The Complete Guide to Becoming a Plumber

Definitions & Terms to Know

Licensed plumber

A plumber who has met state or local requirements (education, apprenticeship, and exams) and holds a valid license to perform plumbing work. Licensing protects consumers by ensuring the professional knows codes and safety practices.

Journeyman plumber

A plumber who has completed an apprenticeship (typically 4–5 years) and passed a journeyman exam. They can work independently under the general oversight of a master plumber. Requirements vary by state.

Master plumber

A plumber who has met additional experience and exam requirements beyond the journeyman level. A master can pull permits, run a business, and supervise journeymen and apprentices. Not all states use this tier.

Tankless water heater

A water heater that heats water on demand as it flows through the unit, rather than storing hot water in a tank. Tankless units are more energy-efficient and last longer (20+ years) but have higher upfront costs.

Sump pump

A pump installed in a basement or crawl space pit that automatically removes accumulated water to prevent flooding. Essential in areas with high water tables or heavy rainfall. Battery backup models protect against power-outage flooding.

Backflow preventer

A device installed on a water line to stop contaminated water from flowing backward into the clean supply. Required by plumbing codes at certain connection points — irrigation systems, boilers, and commercial kitchens often need one. Annual testing is typically mandatory.

Septic system

An on-site wastewater treatment system used in areas without municipal sewer. Wastewater flows into a buried tank where solids settle and bacteria break down waste; liquid drains into a leach field. Septic tanks should be pumped every 3–5 years by a licensed professional.

Slab leak

A water leak in the copper or PEX pipes that run beneath a home's concrete slab foundation. Slab leaks are caused by corrosion, shifting soil, or poor installation. Warning signs include hot spots on the floor, the sound of running water when all fixtures are off, unexplained increases in the water bill, and cracks in the foundation. Detection typically involves acoustic listening equipment or infrared cameras. Repair methods include spot repair (jackhammering through the slab to fix the pipe), rerouting the line through the ceiling or walls, or epoxy pipe lining. Costs range from $500 for a simple spot repair to $3,000–$5,000 for rerouting.

Water hammer arrestor

A small plumbing device installed near valves and appliances to absorb the shockwave that occurs when water flow is suddenly stopped — the loud banging noise known as water hammer. Arrestors contain a sealed air chamber and a piston that compresses when the pressure spike hits, cushioning the impact. They're installed on washing machine supply lines, dishwasher connections, and near quick-closing solenoid valves. A water hammer arrestor costs $10–$30 for the part and $100–$200 installed by a plumber. Without one, water hammer can loosen pipe joints, damage valves, and eventually cause leaks.

PEX piping

Cross-linked polyethylene (PEX) tubing used for residential water supply lines. PEX has largely replaced copper in new construction and repiping because it's flexible (bends around corners without elbow fittings), resists corrosion and scale buildup, handles freeze-thaw cycles better than rigid pipe (it can expand without bursting), and costs 25–40% less than copper for materials and labor. PEX comes in three types: PEX-A (most flexible, best for tight bends), PEX-B (most common, good balance of cost and performance), and PEX-C (least flexible, lowest cost). It's connected using crimp rings, clamp rings, or expansion fittings. Repiping a typical home from copper to PEX costs $4,000–$8,000 versus $8,000–$15,000 for copper-to-copper.

Expansion tank

A small pressurized tank (typically 2–5 gallons for residential use) connected to a water heater or hydronic heating system that absorbs excess pressure caused by thermal expansion. When water heats up it expands — a 40-gallon tank produces about half a gallon of expanded water per heating cycle. Without an expansion tank, that pressure has nowhere to go and stresses the water heater tank, valves, and supply lines, leading to premature failure, dripping T&P (temperature and pressure) relief valves, and even burst pipes. Expansion tanks are now required by code in most jurisdictions when a closed water system is present (meaning the home has a check valve, pressure-reducing valve, or backflow preventer that prevents expanded water from pushing back into the municipal supply). The tank contains a rubber bladder separating an air charge (pre-set to match the home's water pressure, typically 40–80 PSI) from the water side. Over time the bladder can fail, becoming waterlogged — a sign is the T&P valve periodically dripping. A plumber can test the tank by pressing the Schrader valve on top: if water comes out instead of air, the bladder has failed and the tank needs replacement. Cost: $150–$350 installed. Lifespan: 5–10 years depending on water quality and pressure.

Polybutylene pipe

A gray plastic water supply pipe (stamped 'PB2110') widely installed in U.S. homes from 1978 to 1995 as an inexpensive alternative to copper. Polybutylene was eventually found to deteriorate from the inside out when exposed to chlorine and other oxidants in public water supplies — micro-fractures develop in the pipe walls over 10–25 years, leading to sudden, catastrophic leaks with no visible warning. An estimated 6–10 million homes in the U.S. were plumbed with polybutylene. Most plumbing professionals recommend full re-piping with PEX or copper ($4,000–$15,000 for a typical home) rather than spot repairs, because failure is progressive and unpredictable. Many insurance companies will not insure homes with polybutylene supply lines, and its presence can affect resale value. Polybutylene is easy to identify: gray (sometimes white or black) flexible tubing, typically 1/2" to 1" diameter, with copper or plastic crimp rings at connections.

Galvanized pipe

Steel pipe coated with a layer of zinc to resist corrosion, used as the standard for residential water supply and drain lines from the 1930s through the 1960s. While the zinc coating initially protects against rust, it gradually corrodes from the inside over 40–70 years, building up mineral deposits that restrict water flow and eventually cause pinhole leaks. Homes still plumbed with galvanized pipes commonly experience low water pressure, rusty or discolored water (especially when taps are first opened), and frequent small leaks at threaded joints. A plumber can identify galvanized pipe by its gray exterior and threaded fittings — a magnet will stick to it (unlike copper). Repair options range from spot replacement of corroded sections ($200–$600) to full re-piping with copper or PEX ($3,000–$12,000), which is recommended when corrosion is widespread.

Ball valve

A quarter-turn shut-off valve that uses a hollow, perforated, pivoting ball to control water flow. Turning the handle 90 degrees opens or closes the valve completely. Ball valves are the modern standard for main water shut-offs and branch supply lines because they are more reliable than older gate valves — they rarely seize, require no maintenance, and provide a clear visual indicator (handle parallel to the pipe = open, perpendicular = closed). Full-port ball valves have an opening the same diameter as the pipe, so they don't restrict flow. Standard ball valves cost $5–$25 at hardware stores; professional installation runs $75–$200 per valve. Every homeowner should know where their main ball valve is located and verify it turns freely at least once a year — a stuck valve during a plumbing emergency can mean thousands of dollars in water damage.

Rough-in plumbing

Rough-in plumbing is the initial phase of a plumbing installation where all water supply lines, drain-waste-vent (DWV) pipes, and gas lines are routed through the wall cavities, floor joists, and ceiling spaces of a building before drywall, flooring, and finish materials are installed. This phase occurs after framing is complete but before insulation and drywall close up the walls. During the rough-in, a plumber installs supply pipes (typically 1/2-inch and 3/4-inch copper, PEX, or CPVC for hot and cold water), drain pipes (1-1/2-inch to 4-inch ABS or PVC), and vent pipes that extend through the roof to allow air into the drainage system and prevent siphoning of traps. Stub-outs — short pipe ends capped and protruding from walls or floors — mark the connection points for future fixtures like sinks, toilets, showers, and dishwashers. The plumber must follow precise measurements for fixture placement: toilets require a 12-inch rough-in (center of drain to finished wall), shower drains must be centered in the pan footprint, and sink drains are typically 18–20 inches above the finished floor. All rough-in work must comply with the local plumbing code (typically based on the International Plumbing Code or Uniform Plumbing Code), and a municipal inspector must approve the rough-in before walls can be closed — this is called the rough-in inspection or pressure test, where supply lines are pressurized to 40–80 PSI for a set period to check for leaks, and DWV systems are tested with air or water. Failing this inspection means tearing open any sealed walls, so getting the rough-in right is critical. Costs for rough-in plumbing in new construction range from $8,000–$15,000 for a typical single-family home, or $1,500–$4,000 per bathroom in a remodel. The rough-in typically takes 2–5 days depending on home size and complexity.

Backwater valve

A backwater valve (also called a backflow prevention valve for sewer lines) is a one-way valve installed on a building's main sewer lateral to prevent sewage from flowing backward into the home during municipal sewer overloads, heavy storms, or main-line blockages. The valve contains a flap or gate that stays open during normal outflow but closes automatically when water pressure reverses. Many municipalities now require backwater valves in new construction and may offer rebates for retrofit installations. Professional installation typically costs $1,000–$3,000 and involves excavating the sewer line, cutting in the valve body, and restoring the landscaping. Some cities require a permit and inspection. Homeowners with finished basements should strongly consider installation — a single sewer backup can cause $10,000–$50,000+ in damage.

Toilet flange

A toilet flange (also called a closet flange) is a pipe fitting that connects the toilet to the drainpipe in the floor and secures the toilet to the subfloor. It consists of a ring that sits flush with or slightly above the finished floor, with a pipe collar that inserts into the drain opening. The wax ring (or modern wax-free gasket) seals between the toilet base and the flange. A damaged, cracked, or corroded flange is one of the most common causes of toilet leaks at the base — water seeps out with each flush, damaging the subfloor and promoting mold. Replacing a toilet flange costs $150–$350 professionally, though the part itself is $5–$25. If the flange sits too low after new flooring is installed, a flange extender can raise it to the correct height. Common materials include PVC (most modern homes), cast iron (older homes), and stainless steel (repair flanges that bolt over damaged originals).

Services a Plumber provides

Career transitions into Plumber

Related comparisons

Cost & pricing guides

Discover what tools and equipment you need to get started.

Licensing requirements vary by country. Explore what you need to get started.