How to Hire a Licensed Plumber for Your Home: What to Check Before You Hire

Water damage is the most common type of homeowner insurance claim in the United States, and plumbing failures — including those caused by improper installation by unlicensed plumbers — account for a significant share of those claims. Hiring a licensed plumber is one of the most important protections available to a homeowner, and verifying plumbing credentials takes less than five minutes.

What License Does a Plumber Need to Work in Your Home?

Plumbing licensing has two primary tiers in most states: Journeyman Plumber (a trained worker who performs plumbing under supervision) and Master Plumber (a fully licensed professional who can design, perform, and supervise plumbing systems). The plumbing company must also hold a Plumbing Contractor license to legally contract for plumbing work.

Master Plumber licenses are issued after candidates pass rigorous examinations and demonstrate years of journeyman experience. A master plumber has demonstrated competency in plumbing code, system design, backflow prevention, and fixture installation. For significant plumbing work — repiping a house, replacing a main sewer line, installing a water heater, or any work involving the main water supply — you want a master plumber or a company that employs one.

Plumbing contractor licensing requirements vary by state. Texas licenses through the Texas State Board of Plumbing Examiners. California uses the CSLB C-36 classification. Florida uses the DBPR. Washington uses L&I. Most states have online license lookup systems where you can verify credentials in minutes.

What Is Backflow Prevention and Why Does It Matter?

Backflow is the reversal of water flow in a plumbing system, which can allow contaminated water from irrigation systems, pools, or industrial equipment to flow backward into the drinking water supply. Backflow prevention devices — check valves, pressure vacuum breakers, and reduced pressure zone (RPZ) assemblies — prevent this.

Many jurisdictions require licensed backflow prevention specialists to install and test backflow prevention assemblies. Backflow testing is often required annually. An unlicensed plumber who is unfamiliar with backflow prevention requirements may install a plumbing system that violates local code and creates public health risks.

When hiring a plumber for any irrigation, pool, or commercial kitchen work, ask specifically about backflow prevention requirements in your jurisdiction. A licensed plumber will know the answer; an unlicensed operator may not even know the question is relevant.

What Permits Are Required for Plumbing Work?

Most plumbing work beyond simple fixture replacement requires a permit. Permitted work includes: water heater replacement (in most jurisdictions), sewer line replacement or repair, repiping, adding new fixtures, gas line work, and irrigation system installation. The permit process includes inspections at rough-in and completion stages, protecting you from hidden defects.

A plumber who suggests skipping a permit for a water heater replacement, sewer repair, or significant repiping project is creating risk for you. Unpermitted plumbing work can void your homeowner's insurance coverage for related water damage and must be disclosed as unpermitted work at the time of sale.

What Should You Ask a Plumber Before Hiring?

Essential pre-hire questions:

• “What is your plumbing license number, and is it a master plumber license?” For system-level work, a master plumber is preferable.
• “Does your company hold a plumbing contractor license?”Verify separately from the individual plumber's credentials.
• “Will you pull a permit for this work?” Required for most significant plumbing projects.
• “What warranty do you provide on labor?” A one-year labor warranty is typical minimum; longer warranties are better.
• “Are you familiar with this type of system?” Experience with your specific situation (slab leak, galvanized pipe repipe, tankless water heater) matters.

How Do You Avoid Plumbing Scams?

Common plumbing scams:

• Emergency up-sell: A plumber called for a minor leak recommends immediate full repiping. Get a second opinion before authorizing expensive emergency work.
• Sewer scope fraud: Charging for a sewer scope inspection but showing you footage from another property. Ask to watch the inspection in real-time.
• Unnecessary replacement: Recommending replacement when repair is possible. Ask specifically whether repair is an option before authorizing replacement.
• Parts markups: Charging 500% markups on parts is common in unethical plumbing operations. Compare parts prices online and ask for itemized billing.

Before hiring any plumber for significant work, verify their license at CheckLicensed.com. For $0.99, you get a complete license verification report including master/journeyman status, contractor license, current status, and any disciplinary history — essential protection before any plumbing project.