What Does a Plumber Do? Skills, Types and Qualifications

Plumbers install, repair and maintain the systems that bring clean water into a building and carry wastewater out, along with gas lines, water heaters and fixtures. In San Jose and South Bay homes, that often means working with older galvanized pipe, cast-iron drains and clay sewer laterals.

A good plumber is part technician, part detective and part teacher: finding the real cause of a problem, fixing it to code, and explaining the options.

Plumbers work with many materials, including copper, PEX, steel, cast iron and PVC, and with tools from basic wrenches to sewer cameras and hydro jetters. The trade has several specialties (residential, commercial, service and repair, construction and sanitary plumbing), and it takes a mix of mechanical skill, problem-solving, stamina and attention to detail.

What Is a Plumber?

A plumber is a skilled tradesperson who installs, maintains and repairs the piping systems that carry water, gas and waste in homes, businesses and industrial buildings. Their work protects health and safety: clean drinking water, sanitary drainage, and safe connections for water heaters, boilers and gas appliances.

What a plumber does day to day depends on their specialty. It ranges from installing pipes, fixtures and water heaters to clearing blocked drains, repairing leaks and broken lines, and making sure the work meets local codes. Residential plumbers work mostly in homes; commercial plumbers handle larger systems in offices, schools and hospitals; service and repair plumbers diagnose and fix problems in existing systems; and construction plumbers install plumbing in new buildings.

What Does a Plumber Do?

A plumber’s job is much more than fixing leaks. Plumbers make sure homes, businesses and public buildings have clean water, working drains and safe disposal of waste, and they prevent the water damage that follows when a system fails. The work falls into four main areas.

Installation

On new construction and remodels, plumbers lay out and install water lines, drain and vent piping, gas lines and fixtures like toilets, sinks, tubs and showers. They connect appliances such as water heaters, dishwashers and washing machines, install valves and fittings, and test the new system for leaks and proper flow. Work done right from the start lasts longer and protects the building.

Repair

Plumbers troubleshoot and fix leaks, clogs, broken pipes, running toilets, faulty water heaters and low water pressure. Prompt repairs limit water damage and mold, and keep small problems from turning into costly or hazardous ones.

Maintenance

Regular maintenance keeps a plumbing system working for longer: inspecting pipes and fixtures, cleaning drains, flushing water heaters, and checking for corrosion, slow leaks and wear. Preventive work catches minor issues before they become emergencies. For sewer lines, see sewer line maintenance tips and causes of sewer backups.

Diagnosis

Finding the real cause is a core skill. Plumbers use sewer cameras, pressure gauges, acoustic and thermal leak detection, and years of experience to locate hidden leaks in walls and slabs, failing fixtures and blockages deep in a line, so they fix the root cause and not just the symptom.

Licensed plumbers also handle permits and inspections for work that requires them, such as water heaters, repipes, sewer lines and gas piping.

How Plumbers Help Prevent Sewer Backups

A large share of a residential plumber’s maintenance work is keeping sewer lines flowing, because a backup is one of the messiest and most expensive problems a home can have. Plumbers clean and inspect the lines, but most backups start with what goes down the drains, so the household’s habits matter just as much.

Avoid Flushing Wipes, Grease and Hygiene Products

Wipes, cotton swabs, pads, tampons and paper towels don’t break down like toilet paper. They collect in the pipe, catch other waste and form dense blockages that lead to full backups. Even wipes labeled “flushable” don’t break apart the way toilet paper does. Put them in the trash, and keep a small bin in every bathroom so it’s easy.

Use Drain Screens and Hair Catchers

Screens and hair catchers over sink, tub and shower drains trap hair, food and soap scum before they reach the pipes. That keeps buildup out of the P-traps and branch lines that feed the main sewer line. Empty and rinse them often; they’re one of the cheapest preventive tools there is.

Never Pour Fats or Oils Down the Drain

Cooking fats, oils and grease (FOG) are liquid when hot but cool and harden inside the pipe, where they cling to the walls and catch other waste. Pour grease into a disposable container, let it cool and throw it in the trash, and wipe oily pans with a paper towel before washing them.

Install a Backwater Valve to Block Reverse Flow

A backwater valve is a one-way valve on the sewer line. It stays open for normal flow and closes if sewage starts flowing back toward the house, protecting the lowest fixtures, which are the first to overflow. It’s most useful where those fixtures sit low relative to the street sewer. It should be installed by a licensed plumber, with a permit.

Schedule Routine Sewer Line Cleaning

Even a well-used, well-maintained sewer line slowly collects grease, soap, scale and roots. Professional cleaning with a cable machine or hydro jetting removes the buildup and restores full flow. How often depends on the line: a camera inspection shows how fast it builds up, and older homes with clay laterals and street trees usually need it more often.

Inspect for Tree Roots and Pipe Cracks Regularly

Roots seek out the moisture in sewer lines, get in through small cracks and loose joints, and grow inside the pipe, where they catch waste and cause clogs. A sewer camera inspection finds roots and damage early, before they cause a backup. A plumber can cut the roots out and, if the pipe is damaged, recommend a repair or a trenchless liner.

Use a Grease Trap in Commercial Kitchens

Restaurants and other commercial kitchens send far more grease down the drains than a home does. A grease trap or interceptor separates fats, oils and food solids from the wastewater before they reach the sewer, and it has to be pumped and cleaned on a schedule to keep working. In San Jose, the City’s FOG Control Program inspects food service establishments and their grease control device maintenance records.

Educate Your Household on Safe Disposal Habits

Prevention only works if everyone follows it. One wipe or one pan of grease a week adds up. Make sure everyone in the home, including guests and kids, knows what goes in the trash instead of the drain; a small reminder by the kitchen sink helps.

What Should You Do If Your Sewer Is Already Backed Up?

Stop running water, flushing toilets and using the dishwasher or washing machine, keep people and pets away from any sewage, and call a plumber. Sewage carries bacteria, so don’t try to clean up a large overflow without protection. A plumber finds the blockage (often with a camera), clears it, and tells you whether roots, grease or a damaged pipe caused it and what will keep it from happening again. CPI offers same-day service in San Jose and the South Bay; see emergency plumber and causes of sewer backups.

What Plumbing Skills Are Required to Be a Good Plumber?

A good plumber combines technical knowledge with physical ability and people skills. Codes, materials and equipment keep changing, so learning never really stops. See essential plumbing skills for more detail.

Mechanical Skills

Plumbers work with a wide range of tools and machinery, from wrenches, pipe cutters and press tools to drain machines and cameras, and with many pipe materials. Choosing the right tool and method for each job, and recognizing a faulty part or the source of a blockage, is what makes repairs and installations last.

Physical Skills

The job takes strength to lift pipe, fixtures and equipment, stamina for long days, and flexibility to work in crawl spaces, attics and under sinks. Fine motor skills matter too, for small parts and precise adjustments.

Application of Principles

Plumbing applies math and physical science: water pressure, flow, gravity drainage and slope, venting, and geometry for angles and offsets. Plumbers use these to size pipes, lay out systems that meet code, and work out why a system isn’t performing.

Problem-Solving

Plumbing problems rarely look the same twice. A plumber reads the symptoms (a leak, a slow drain, low pressure, an odor), works out the likely causes, and picks the best fix, often under time pressure and sometimes in the middle of an emergency.

Administrative Skills

Scheduling, estimates, invoices, permits, material orders and job records are part of the work, especially for plumbers who lead jobs or run a business. Good organization keeps projects on time and customers informed.

Communication Skills

Plumbers explain problems and options to homeowners in plain language, coordinate with contractors and inspectors, and work as part of a crew. Clear communication builds trust and avoids surprises.

Is Plumbing the Right Career for You?

Ask yourself a few questions:

• Do you enjoy solving practical, hands-on problems?
• Are you comfortable working in tight, confined spaces?
• Can you handle physically demanding work?
• Are you willing to keep learning as codes and technology change?

If you answered yes to most, plumbing may be a good fit.

Different Types of Plumbers

Plumbers specialize by setting and type of work. Many work across more than one area during a career, and the variety is one of the trade’s draws.

Residential Plumbers

Residential plumbers work in houses, condos and apartments. They install and maintain water supply and drain lines, water heaters, toilets, sinks and showers, and handle hidden leaks, clogs and appliance hookups. Most of the plumbers homeowners call are residential service and repair plumbers.

Commercial Plumbers

Commercial plumbers work on larger systems in businesses, schools, hospitals, restaurants, apartment buildings and public buildings. They install and maintain complex, high-use systems with larger pipe, more fixtures, grease interceptors and backflow devices, and they work to commercial code requirements.

Service and Repair Plumbers

Service and repair plumbers diagnose and fix problems in existing systems, in homes and businesses alike. They answer emergency calls, clear clogs, repair leaks and broken fixtures, and do preventive maintenance and inspections.

Construction Plumbers

Construction plumbers install plumbing in new buildings and major remodels. They follow the plans, coordinate with the general contractor and other trades, and install systems that pass inspection from the rough-in to the final.

Sanitary Plumbers

Sanitary plumbers specialize in drainage and waste: drain and sewer lines, toilets, and sewer laterals. Their work keeps wastewater flowing safely away from the building and protects public health. In homes, this includes hydro jetting, sewer camera inspection and trenchless sewer repair.

What Qualifications Are Needed to Become a Plumber?

Most plumbers learn the trade through an apprenticeship that combines paid on-the-job training with classroom instruction. According to the U.S. Bureau of Labor Statistics, apprenticeships typically last four or five years, with about 2,000 hours of paid on-the-job training each year. See plumber certifications for the details.

Educational Requirements

A high school diploma or equivalent (such as a GED) is the usual starting point. Some plumbers take vocational or community college courses before or during an apprenticeship, covering pipefitting, blueprint reading, safety and plumbing codes. Math and science help: plumbers apply them to pressure, flow and pipe sizing every day.

Certification and Licensing

California doesn’t issue a separate state journeyman or master plumber license, as some states do. “Journeyman” and “master” describe experience levels, often used in union and employer programs. The state license is the contractor’s license from the Contractors State License Board (CSLB): plumbing contractors hold the C-36 classification. To get one, CSLB requires at least four years of journey-level experience in the last ten years, with partial credit for an apprenticeship or related schooling, plus passing a trade exam and a law and business exam and carrying a bond.

A licensed contractor can contract for plumbing jobs and pull permits; plumbers who work for a licensed contractor do the work under that license. Plumbers also keep up with the California Plumbing Code, which is updated on a three-year cycle, and with new materials and equipment. Check any contractor’s license on the CSLB website.

On-the-Job Training

Hands-on experience is where plumbers really learn the trade. Apprentices work under experienced plumbers on repairs, remodels and new work, while attending classes in code, safety and theory. In California, apprenticeship programs are registered with the state Division of Apprenticeship Standards; in Santa Clara and San Benito Counties, the plumbers’ union apprenticeship is run by UA Local 393, and many employers train apprentices too. CPI Service runs its own apprenticeship programs.

Career stage	What the work involves	How you get there
Apprentice	Learns on the job under experienced plumbers; attends classes	Enter an apprenticeship program
Journey-level plumber	Works independently on installations, repairs and service	Complete an apprenticeship or equivalent experience
Lead, foreman or master plumber	Leads crews and complex jobs, trains apprentices	Years of journey-level work
Licensed contractor	Runs a plumbing business, contracts jobs, pulls permits	CSLB C-36 license: four years of journey-level experience, exams, bond

How Much Does a Plumber Make?

Plumbing pays well compared with many careers, and pay grows with experience. It varies with location, specialty, union membership and whether a plumber works for a company or runs their own business. Plumbers in commercial or industrial work, those with extra credentials, and business owners tend to earn more. Demand is steady: BLS projects employment to grow 7% from 2025 to 2035, much faster than average.

Salary Ranges and Earning Potential

National pay for plumbers, pipefitters and steamfitters, May 2025 (U.S. Bureau of Labor Statistics):

Measure (national)	Annual wage
Lowest 10% earned less than	$44,150
Median	$63,800 ($30.67 an hour)
Highest 10% earned more than	$108,420
Median at plumbing, heating and air-conditioning contractors	$63,010
Median in government	$71,660

Apprentices earn less than fully trained plumbers, and their pay rises as they learn. These are national figures; pay in the Bay Area differs. For what plumbing work costs homeowners, which is a different thing from what plumbers earn, see plumber cost in San Jose.

What Is the Work Environment of a Plumber Like?

Plumbers work in private homes, commercial buildings, construction sites and industrial facilities, and the setting can change from one call to the next: a finished kitchen in the morning, a dusty job site in the afternoon. The work is often in tight spaces such as under sinks, behind walls, in crawl spaces and attics, and in trenches outdoors, in every kind of weather.

It’s physical work: lifting heavy pipe and tools, standing, kneeling or crouching for long periods. Most plumbers work full time, and emergencies mean evening and weekend calls are common.

A Typical Day

A typical day for a residential service plumber might look like this:

• Morning: review the day’s work orders, load the truck, and head to the first call.
• Mid-morning: fix a water heater that isn’t heating properly and check that it’s safe.
• Midday: lunch, often on the road between calls.
• Afternoon: diagnose and clear a blocked drain with a drain snake or hydro jetter.
• End of day: test the work, explain what was done, and finish the paperwork.

What Are the Essential Plumbing Tools?

The right tools let plumbers work safely, quickly and accurately. Common ones include:

• Wrenches (pipe, adjustable and basin wrenches) for fittings and fixtures
• Pipe cutters and saws for clean cuts in copper, PEX and plastic
• Plungers and drain snakes for clogs
• Hydro jetters for grease, scale and roots in drain and sewer lines
• Sewer cameras to see inside lines and find problems
• Pressure gauges and leak detection equipment for hidden leaks

See essential plumbing tools.

How to Choose the Right Plumber for Your Needs

The right plumber gets the job done correctly the first time and avoids costly mistakes. Look for experience with the kind of work you need, and check:

• A valid CSLB license and insurance
• Clear, fixed pricing before work starts; see plumber cost in San Jose
• Willingness to explain the problem and your options
• Permits pulled when required
• Recent local reviews that mention honesty, punctuality and cleanliness

Plumber vs. DIY: When to Call a Professional

Homeowners can handle simple tasks like plunging a toilet or replacing a faucet aerator. Call a licensed plumber for:

• A leaking pipe, or a faucet leak you can’t stop
• A drain that stays blocked after plunging
• A toilet that keeps running after you’ve replaced the flapper
• Low water pressure throughout the house
• Water heater problems beyond the basics
• Anything involving gas, sewer lines or work that needs a permit

When in doubt, call a professional. It’s safer, and it keeps the work to code.

Plumbers in San Jose

• Older homes: many South Bay homes have galvanized pipe, cast-iron drains and clay laterals that call for experience.
• Permits: water heaters, repipes and sewer work need City of San Jose permits.
• Emergencies: burst pipes and sewer backups don’t wait; CPI answers emergencies at (408) 978-3093. Meet our team.

CPI Service provides plumbing throughout San Jose and the South Bay. Request a free estimate or call (408) 978-3093.