Skip to content 
Plumbing terms fall into four groups: the parts that carry water in, the parts that carry waste out, the valves that control flow, and the fittings that join everything together. Knowing a dozen of them turns a vague service call into an accurate one and makes an estimate far easier to read.
Key Takeaways
- A trap is the curved pipe under a fixture that holds water and blocks sewer gas.
- A vent is not a drain. It lets air in so waste can flow out.
- Supply lines carry pressurized water in. Drain, waste and vent pipes carry everything out by gravity.
- Shutoff valves at each fixture let you stop a leak without cutting water to the whole house.
- Knowing the right word for a part usually shortens the diagnosis and the invoice.
Water Supply Terms
Everything on this side of the system is under pressure. That pressure is what makes a supply leak urgent in a way a drain leak usually is not.
| Term | What It Means |
|---|---|
| Main shutoff | The valve that stops water to the entire house. Usually near the meter, in a crawlspace, or in a basement. |
| Angle stop | The small shutoff valve under a sink or behind a toilet. Also called a fixture shutoff. |
| Supply line | The flexible or rigid pipe running from an angle stop to the fixture itself. |
| PRV | Pressure reducing valve. Drops incoming street pressure to a safe household level, usually 50 to 70 PSI. |
| Expansion tank | A small tank near the water heater that absorbs pressure as heated water expands. |
| Hose bibb | The outdoor spigot. A frost free version has a long stem that closes inside the heated wall. |
If your fixtures bang when a valve closes or your toilet fill valve wears out yearly, the PRV is usually the place to look. Water pressure above 80 PSI shortens the life of everything downstream. You will also see WaterSense on fixture labels, which is the EPA efficiency certification for faucets, showerheads and toilets.
Drain, Waste and Vent Terms
Plumbers abbreviate this whole side of the system as DWV. Nothing here is pressurized. It all moves by gravity and air.
| Term | What It Means |
|---|---|
| Trap | The U or S bend under a fixture. The standing water in it blocks sewer gas from entering the room. |
| Trap arm | The horizontal pipe from the trap to the wall connection. |
| Vent stack | The pipe running up through the roof that lets air into the drain system. |
| Branch drain | The line serving one fixture or a group of fixtures before it reaches the main. |
| Main stack | The large vertical pipe collecting waste from every floor. |
| Lateral | The buried pipe from your house to the city sewer or septic tank. Usually the homeowner’s responsibility. |
| Cleanout | A capped access point that lets a plumber run a cable or camera into the line. |
A gurgling drain is nearly always a venting problem rather than a clog. Air is being pulled through the trap because it cannot get in through the vent. Our drain and sewer team checks vents before cabling for that reason.
Fittings and Pipe Terms
- Elbow: A fitting that changes direction, usually 45 or 90 degrees.
- Tee: A three way fitting where a branch joins a run.
- Coupling: Joins two pipes of the same size in a straight line.
- Reducer: Joins two pipes of different sizes.
- Union: A fitting designed to be taken apart later without cutting.
- Nipple: A short threaded length of pipe used between two fittings.
- Dielectric union: Separates copper from steel so the two metals do not corrode each other.
Pipe material names come up constantly in estimates. Copper is rigid metal, still common in Triad homes built before 2000. PEX is flexible plastic tubing used in most repipes today. PVC is white rigid plastic for drains. CPVC is cream colored and rated for hot supply. Cast iron is the heavy black drain pipe in older houses.
Water Heater Terms
- Anode rod: A sacrificial metal rod inside the tank that corrodes so the steel does not.
- Dip tube: Carries incoming cold water to the bottom of the tank so it does not mix with the hot at the top.
- T and P valve: Temperature and pressure relief valve. A safety device that opens if either climbs too high.
- First hour rating: How many gallons of hot water the unit delivers in one continuous hour.
- Recovery rate: How fast the unit reheats after the tank is drawn down.
- Sediment: Mineral buildup on the tank floor. The cause of most popping noises.
If you are replacing a unit, first hour rating matters far more than the gallon number on the label. Our water heater team sizes by demand rather than by whatever was there before.
Terms You Will Hear on an Estimate
| Term | What It Means for You |
|---|---|
| Repipe | Replacing the supply piping throughout the house, usually with PEX. |
| Hydro jetting | Clearing a drain with high pressure water instead of a cable. Removes grease that cabling leaves behind. |
| Camera inspection | Running a video camera through the line to see the actual condition. |
| Backflow preventer | A device that stops contaminated water from reversing into the clean supply. |
| Rough in | The stage where pipes are installed before walls close up. |
| Trim out | The stage where visible fixtures go on after finishes are complete. |
| Code compliant | Meeting the North Carolina State Plumbing Code as adopted locally. |
Code compliant is not a marketing phrase. North Carolina adopts a statewide plumbing code based on model standards published by IAPMO, and local inspectors enforce it on permitted work. Anything that touches a gas line, a water heater or a sewer lateral is inspected for a reason.
How to Describe a Plumbing Problem Accurately
You do not need the vocabulary to get help, but a clear description gets a truck to you with the right parts on it.
- Name the fixture. Kitchen sink, hall bath toilet, upstairs shower. Be specific about which one.
- Say what it does, not what you think is wrong. Drains slowly, drips when off, makes a sound when another fixture runs.
- Note how many fixtures are affected. One fixture points to a local issue. Several point to the main line.
- Check whether it is hot, cold or both. This narrows a supply problem immediately.
- Mention timing. Started suddenly, got worse over months, only happens after laundry.
- Look for water. Say where you see it and whether it is clean, rusty or dirty.
Rusty water at a fixture and clean water at a joint mean different things. If you are seeing water without an obvious source, our leak detection service can locate it without opening walls at random.
Frequently Asked Questions
What is a P trap and why does every fixture have one?
A P trap is the curved section of pipe under a sink or tub. It holds a small amount of standing water permanently, and that water seals the pipe against sewer gas rising into the room. A dried out trap in a rarely used bathroom is the most common source of a sewer smell.
What is the difference between a drain and a vent?
A drain carries water and waste away. A vent carries air in the opposite direction so the drain does not create a vacuum. Without a working vent, water moves slowly and traps get siphoned dry.
What does DWV stand for?
Drain, waste and vent. It is the whole non pressurized side of a plumbing system, and it is the phrase you will see on most estimates involving drainage work.
Is PEX as good as copper?
For residential supply, PEX performs well, resists freeze damage better than copper, and installs with fewer joints. Copper lasts a long time and handles heat better. Most Triad repipes today use PEX for good reasons rather than cost alone.
What is a shutoff valve and where is mine?
Individual fixture shutoffs sit under sinks and behind toilets. The main shutoff is usually where the supply enters the house, often in a crawlspace, garage or near the meter. Find yours before you need it.
What does a plumber mean by a lateral?
The lateral is the buried sewer pipe running from your house to the city main or septic tank. In most North Carolina municipalities the homeowner owns and maintains it up to the property line.
Talk to a Plumber in High Point Without the Guesswork
You should not need a glossary to get a straight answer from a contractor. We describe what we found in plain words, show you the part, and explain why the repair costs what it does before we start.
We have been doing this in the Triad since 2007, we answer the phone around the clock, and we will happily explain any term on your estimate. Our full range of plumbing services covers everything on this page.
All Star Plumbing
4003 North Main Street
High Point, NC 27265
Phone: (336) 462-1080
Hours: Open 24 hours, 7 days a week
NC Plumbing License #15130
Find us on Google Maps
Family owned since 2007, serving High Point, Greensboro, Winston-Salem and the surrounding Triad. Contact our team and describe the problem however it comes out. We will figure it out from there.
