Plumbing: How Water Gets In and Out of a House

What this course is

Written for teens and adults with no plumbing experience. It picks up where the house guides in Being an Adult 101 leave off. Each lesson explains the “why” as well as the “what”: why a foot of water adds 0.433 psi, why a 2-inch trap seal needs a vent, why freezing water splits pipes, why a tankless heater needs so much power. Facts and numbers come from U.S. government agencies such as EPA, CDC, DOE, HUD, CPSC, USGS and BLS, from university extension programs and OpenStax textbooks, and every lesson lists its sources.

How to use it

1. Start with Lesson 1 for the big picture, then go in order or jump to the part of the house you’re curious about.
2. Each lesson has labeled diagrams, a parts table where it fits, a short quiz and links to go deeper. Badges show the level.
3. Play with the interactive pieces: the pressure tower, the trap and vent, the animated toilet, the water heater and the leak counter.
4. Use the troubleshooting finder when something seems wrong, and climb the skill ladder one rung at a time.

Map of the house

Every system, drawn inside one house. Switch between the water supply and the drains and vents. Point at a system or its name to see what it does; click to open its lesson.

The lessons

1. 1 🗺️ The Big PictureWater comes in under pressure and leaves by gravity: a map of a house’s plumbing. Beginner6 min✓ Done
2. 2 💧 Water Supply: From the Street to the FaucetThe service line, meter and main shutoff; where water pressure comes from; pressure-reducing valves, pipe sizes, water hammer and backflow. Beginner11 min✓ Done
3. 3 ⤵️ Drains, Traps and VentsGravity and slope, the trap’s water seal, why vents keep traps from siphoning, cleanouts, the building sewer and septic systems. Beginner11 min✓ Done
4. 4 🚽 Fixtures and How They WorkToilets and the siphon flush, faucet valves, anti-scald shower valves, sinks and tubs, and washer and dishwasher hookups. Beginner10 min✓ Done
5. 5 ♨️ Water HeatersTank heaters part by part, the temperature-and-pressure relief valve, what temperature to use, sediment, tankless and heat pump heaters. Intermediate13 min✓ Done
6. 6 🔩 Pipes, Fittings and JoiningCopper, PEX, CPVC, PVC, ABS, cast iron and galvanized steel; how soldered, threaded, solvent-welded, crimped and push-fit joints work; lead-free rules. Intermediate7 min✓ Done
7. 7 🧪 Water Quality and SafetyLead and lead service lines, testing private wells, hard water and softeners, certified filters, germs that grow in plumbing, and cross-connections. Intermediate7 min✓ Done
8. 8 💸 Leaks and Water UseHow much leaks waste, the two-hour meter test and the toilet dye test, finding hidden leaks, and reading your water bill. Beginner7 min✓ Done
9. 9 🧊 Clogs, Frozen Pipes and Noisy PipesWhy drains clog and how plungers and snakes clear them, why pipes burst in the cold, low pressure, and water hammer. Beginner6 min✓ Done
10. 10 🔥 Gas Piping and Gas AppliancesHow natural gas and propane reach appliances, shutoff valves and connectors, venting and carbon monoxide, why gas work is licensed, and what to do if you smell gas. Advanced7 min✓ Done
11. 11 🔎 Troubleshooting by SymptomAn interactive finder: pick a symptom, answer a question, and get likely causes, safe checks and when to call a plumber. Beginner5 min✓ Done
12. 12 🧰 Doing Your Own WorkA starter tool kit, shutting off the water first, permits and inspections, what homeowners commonly do, and the skill ladder. Beginner5 min✓ Done
13. 13 🧑‍🔧 Careers in PlumbingWhat plumbers, pipefitters and steamfitters do, how apprenticeships and licenses work, and current pay and job outlook from BLS. Beginner4 min✓ Done

Troubleshooting finder

Something seems wrong? Pick a symptom, answer a question, and see the likely causes, what you can safely check, and when to call a plumber. Lesson 11 explains how to think it through.

The skill ladder

Build skill one rung at a time, with an experienced helper and the manufacturer’s instructions the first time you do anything new. Lesson 12 covers tools, shutting off the water and permits.

1. 1

   First jobs

   No tools beyond a plunger, a flashlight and food coloring.

   • Find and test your main shutoff valve
   • Find every fixture shutoff valve
   • Unclog a sink or toilet with a plunger
   • Do the toilet dye test and the two-hour meter test
   • Fix a running toilet: chain, float and flapper
   • Clean faucet aerators and showerhead scale
   • Refill a dry trap in an unused drain
   • Check hot water temperature with a kitchen thermometer
   • Test your smoke and CO alarms
2. 2

   Next steps

   Basic hand tools, the manufacturer’s instructions, and an experienced helper the first time.

   • Clear a clog with a hand drain snake
   • Replace a showerhead, using thread tape
   • Replace a toilet fill valve
   • Replace a faucet washer or cartridge (match the old part)
   • Check your water pressure with a gauge
   • Insulate exposed pipes in cold spaces
   • Add a hose-bibb vacuum breaker
3. 3

   Intermediate jobs

   More tools, a mentor, and a check on whether your town needs a permit. Mistakes here can flood a house.

   • Replace a faucet
   • Replace a toilet
   • Replace a sink trap or a fixture supply line
   • Replace a fixture shutoff valve
   • Install a washing machine or dishwasher hookup
   • Flush a water heater, following its manual
4. 4

   Leave these to licensed pros

   They need a license, a permit, special training or equipment.

   • Gas piping, gas connectors and gas appliance hookups (CPSC: only a qualified professional)
   • Installing or replacing a water heater, and its venting and T&P discharge piping
   • The water service line, meter and curb valve, and any lead service line
   • Moving or adding drains, vents and supply lines inside walls
   • Main sewer line repairs, and septic system service
   • Pressure-reducing valves and backflow assemblies where your code requires a licensed installer
   • Soldering and any work with an open flame in walls

Careers

Plumbers install and repair water, gas and other piping systems in homes, businesses and factories. Here are the U.S. Bureau of Labor Statistics figures for plumbers, pipefitters and steamfitters from its Occupational Outlook Handbook (page last modified August 27, 2026):

Most plumbers learn through a paid apprenticeship of 4 or 5 years, then pass a licensing exam to become journey-level; master plumbers need more experience and another exam. Lesson 13 has the details, the training paths and how licensing works.

Sources

Each lesson lists the sources for its own facts. Here they all are in one place.