Short definition
An elbow is the basic direction-change fitting in plumbing. Standard angles are 90, 45, 22.5, and (less common) 60 degrees. Available in every pipe material — copper, PVC, ABS, CPVC, threaded steel, brass, PEX, and no-hub cast iron — and in supply (short-radius) and DWV (long-sweep) variants.
What it is
Where a run needs to turn, an elbow makes the turn. Two design conventions worth knowing:
- Short-radius elbows — used on supply piping. Compact bend, doesn’t matter that turbulence increases at the corner because pressure forces water through anyway.
- Long-sweep elbows — used on DWV. The slow, gentle bend keeps solids moving in gravity drainage. Code generally requires long-sweep 90s on horizontal-to-vertical DWV transitions.
A useful subtype is the street elbow (or street ell): a 90 with one male and one female end, eliminating the need for a separate nipple in tight spots. Common in older threaded systems where saving a fitting matters.
Why it matters to a homeowner
You’ll buy elbows for any plumbing repair that involves a direction change — a kitchen replumb, a basement bar sink rough-in, a partial repipe. The two things to match: the angle (90, 45, or what the existing layout requires) and the material/joining method (sweat copper for copper, PEX crimp for PEX, and so on). Mixing materials means using the appropriate transition fitting between two elbows of different types.
Common variants and what an elbow is not
- 90 vs. 45. Two 45-degree elbows often replace a single 90 in DWV for smoother flow.
- Long-sweep vs. short-radius. Long-sweep is for DWV (slow direction change to keep solids moving); short-radius is for supply (compact).
- Street elbow vs. standard elbow. Street has a male end on one side, eliminating a nipple in tight spots.
- Drop-ear elbow — 90 with mounting tabs for stud anchoring. Separate fitting class.