Arizona plumbing contractors are licensed through the Arizona Registrar of Contractors. Getting one generally requires several years of documented trade experience plus passing both a trade exam and a business exam. It is not a formality.

Go to azroc.gov and search by company name or license number. You will see whether the license is active, what classification it covers, how long it has been held, and any complaint history. It is free and it takes longer to read the results than to run the search.

Ask for the license number when you call, before booking. A licensed company will give it to you without hesitating, and most print it on the estimate. If someone will not give you a number over the phone, that answers your question.

While you are checking, confirm they carry liability insurance and workers’ compensation. If an uninsured worker is hurt in your house, that can become your problem.

1. No written estimate before work begins. Verbal ballparks have a way of growing once the wall is open.
2. Pressure to decide immediately. Real emergencies exist. But “this price is only good today” on a non-urgent repair is a sales tactic, not a plumbing assessment.
3. Cash-only, or a discount for paying cash. Sometimes it is a small operator avoiding card fees. Sometimes it means no paper trail, no warranty, and no recourse.
4. A large deposit up front. For a standard repair there is rarely a reason to pay much before work is done. Large material orders for a repipe are a different situation, and even then it should be documented.
5. They will not show you the problem. A plumber who is confident in the diagnosis will point at it. Photos, a camera feed, the corroded part in their hand. Being told a thing is broken without seeing it is a fair reason to get a second opinion.
6. The estimate jumps dramatically once they are inside. Some scope changes are legitimate and get discovered on site. What is not legitimate is a quote structured low to get in the door.
7. Vague or missing warranty terms. Ask what is covered, parts or labor or both, and for how long. If the answer is “we stand behind our work,” ask them to write down what that means.

Four questions cover almost everything that matters.

What is your ROC license number? Verify it yourself.

Will I have the price in writing before any work starts? The answer should be an immediate yes.

What is the warranty, on parts and on labor, and how long? Specific numbers, not reassurance.

If this turns out to be bigger once you open it up, what happens to the quote? This is the question that separates companies with a process from companies improvising.