How to Hire a Plumber: Questions to Ask and Red Flags

Most homeowners hire a plumber under pressure, after a toilet overflows or a pipe bursts, and that urgency is exactly when shortcuts get taken that lead to expensive follow-up work. The plumbers who charge the least upfront are frequently the ones pulling permits and the ones who disappear when a leak shows up in the ceiling below a newly installed toilet. A small amount of vetting before the first tool is placed pays for itself many times over in avoided callbacks, insurance disputes, and repair costs.

This guide uses published state licensing data, plumbing code frameworks, contractor insurance standards, and patterns from thousands of aggregated homeowner reports to give you a clear, sequential process for finding, vetting, hiring, and managing a plumber for any toilet or bathroom plumbing job. The goal is to make you a prepared buyer so the plumber you hire is the last one you need for this job. For the toilet models most plumbers are asked to set, see our pillar guide to the best flushing toilets, which covers TOTO, Kohler, American Standard, Woodbridge, and Gerber models by flush performance and rough-in compatibility.

Where do you find a qualified plumber?

The single most reliable source of plumber referrals is someone whose house has similar plumbing to yours, because they have already tested the contractor on comparable work. A plumber who correctly set a TOTO Drake on a 12-inch rough-in in a neighbor's house has demonstrated the most common residential toilet install. Word-of-mouth referrals carry weight because a plumber who does poor work quickly loses neighborhood referrals.

Online review platforms give you a broader pool. Angi, HomeAdvisor, and Thumbtack all require basic credentialing in most states, but the screening depth varies by platform and by state. Use them to build a shortlist of three to five contractors, then independently confirm each one on your state licensing board's public lookup tool before you contact them. A plumber who looks good on a platform but does not appear in the state licensing database is an immediate disqualification.

What questions should you ask a plumber before hiring?

The phone call or first meeting with a plumber is where the most important vetting happens, and the questions you ask reveal more than the answers alone. A qualified plumber has heard every one of these questions many times and answers them without irritation or deflection. A plumber who bristles at being asked for a license number is telling you something important.

License and credential questions

Every plumber doing residential work for pay must hold a state plumber's license in the vast majority of states. Ask for the license number and look it up on your state licensing board's website before the conversation goes further. Licensing requirements vary: some states use a master plumber designation for those who can pull permits and supervise journeymen, others have journeyman licenses for field work only. For a toilet install or repair, a journeyman working under a licensed master plumber is typically sufficient. For a full bathroom rough-in or any work that requires a permit, a master license holder or a licensed contractor who employs one is required in most jurisdictions.

• What is your state plumber's license number, and is it current?
• Is your license a journeyman license, master license, or contractor license?
• How long have you been licensed in this state?
• Do you have experience setting [the specific model, e.g., TOTO Drake II, Kohler Highline, American Standard Champion 4]?

Insurance questions

Two types of insurance are non-negotiable before any plumber enters your home. General liability covers property damage the plumber causes during work, such as a cracked tile or a water leak from an improperly seated wax ring. Workers' compensation covers the plumber or their employees if they are injured on your property. Without workers' comp, an injury to an unlicensed worker on your job can expose you to a lawsuit that your homeowner's insurance may not fully cover. Ask for a certificate of insurance from the carrier directly, not a photocopy, and confirm the policy is current.

• Do you carry general liability insurance? What is your coverage limit?
• Do you carry workers' compensation for all employees and subcontractors on this job?
• Can your insurance carrier email a current certificate of insurance directly to me before work starts?

Permit and code questions

Most toilet replacements on a standard rough-in do not require a permit in most jurisdictions, because you are replacing a fixture, not altering the plumbing system. However, moving a toilet flange, changing drain line size, adding a new fixture, or roughing in for a new bathroom always requires a permit and inspection. A plumber who volunteers to skip a permit to save you money is transferring their legal risk onto you: if the un-permitted work is discovered in a home sale inspection or causes a later failure, the liability is yours, not theirs.

• Does this specific job require a permit in my municipality?
• If a permit is required, will you pull it, and does your quote include permit fees?
• Who schedules the inspection once work is complete?

Pricing and scope questions

Plumbing pricing uses two models: flat-rate or fixed-price per job, and time-and-materials where you pay an hourly rate plus parts. Flat-rate pricing is predictable and common for standard jobs like toilet installation, which typically runs $150 to $350 for labor in most markets in 2026 based on aggregated contractor data, not including the toilet. Time-and-materials can be appropriate for complex diagnostic work where the scope is unknown, but require a clear hourly rate and a not-to-exceed ceiling before work starts.

• Do you price this job flat-rate or time-and-materials?
• What exactly is included in the quoted price, and what would add cost?
• Are parts and materials itemized separately or bundled into the price?
• What is your policy if the job runs over scope?
• What is your payment schedule, and what form of payment do you accept?

What should a written plumbing quote include?

The written quote is the legal document that defines the job. Before you sign anything, read the scope of work line by line and ask for clarification on anything ambiguous. If the quote says "install toilet" without naming the model, ask for the make and model to be added, because a contractor who replaces your TOTO UltraMax II with a no-name fixture and says the quote just said "toilet" has no obligation to upgrade without additional cost.

The scope should also define what the plumber does if they encounter something unexpected, like a corroded flange, a non-standard rough-in distance, or a damaged supply line. Reputable plumbers include a clause that explains how change-orders are priced and approved, requiring your written sign-off before any additional work begins. If the quote contains no change-order language, add it before signing or walk away.

What are the red flags that mean you should not hire this plumber?

Red flags fall into two phases: the vetting phase before you hire, and the job-day phase once the plumber is on site. Both are worth knowing because some contractors who pass early vetting reveal problems once work begins.

Pre-hire red flags

• No license or a license that cannot be verified. The state licensing board's public tool is free and takes 30 seconds. If the number does not appear, or the name on the license does not match the person or company quoting the job, do not hire them.
• Refuses to show insurance documentation. Legitimate insurance policies allow a certificate to be sent to any client requesting it. Inability to provide one means the insurance may not exist.
• Significantly the lowest bid. A quote that is 40 to 50 percent below the other two quotes you received almost always reflects a missing cost: no insurance, no permit, substandard parts, or a scope that omits the work that makes the others more expensive.
• Demands full payment upfront. A standard payment structure for residential plumbing is a small deposit (10 to 15 percent) at signing and the balance upon satisfactory completion. Full upfront payment removes your primary leverage for getting problems corrected.
• Offers to skip the permit. This puts legal liability on the homeowner. A plumber who skips permits regularly is also likely to skip the inspections that catch code violations before they become expensive failures.
• No written quote. A verbal agreement cannot be enforced. Any contractor unwilling to put the scope and price in writing is not a contractor you can hold accountable.
• Pressures you to decide immediately. Legitimate plumbers are busy but not so desperate that they need you to decide in the next hour. Artificial urgency is a sales tactic designed to prevent you from getting competing quotes.

On-site red flags

• Arrives without the materials named in the quote. If your quote specifies a TOTO Drake and the plumber arrives with a different model, stop work until the discrepancy is resolved in writing.
• Cannot explain the work plan before starting. A plumber who hesitates or gives vague answers when asked to walk you through what they are about to do is not a plumber who has done this job many times.
• Discovers significant new problems before doing any visible work. One of the oldest scam patterns in home services is the contractor who discovers a catastrophic problem that requires additional emergency work before anything can be finished. It does happen legitimately, but the timing, before a single fixture has been touched, is a meaningful warning sign. Ask to see the problem, ask what the code violation or damage actually is, and consider a second opinion before authorizing additional work.
• Asks for more money mid-job without a written change order. Any scope change that adds cost requires your written authorization before work continues. A plumber who asks verbally and keeps working before you agree is removing your ability to dispute the additional charge.
• Does not test the work before leaving. Every toilet installation should end with multiple flushes, a check of the supply line and shut-off valve for drips, a check of the wax seal area for seepage, and a confirmed water level in the tank. A plumber who installs a toilet without testing it has not finished the job.

How do you compare multiple plumber quotes fairly?

Getting three quotes is the standard recommendation, and the reasoning is sound: two quotes give you no basis for identifying an outlier, but three give you a market range for the job in your area. When requesting quotes, give every plumber the same written description of the job so you are comparing like with like. Include the make and model of the toilet if you have already purchased it, the rough-in distance, whether the old toilet needs to be removed and hauled away, and any known complication like an older flange or a non-standard supply line angle.

When the quotes arrive, build a simple comparison that adjusts each for what is included and excluded. Common items that vary between quotes:

• Permit fee (commonly $50 to $150 depending on municipality)
• Removal and disposal of the old toilet (commonly $25 to $75)
• New wax ring and closet bolts (commonly $15 to $30 in parts)
• New supply line if the existing one is corroded or an older braided style
• Seat installation if not pre-installed on the toilet
• Caulking around the base

Once you have adjusted the totals, weigh them against what you learned in the vetting phase. A licensed, insured plumber who pulls permits and provides a written warranty is worth a modest premium over the unlicensed alternative, because the cost of one callback or one insurance dispute will exceed any initial saving.

What should you check after the plumber finishes?

The walk-through after a plumbing job is where many homeowners skip the verification that would have caught a problem while the plumber was still on site and still responsible for fixing it at no additional cost. Take five minutes to run through the following before you sign off or release payment.

Post-job checklist for a toilet installation

• Flush the toilet five to ten times and observe the flush strength. A new toilet like the American Standard Champion 4 or the TOTO Drake should clear the bowl completely in a single flush without running double. If the flush seems weak, ask the plumber to check the fill valve adjustment and the flapper chain tension before they leave.
• Watch the base of the toilet during and immediately after flushing for any water seeping from beneath the bowl. Any moisture at the base indicates either an improperly seated wax ring or a cracked flange that was not disclosed before installation. This must be corrected before the plumber leaves.
• Check the supply line connection at both ends: the shut-off valve on the wall and the fill valve at the bottom of the tank. Finger-tighten both and look for drips after the tank fills.
• Confirm the tank fills to the correct water level and the fill valve shuts off completely. A fill valve that continues to trickle indicates it needs adjustment or replacement.
• Sit on the toilet and move side to side to test for rocking. A toilet that rocks on the floor is either missing shims on an uneven floor, has loose closet bolts, or has a flange that is not sitting correctly. All three are the plumber's responsibility to correct before leaving.
• Confirm the seat is secured. Soft-close seats like those on Woodbridge and Swiss Madison toilets require tightening the hinge bolts, and a seat that slides or rotates is not properly installed.

For permit-required work such as a new bathroom rough-in, a flange repair, or a drain line alteration, the inspection sign-off is more important than your personal walk-through. The inspector who visits the site is checking against the local plumbing code, not just for obvious leaks, and catching code violations at inspection is the lowest-cost time to fix them. Do not make final payment, or release any payment held pending completion, until the inspection has passed.

Warranty and documentation

Before the plumber leaves, collect the following in writing or confirm where to obtain them:

• The plumber's labor warranty: how long they cover the workmanship, what it covers, and how to make a warranty claim.
• The manufacturer's warranty documentation for any fixtures installed. TOTO covers manufacturing defects for one year on most parts and longer on vitreous china. Kohler's limited lifetime warranty covers most residential fixtures against defects. American Standard, Woodbridge, and Swiss Madison each publish their own warranty terms. Keep the model number and installation date.
• The permit number and the date the inspection passed, if applicable. This is a document you keep permanently and disclose in a future home sale if asked about plumbing work.
• Any parts or manuals that came with the toilet. Soft-close seat adjustment instructions, touchless flush battery replacement guides, and dual-flush button adjustment notes are all in the product documentation and useful years later.

What does it cost to hire a plumber for common toilet jobs?

Understanding the cost ranges for common jobs before you call a plumber gives you an immediate calibration for whether a quote is reasonable or suspicious. An extremely low quote on a toilet installation is almost always missing something, whether that is a permit, insurance, or the material costs being shifted to you as a separate invoice.

The wide range in toilet installation pricing reflects the market variability between regions and between plumbers within the same market. Urban markets in the Northeast and West Coast tend toward the higher end of the range. Rural markets and areas with lower cost of living trend lower. Emergency or after-hours rates add 50 to 100 percent to standard pricing across all job types.

If you have already purchased the toilet and need a plumber to set it, the most cost-effective approach is to have the toilet on site, unboxed and in the bathroom if possible, before the plumber arrives. Time the plumber does not spend carrying a toilet from a vehicle or a garage is time they are not billing for. EPA WaterSense certified toilets like the TOTO Aquia IV dual-flush and the Kohler Cimarron are not more difficult to install than a standard gravity-feed toilet; the 0.8 and 1.28 GPF dual-flush mechanism is entirely in the tank and does not affect the rough-in or the flange connection.

When does a toilet installation cost more than expected?

The most common cost surprises in toilet installations come from three sources: a corroded or broken flange, a non-standard rough-in distance, and water damage under the subfloor that was hidden by the old toilet. A corroded flange can sometimes be repaired with a flange extender or repair ring, which adds $50 to $100 to the job. A broken cast-iron flange requires replacement, which is a larger repair. A toilet with a 10-inch or 14-inch rough-in instead of the standard 12-inch requires the matching toilet model; if you have already purchased a standard model it may need to be returned and exchanged. Water damage under the subfloor can range from a simple dry-out to significant subfloor replacement and should be handled before the new toilet is set.

A responsible plumber will photograph any complication they discover before proceeding, show you the problem, explain the repair options in plain language, give you a written change-order with the additional cost, and wait for your authorization before doing any additional work. A plumber who discovers a "catastrophic problem" and begins work on it before explaining it to you is one to monitor carefully.

Frequently Asked Questions

Do I need a licensed plumber to install a toilet?

In most states, a simple toilet replacement on an existing standard rough-in does not legally require a licensed plumber, and many homeowners complete this job themselves. However, any work that alters the drain, vent, or supply plumbing typically requires a licensed plumber and a permit. Even for a simple swap, hiring a licensed plumber protects you if a leak develops later, because the plumber's liability insurance covers the damage rather than your homeowner's policy.

How do I verify a plumber's license?

Every state has a contractor licensing board or department of consumer affairs that operates a free public license lookup tool online. Search for "[your state] plumber license lookup" and enter the license number the plumber provides. Confirm the license type (journeyman, master, or contractor), the expiration date, and that the name matches the contractor or company you are hiring. This takes less than two minutes and is the single most important vetting step.

What is the difference between a master plumber and a journeyman plumber?

A journeyman plumber has completed an apprenticeship and passed a journeyman exam, qualifying them to do plumbing work under the supervision of a master plumber. A master plumber has additional experience and has passed a master-level exam, qualifying them to pull permits, run a plumbing business, and supervise journeymen. For a standard toilet installation, a journeyman working under a licensed contractor is sufficient. For permitted work requiring a signature on drawings or a permit application, a master plumber is typically required.

What insurance should a plumber carry?

A plumber doing residential work should carry general liability insurance (typically a minimum of $1 million per occurrence) to cover property damage they cause, and workers' compensation insurance to cover their employees or themselves if injured on your property. In some states workers' compensation is required even for sole proprietors doing residential work. Ask for a certificate of insurance from the carrier before work starts.

Should I buy my own toilet or let the plumber supply it?

Buying your own toilet gives you full control over the model and gives you direct access to the manufacturer's warranty. TOTO, Kohler, American Standard, Woodbridge, Swiss Madison, and Gerber all publish their warranty terms, and they run to the homeowner who registers the product, not to the installer. The tradeoff is that if the toilet arrives damaged, you are responsible for the exchange, not the plumber. Most homeowners buying a specific model for performance reasons, such as the TOTO Drake II for its MaP-tested 1,000 gram flush score or the American Standard Champion 4 for its large 2-3/8 inch trapway, are better served buying the toilet themselves.

What is a reasonable deposit for plumbing work?

A reasonable deposit for residential plumbing work is 10 to 15 percent of the total quote, or an amount sufficient to cover materials the plumber must purchase before the job starts. A deposit of more than 25 to 30 percent should be questioned, and any demand for full payment before work begins is a major red flag. The balance is paid upon satisfactory completion, giving you leverage to have any problems corrected before the plumber is fully paid.

Should I get multiple quotes for a toilet installation?

Yes. Three quotes give you a market range for the job in your area and make outliers easy to identify. Getting competing quotes also signals to each plumber that they are competing for the job, which tends to produce more realistic pricing. For a simple toilet installation the quotes will likely be close; for a more complex job like a flange repair or a bathroom rough-in, the range between quotes can be significant.

Do I need a permit to replace a toilet?

In most jurisdictions, replacing a toilet on the same rough-in without moving the flange does not require a permit, because you are replacing a fixture rather than altering the plumbing system. Moving the flange, changing drain line size, adding a toilet to a space that had none, or doing any work that alters the venting typically does require a permit. When in doubt, ask your municipal building department, not the plumber, since the plumber benefits financially from not pulling a permit.

How long does a toilet installation take?

A standard toilet swap on a standard 12-inch rough-in with no complications takes a licensed plumber 45 minutes to 90 minutes from start to finish, including removing the old toilet, setting the wax ring, installing the new toilet, connecting the supply line, and testing. Jobs with a corroded flange, a non-standard rough-in, or water damage under the subfloor add time and scope. A plumber who quotes more than three hours for a simple swap without a clear reason for the additional time should be questioned.

What should I do to prepare before the plumber arrives?

Clear a path to the bathroom and remove any items under the vanity or near the toilet. Turn off the water supply to the toilet at the shut-off valve if you know how to do this safely. Have the toilet unboxed and in the bathroom if you purchased it yourself. Locate the wax ring and supply line if you purchased them separately. Take a photo of the existing toilet's make and model before it is removed, which is useful if any warranty or parts question arises later.

How do I know if a plumber is overcharging me?

Compare the quote to the market ranges for your job type, get at least two other quotes for the same scope, and research the retail cost of any parts or fixtures included in the quote. Plumbers typically mark up parts and materials, which is standard practice. A markup of 20 to 30 percent above their wholesale cost is common and reasonable. A quote that charges retail price plus a high markup for the same fixture you could buy at retail is worth negotiating. The best protection is the third quote: if two plumbers quoted $275 and $310 and the third quoted $650 for the same scope, the outlier has revealed itself.

What is a change order and when should I expect one?

A change order is a written document that adds to or modifies the original scope of work and its price. You should expect a change order whenever something discovered during the job adds work that was not in the original quote, such as a broken flange, a damaged subfloor, or a corroded supply stub-out. The change order should describe the additional work, the additional cost, and require your signature before any additional work begins. Never authorize additional work verbally; always get it in writing first.

What is the most common toilet installation mistake plumbers make?

Based on patterns across thousands of aggregated homeowner reports, the most common installation mistake is failing to shim a toilet on an uneven floor before caulking the base. A toilet that is not properly leveled and shimmed rocks when sat on, eventually breaking the wax seal. The second most common mistake is over-tightening the closet bolts, which cracks the porcelain at the mounting holes. Both are correctable during the post-job walk-through if you test before the plumber leaves.

Can a plumber install an EPA WaterSense toilet the same as a standard toilet?

Yes. An EPA WaterSense certified toilet at 1.28 GPF or 1.0 GPF uses the same standard rough-in dimensions (typically 12 inches), the same wax ring, and the same supply line as an older 1.6 GPF toilet. The water savings come from the flush valve and tank design, not from any change to the rough-in or drain plumbing. Toilets like the TOTO Aquia IV at 0.8 and 1.28 GPF dual flush and the Gerber Avalanche at 1.0 GPF are no more complex to install than a 1.6 GPF model.

What happens if the plumber damages something during the job?

If the plumber carries general liability insurance, property damage they cause during the job should be covered by their policy. Document any damage with photographs immediately, before anything is moved or cleaned up. Notify the plumber in writing (a text or email is sufficient for the record) and ask for their insurance carrier's contact information. If the plumber denies responsibility or their insurance does not respond, your homeowner's insurance is the next line of coverage, though you will likely owe a deductible. This is why verifying insurance before the job starts is non-negotiable.

Is it safe to hire a plumber found on Craigslist or Facebook Marketplace?

It is not automatically unsafe, but it requires the same vetting as any other source and in practice the screening is often lower. Always verify the license number independently on your state board's website, always request a certificate of insurance from the carrier, and always get a written quote before work begins. The lower overhead of an independent contractor found through informal channels can translate to genuinely lower prices, but the same red flags apply: no license, no insurance, and no written quote are dealbreakers regardless of where you found the plumber.

How do I handle a dispute with a plumber after the job is done?

Start by putting your complaint in writing and sending it to the plumber by email, which creates a dated record. Give them a reasonable time to respond and correct the issue, typically five to ten business days for a non-emergency. If the plumber does not respond or disputes responsibility, file a complaint with your state contractor licensing board, which is the regulatory body with authority over licensed contractors. For financial disputes, small claims court handles amounts typically up to $5,000 to $10,000 depending on the state. If the dispute involves insurance, contact the plumber's carrier directly using the certificate of insurance you retained before work began.

Should I tip a plumber?

Tipping is not expected or standard in the plumbing trade the way it is in the service and hospitality industry. Plumbers are skilled tradespeople charging professional rates. If a plumber goes significantly above and beyond, handles an emergency quickly and professionally, or solves a problem that multiple others failed to diagnose, a tip is a genuine gesture of appreciation but is not obligatory and is not expected in standard residential plumbing work.

What brands of toilets are plumbers most familiar with?

Licensed residential plumbers routinely install TOTO, Kohler, American Standard, Gerber, and Woodbridge toilets, as these are the most widely distributed brands through plumbing supply houses and big-box retailers. TOTO Drake, Drake II, and UltraMax II, Kohler Highline and Cimarron, American Standard Champion 4 and Cadet 3, and Gerber Avalanche are the models that come up most often in residential installs. Swiss Madison toilets and Woodbridge one-piece models are increasingly common as they have expanded distribution. If you are installing a less common brand or a smart toilet with electrical requirements, confirm beforehand that the plumber has installed that specific model or a similar one.

Sources

• EPA WaterSense, epa.gov/watersense
• MaP flush testing, map-testing.com
• Manufacturer published specifications
• National Association of Plumbing-Heating-Cooling Contractors (NAPHCC), phccweb.org
• State contractor licensing boards (public license lookup tools)
• HomeAdvisor True Cost Guide, homeadvisor.com/cost/plumbing