What skills tests should you give HVAC and plumbing candidates?

Let the job ad write the test.

If the posting names a rung on your ladder, the practical test samples the work that rung does in its first month on your trucks — not the whole trade.

Pitch the test at the rung you are hiring for: a test pitched above it asks the candidate to work ahead of the role, and one pitched below it may not separate two candidates who both clear it.

If your shop has not written its ladder yet, our guide to HVAC technician levels shows how one is built — our research found no industry-standard level system to copy, so the rungs are yours to define.

Helper and apprentice rungs.

Build small stations out of ordinary shop work: identify common components on a retired unit — a capacitor, a contactor, a blower motor — and say what each does in the system; take a continuity reading on an unpowered board and write down what the meter says; make one copper joint on practice stock and talk through the steps while working.

The plumber practical test at this level is the same idea with pipe: measuring, cutting and dry-fitting practice stock, and labeling a section of drain, waste and vent line you have assembled for the bench.

What you are scoring at this rung is not mastery.

It is whether the hands are careful, the measurement gets checked twice, and the candidate asks before guessing.

Service-tech rung.

Hand them a diagnosis instead of a task.

Give the candidate the wiring diagram from a unit you own, an unpowered board with one fault you staged, and a meter, and watch four things: whether they find the diagram's legend before touching anything, whether they trace the control circuit in order, whether the failed part they name is the one you staged, and whether they can say why out loud.

Add a charging judgment as a scenario — printed gauge readings, a target subcooling figure, and one question: what do you check first?

Listen for whether the candidate reasons from the readings or guesses from memory.

Lead and senior rungs.

Make the stations messier on purpose: two faults at once, no service history, a customer waiting.

Then flip the exercise from finding a fault to planning a job — scope the visit, list the parts, sequence the day, and explain the fix back to you as if you were the customer.

At this rung the test weighs judgment and communication as heavily as wrench time, because the exercises you are setting — planning a job, explaining a fix — are judgment and communication.

One station carries a credential question with it: anything that opens the refrigerant circuit.

Keep the circuit sealed on the test bench and score refrigerant-side judgment with gauges and scenarios instead; when a hire will handle refrigerant on real calls, verify their EPA 608 certification as part of your credential screen — our guide to verifying a tech's EPA 608 certification covers that check.

Build the bench test out of the jobs you dispatch every week, not out of a puzzle book.

Pick the work your crew does most, strip each job down to what one person can show you at a bench, and write a station card for each: what the candidate gets (the diagram, the meter, the practice stock), what they must produce (a reading, a named part, a joint that holds), and where the clock stops.

The bench itself stays humble — a retired air handler, a meter from the truck, a roll of wire and the floor plan of a job you finished last month are enough.

What makes a test real is that the fault you staged is one your techs actually found on a Tuesday, not a riddle built to stump people.

The wiring test specifically: tape the unit's own diagram to the bench rather than a generic schematic, and on the unpowered board stage the fault by leaving one low-voltage wire off its terminal.

Score it in four lines — found the legend, traced the circuit in order, named the staged part, explained why.

A candidate who goes straight to parts-swapping without reading the diagram has shown you something an interview answer might not.

The plumbing bench works the same way with pipe.

Assemble a section of drain, waste and vent line on practice stock with one defect in it — a fitting installed backward, a run without the fall it needs — and ask the candidate to find it and mark the correction on paper before touching anything.

Pair it with a floor-plan exercise: hand over the plan of a bathroom you have actually built and ask for the rough-in locations and the venting logic.

You are listening for whether the candidate thinks in the system or only in the pipe.

Then write the instructions down and set the clock.

The same instructions sheet, the same stations and the same clock for every candidate at a level — improvising the test fresh for each person is how scores stop meaning anything, and the next section asks about the same consistency from the legal side.

Keep the test contained, too: the moment a "test" becomes an hour of real, productive work for you, it has stopped being an assessment and started being a try-out day — a different activity with its own pay and insurance questions.

That is the working interview, and the last section below covers where it fits in the sequence.

Write the scorecard before the first candidate sits down, and write it in outcomes you can see.

Per station: what a pass looks like ("the failed part is the staged part," "the reading is taken and written down," "the joint holds"), a simple scale, and a notes line for method.

Score method as well as outcome — the candidate who takes a wrong reading and writes down what the meter actually said is showing you something about honesty that a number alone hides.

Consistency is the whole game.

Same stations, same instructions sheet, same clock, same scorer role, for every candidate at the same level.

Score on the sheet during the station rather than from memory at the end of the day, sign it, date it, and keep it with the candidate's file.

The sheets earn their keep twice: they are how you compare two candidates on something better than a gut feel, and they are the record of how each decision was made if anyone ever asks.

The legal rule to know comes from the Uniform Guidelines on Employee Selection Procedures (29 CFR part 1607): under those guidelines, a hiring test that has adverse impact on a race, sex or ethnic group is treated as discriminatory unless the test has been validated.

Two habits follow for a shop — our practical reading of the guidelines rather than legal advice.

First, keep the test job-related by construction — stations sampled from the work you actually dispatch, which is what this page has you build.

Second, apply it the same way to everyone and keep the sheets.

Neither of those makes a test "validated" — validation is its own exercise, our research did not cover how shops validate a selection test, and whether yours needs it is a question to put to an employment attorney before you use scores to turn candidates away.

One state changes what your file is worth after the hire.

Montana is the exception to at-will employment: once a hire has completed the employer's probationary period, discharge without good cause is wrongful under Montana's Wrongful Discharge from Employment Act.

In Montana, during the probationary period itself, either side may end the employment for any reason or none.

If you hire in Montana, keep the dated test sheets and the notes from the probationary period the way you keep invoices — they are your record of how each decision was made.

Probationary periods are their own topic with their own rules; this page stays on the testing decision that happens before any offer.

Run both, in that order, because they measure different things.

The written test is cheap to run, identical for every candidate, and good at what a bench cannot show in a few minutes: whether a candidate can reason through a fault they have not personally seen, sequence a job, and explain a fix in plain words.

The hands-on bench is where the resume meets reality — tool habits, how they treat a meter, whether the hands match the claims.

A written test alone can pass someone who has never held a gauge; a bench alone can pass someone who cannot tell you why the fix works.

So sequence them.

A short written page of scenarios — what do you check first, what does this reading tell you, what do you tell the customer — thins the pile before you spend bench time on anyone.

The bench goes to the shortlist.

The finalists prove it on the truck in a working interview — a try-out day you schedule as paid time, and the pay and insurance setup is what our guide to working interviews for HVAC and plumbing candidates covers.

Each step tests something the one before it could not, and by the time you make an offer you have a signed sheet for the work the role actually does.

A low score is placement information before it is a rejection.

The helper-level candidate who fumbles the meter but reads the diagram carefully may be a strong hire at the helper rung with a training plan behind it, while a polished bench performance with no explanation behind it warns you about the customer's doorstep.

Score the sheet, decide which rung the result supports, and record the reason either way — the same discipline that made the test fair is what makes the decision useful.

And keep the test in proportion: it is one screen in a stack, and sourcing, offers and onboarding are the rest — our guide to hiring HVAC and plumbing techs is the whole picture.

This page is employer career and business information, not legal advice. The hiring-test rule summarized here comes from the Uniform Guidelines on Employee Selection Procedures, and Montana's rule from its Wrongful Discharge from Employment Act — selection testing, at-will employment and probationary periods are legal questions, so confirm how they apply to your shop with an employment attorney before you use a test score to turn anyone away.