In DWV sanitary drainage, a non-fitting isn’t permitted—and here’s why sanitary tees, wye fittings, and cleanouts matter

What’s a DWV, and why should you care about fittings?

If you’ve ever watched a plumber work, you know the secret isn’t just strength or sweat. It’s flow. Drainage, Waste, and Vent systems—DWV for short—are all about moving liquid waste away from fixtures and into the main line without stubborn blockages. It’s gravity, good design, and the right fittings working in harmony. For students and pros alike, understanding which fittings belong in the sanitary drainage portion is a big deal. It keeps systems efficient, quiet, and free from clogs that cause real headaches down the line.

Sanitary drainage fittings: what actually gets used?

Let’s meet the three common players in a DWV setup and what they do. Think of them as a small team that keeps water moving where it should:

• Sanitary tee: This is the go-to for connecting a branch line to a vertical stack, or for tying a vertical waste line into a slightly offset horizontal run. The idea is to guide flow with as little turbulence as possible, so waste doesn’t swirl and settle in corners. In practice, you’ll see a sanitary tee used in places where a slight change in direction is needed while preserving a relatively straight path for the waste.

• Wye fitting: Also called a three‑way, a wye helps you split or join drainage at an angle—usually shallower than a 90-degree turn. That smoother angle reduces turbulence and “dead spots” where gunk could settle. Wyes are a staple when you’re branching off a main line to connect fixtures like sinks or toilets, and they’re especially forgiving in long runs.

• Cleanout fitting: Maintenance matters. A cleanout gives you direct access to the pipe for clearing clogs or snaking out a line. It’s like a quick-minded health check for your drainage run—an essential bit of future-proofing that saves time, mess, and money when something gets blocked.

The odd one out: why “2” isn’t a fitting at all

Now, here’s the twist many beginners bump into. In the context of a sanitary drainage portion of a DWV system, there’s a multiple-choice option that reads simply as “2.” The explanation you’ll often see is blunt: 2 isn’t a real fitting. It doesn’t correspond to a physical component you install in a pipe network. It’s not something you can, or should, place in a drain line. So, when you’re selecting the option that isn’t permitted, the correct pick is that non-fitting—what some people shorthand as “2.” It’s a reminder that not every number or label maps to a plumbing part.

A quick tour of why the other fittings fit (pun intended)

• Sanitary tees have their place, but with a caveat. They’re most appropriate where gravity can do its job smoothly, typically at a vertical-to-horizontal transition. The risk with a misoriented sanitary tee is creating a little swirl that slows drainage or invites standing water in the trap area. In many modern installations, code-conscious pros lean toward a wye plus a short elbow when a horizontal branch needs to tie in, to maintain a gentler flow path.

• Wye fittings shine when you’re branching off. They’re designed to join pipes at a shallow angle, which keeps liquids moving rather than bumping into a sharp corner. That’s why you’ll see wyes in kitchen drains and bathroom branches alike. The gradual bend minimizes turbulence and helps prevent clogs from forming at the junction.

• Cleanouts are the quiet heroes of maintenance. You might hide a cleanout behind a cabinet or in a utility area, but their accessibility is the point. A well-placed cleanout means you can clear a stubborn clog from the source, not tear apart walls or floors to get to the blockage. They’re simple, robust, and invaluable when something stubborn crops up.

Some practical notes you’ll actually use on the job

• Orientation matters, but not every fixture’s fate hinges on a single correct angle. When you’re choosing between a sanitary tee and a wye, think about the flow direction, the ease of cleaning, and how future cleanouts could fit into the route. In many builds, you’ll find a deliberate preference for wyes in branching lines to keep things flowing without dead zones.

• Cleanouts need to be accessible. If you’re planning a layout, think practical access during maintenance. A tidy run behind a wall is great for aesthetics, but a cleanout that’s hard to reach defeats the purpose. It’s a balancing act between clean looks and practical serviceability.

• Materials matter, too. In residential DWV work, PVC is common in many regions, while ABS might be used in others. Fittings are designed to mate with those materials, with appropriate solvent welds or mechanical couplings. Brands you’ll encounter include names like Oatey, Zurn, and Spears, which produce both the pipes and the fittings that hold a system together. The goal isn’t flash; it’s reliability and ease of maintenance.

• Codes aren’t guesswork. They exist so that a system behaves well under normal use, resists clogging, and remains safe from sewer gases. The exact permitted fittings and configurations can vary by jurisdiction and code edition. As you work, you’ll hear terms like “venting” and “slope” sprinkled into the conversation. The vent portion of DWV is about letting air in and out so traps don’t siphon dry. A well-vented system moves waste more predictably and protects the upright stack from pressure imbalances.

A few tangents that connect to the main idea

• Venting isn’t optional. If a system drains like a clogged dam, a vent could be the missing piece. Without proper venting, you can end up with slow drains and gurgling sounds as air gets trapped. So, even though most of our focus here is on the physical fittings, keep venting in the back of your mind as the partner in crime that keeps everything from stalling.

• The “no dead space” rule. In drainage, dead spaces—areas where the water can linger—are trouble. That’s part of why the shape of fittings matters. A properly chosen wye or a carefully placed sanitary tee helps maintain a smooth flow and reduce places where solids might settle. It’s not just about moving water; it’s about keeping the line clean over time.

• Maintenance matters, too. You’ll find that a smart layout reduces clogging risk, but you’ll still need to service lines from time to time. Cleanouts aren’t a luxury; they’re an investment in the long-term health of the system. If you’ve ever wrestled with a stubborn clog, you know the relief a cleanout can bring.

Putting it all together: a simple way to remember

• In the sanitary drainage portion, the fittings you typically rely on are sanitary tees (for certain vertical-to-horizontal transitions), wye fittings (for gentle branch connections), and cleanouts (for access and cleaning).

• The non-fitting “2” is not a real component at all, so it isn’t something you’d install in the DWV path. It’s a reminder to stay precise about what’s a part and what isn’t.

• When in doubt, think about flow, access, and code compliance. If a choice seems to introduce turbulence, create a maintenance headache, or violate local rules, it’s probably not the right pick.

A practical mindset for real-world plumbing

• Plan with your eyes on the end result: a system that drains smoothly, reduces the chance of clogs, and stays serviceable for years. That means favoring fittings that encourage straight, low-turbulence flow in the main run and keeping cleanouts accessible.

• Don’t gloss over orientation. A slight misalignment can change how the liquid and solids behave downstream. Always verify that the chosen fittings match the intended direction of flow.

• Stay curious about materials and tools. You’ll encounter PVC, ABS, traps, couplings, and a toolbox full of cement, primers, and connectors. Brands like Oatey or Fernco offer the hardware you’ll need, and having the right tools on hand makes the job feel that much more straightforward.

A closing thought

If you’re parsing through questions about DWV fittings, you’re training your eye to spot the subtle differences that matter in real life. It’s not just about memorizing names; it’s about recognizing how each piece influences flow, maintenance, and safety. Sanitary tees, wyes, and cleanouts each have a job to do, and they do it best when placed with intent. The “2” might be a tempting answer in a quiz, but in the world of drainage, it isn’t a part you’ll ever fit into a sanitary drainage run.

So next time you’re sketching a layout, imagine the water’s journey—down, across, then up just enough to meet the vent, with a cleanout waiting nearby for the moment you’ll need it. That’s the rhythm of a well-designed DWV system: practical, dependable, and a little bit elegant in its simplicity.