Ask whether the plumber is ROC-licensed and for the license number and classification, for current liability and workers' comp certificates, for a written itemized estimate, who pulls permits, the labor and parts warranty, how pricing works, who does the work, cleanup terms, and payment terms.
Are you ROC-licensed, and what is your number and classification?
Ask this first. In Arizona, plumbers are licensed by the Registrar of Contractors (ROC), and a license number lets you confirm everything else they tell you. Get the number, then check it yourself at the free public ROC license search at roc.az.gov/search. Confirm the license is Active, that the classification matches the work, and that there is no troubling complaint history.
Classification matters because it defines what the contractor is allowed to do. Common plumbing classes are C-37 (commercial plumbing), R-37 (residential plumbing), and CR-37 (dual). Sewer, drain, and pipe-laying work that runs into easements or the public right-of-way falls under the separate A-12 classification. A plumber holding the right class for your job is one quick check that screens out a lot of risk.
There is real money behind a license too. Arizona's Residential Contractors' Recovery Fund, under A.R.S. 32-1132, can reimburse a homeowner up to $30,000 for damage caused by a licensed residential contractor whose license is suspended or revoked over a complaint. Hire someone unlicensed and you give up that protection entirely. That is the difference a license number makes.
Can I see current proof of insurance?
Ask for current certificates of both general liability and workers' compensation insurance, and read the dates. Liability covers damage the plumber does to your home. Workers' comp covers their crew if someone is hurt on your property, which keeps that bill off you.
This is not a formality, and the FTC is blunt about why. Its guidance states: "Ask to see a copy of the contractor's insurance certificates to confirm they have coverage, and that it is current. If they don't, you could be held liable for accidents that occur on your property." Read that twice. A lapsed policy or a missing workers' comp line can land an injury claim on your homeowner's policy. A real plumber carries the coverage and will show you the paperwork without flinching.
A current certificate also confirms the business is operating as a business, not a side hustle working off the books. Pair the insurance check with the license check from the question above and you have screened out most of the contractors who cause the worst horror stories.
Will I get a written, itemized estimate, and how is the price set?
Insist on a written estimate before any work starts, and make sure it is itemized. The FTC tells homeowners a written estimate should list the work to be done, the materials, the completion date, and the price. A number scrawled on the back of a card is not an estimate. An itemized written estimate is what you compare against the final bill if there is ever a dispute.
While you have them on the phone, settle how the price is built:
- Flat-rate or hourly? Flat-rate quotes a set price per job, so you know the cost up front. Hourly (time-and-materials) bills for the actual time and parts. Neither is wrong, but you should know which one you are agreeing to.
- Is there a trip or diagnostic fee? Many shops charge to show up or to diagnose. Ask whether that fee applies, how much it is, and whether it rolls into the job if you hire them.
- Are permit fees passed through? Permit costs are a legitimate pass-through. Ask to see them on the estimate rather than buried in a single lump number.
Get more than one written quote, and do not reflexively pick the lowest. A bid far under the others often means missing insurance, no permits, or corners that cost you later.
Do you pull permits, who does the work, and what is the warranty?
These three questions separate a real contractor from a fly-by-night crew.
Do you pull the required permits? For repipes, water heater changeouts, gas piping, sewer and water service lines, and added or relocated fixtures, Phoenix generally requires a permit, and a licensed contractor should pull it. A plumber who pushes you to skip the permit is asking you to own the code-compliance risk on hidden work. Let them pull it.
Who actually does the work? Ask whether the people on your job are employees or subcontractors. If subs do the work, ask whether each sub is licensed and insured to the same standard. The protections above only hold if the person turning the wrench is covered.
What is the warranty on labor and parts? Get it in writing and read the terms. Parts often carry a manufacturer warranty, while labor is the contractor's own promise. Know how long each lasts and what voids it before you sign.
Do you clean up and haul the old equipment? Confirm that removal of the old water heater, fixture, or pipe and general cleanup are included, so a haul-away charge does not surprise you at the end.
What are the payment terms, and what are the red flags?
How a plumber wants to be paid is one of the loudest signals you get. The FTC's rules for homeowners are direct: "Don't pay with cash. Don't pay the full amount up front. And don't make the final payment until the work is done and you're satisfied." Hold to that and you keep the upper hand until the job is right.
A reasonable structure is a modest deposit, with the balance due on completion and inspection. Holding the final payment until you are satisfied keeps the pressure on the plumber to finish the job correctly, not on you to chase a contractor who already cashed your check. It also gives you a simple way to enforce the warranty: if a problem shows up during the walkthrough, it gets fixed before the last dollar changes hands. Watch for these warning signs, which the FTC flags as scam patterns:
- Pressure to decide immediately or sign on the spot.
- A demand for cash only or payment in full before work begins.
- A "great deal" using leftover materials from another job, often pitched door to door.
- No written contract, no license number offered, or no willingness to show insurance.
None of these questions takes long, and a trustworthy plumber answers them all without hesitation. The ones who stall, deflect, or push back are screening themselves out for you.
If you want to go deeper on any single step, see our guides on how to choose a plumber, how to verify a plumber's ROC license in Arizona, and why a licensed, bonded, and insured plumber matters. Run the full list every time, keep the written estimate, and you will rarely get burned hiring in Phoenix.