12 Questions to Ask a Plumber Before Hiring (and the Red Flags in Their Answers)
Most homeowners interview a plumber the way they interview a contractor — by asking about price and timeline. That's two of the right questions, missing about ten more that actually predict whether the work will be done right. Here are the 12 questions to ask before you sign anything, what good answers look like, and what specific words should make you walk away.
1. May I have your license number?
A licensed plumber recites this from memory or pulls out their card. They are not offended by the question. Bad answer: 'My boss handles that' or 'You don't need to worry about it.' If they refuse to give the number, the conversation should end. Verify the number on your state's contractor licensing board website before scheduling.
2. Can you provide a certificate of insurance and bond proof?
Good answer: 'I'll email it before the appointment' or 'Here, scan this QR code on my truck.' Bad answer: any version of 'we're covered, you don't need to see paperwork.' A legitimate plumber's liability insurance is at least $500,000 and they can email proof within an hour.
3. Will you pull a permit for this job?
Most jurisdictions require permits for water heater replacement, gas line work, repiping, sewer line repair, and any new fixture install. Good answer: 'Yes, the permit is $X and included in the quote.' Bad answer: 'Permits aren't really needed for this' or 'You can save $200 if we skip the permit.' Skipping permits creates an insurance and resale problem that you will own.
4. Is this a flat fee or hourly, and what's included?
Good answer: a specific dollar figure or hourly rate, plus a clear list of what's included (labor, basic parts, disposal, warranty) and what's extra (specialty parts, code upgrades, permits). Bad answer: vague 'shouldn't be more than $X' without itemization.
5. What's your warranty on labor?
Industry standard for residential plumbing labor warranty is 1 year on most work, 2-5 years on water heater installs, 5-25 years on repipes (matching the pipe manufacturer's warranty). Good answer: a specific term and what voids it. Bad answer: 'We stand behind our work' with no specifics.
6. Who exactly will be doing the work?
Sometimes the licensed plumber sells the job and an apprentice does the work. That's legal in most states as long as a licensed plumber supervises and pulls the permit. Good answer: 'Our journeyman Mike does the install and I inspect before sign-off.' Bad answer: 'Someone from the team will be there' with no specifics.
7. What's your timeline?
Good answer: a specific date and time window, with realistic disclosure of weather, parts, or permit dependencies. Bad answer: 'next week, probably Thursday' with no follow-up. Plumbers who can't commit to a timeline often can't commit to other things either.
8. What parts and brand are you using?
Good answer: a specific brand and model number. Bad answer: 'whatever's available' or 'standard parts.' For water heaters, faucets, valves, and pressure regulators, the brand and model matter — they determine longevity and warranty. Ask for the model in writing.
9. Can you give me references from work in this neighborhood?
Good answer: 'Sure, here are three from this ZIP code, all installed in the last year.' Bad answer: 'My website has reviews' without specific local references. References from your neighborhood are higher signal than online reviews because the work is local, recent, and verifiable.
10. What happens if the scope grows mid-job?
Sometimes a plumber opens a wall and finds rotted subfloor, corroded valves, or a code violation that needs fixing. Good answer: 'I stop work, call you, and email a written change-order quote before continuing.' Bad answer: 'I'll handle it and add it to the bill.' The second answer is how $1,500 jobs become $4,500 jobs.
11. How do I pay you, and when?
Industry-standard payment for residential work: 25-50% deposit on large jobs, balance on completion. Good answer: a written payment schedule with milestones for big jobs. Bad answer: 'Cash up front' or 'I need the whole thing before I start.' Pay attention to payment methods — credit card provides chargeback protection that cash does not.
12. What's your name?
This sounds obvious, but ask for the name of the actual person showing up and the name of the licensed plumber responsible. Some plumbing companies operate under several DBAs, and you want to know who you're hiring on paper. Good answer: a clear name, business legal name, and license-holder name. Bad answer: only a business name with no individual.
You won't ask all 12 of these every time. For a $200 service call, three or four will do. For a $5,000 water heater install or a $15,000 repipe, ask all 12 — the 20 minutes you spend on this interview will save you days of frustration if the answers reveal someone who shouldn't have your business.