for all of them.

Ready to test plumber/pipefitter skills before the interview? Book a demo to see the Plumber/Pipefitter test in action.

Frequently asked questions (FAQs)