Use a sanitary tee only where a horizontal branch drops into a vertical stack. For horizontal runs and where a stack turns horizontal, use a wye, a combination wye and 1/8 bend, or a long-sweep bend; that is what IRC Table P3005.1 allows. The fitting shape decides which way waste can flow, so the direction matters more than the size.
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This guide covers the common PVC and ABS drain, waste and vent fittings and the 2024 IRC rules for each.
Which fitting goes which direction
| Fitting | Horizontal to vertical | Vertical to horizontal | Horizontal to horizontal |
|---|---|---|---|
| Sanitary tee | Yes (multiple-connection limits apply) | No | No |
| Wye | Yes | Yes | Yes |
| Combination wye and 1/8 bend | Yes | Yes | Yes |
| Long sweep | Yes | Yes | Yes |
| 1/16, 1/8 and 1/6 bends | Yes | Yes | Yes |
| Quarter bend | Yes | Only on a 2-inch or smaller fixture drain | Only on a 2-inch or smaller fixture drain |
This is the table in Section P3005.1 of the 2024 International Residential Code (codes-conv.iccsafe.org). It says changes in direction in drainage piping are made with sanitary tees, wyes, sweeps and bends used according to the pattern of flow. Your state or city may use another code or edition, so check the local version before the inspection.
Short sweeps also appear in the table with footnoted limits; read the footnotes for your pipe size before using one where flow turns horizontal.
Sanitary tee: only where flow drops into a vertical pipe
A sanitary tee has a curved branch that turns flow downward. That curve works when a horizontal branch, like a sink or tub drain, enters a vertical stack. The IRC table allows it only in that horizontal-to-vertical direction.
The curve is shaped to turn flow downward. The table marks it as not allowed for vertical-to-horizontal or horizontal-to-horizontal changes, so do not lay one on its back in a horizontal run; use a wye or combination fitting there.
Choose the Charlotte PVC 00400 4-inch sanitary tee for a 4-inch stack connection. Charlotte’s DWV catalog (charlottepipe.com) lists part 400 as an all-hub sanitary tee. On October 15, 2026, the standard new offer from a third-party seller showed limited stock with part PVC 00400 and UPC 611942034666.
Check Charlotte PVC 00400 4-inch sanitary tee on Amazon →
Wye and combination wye: for horizontal runs
A wye joins a branch at 45 degrees, so waste merges with the main flow instead of hitting it. The IRC table allows wyes in all three directions, which makes them the standard fitting for horizontal drains and for where a stack turns into a building drain.
A combination wye and 1/8 bend (often called a combo) is a wye with the branch already turned to 90 degrees. Use it where a horizontal branch joins a horizontal main and needs to end up perpendicular. The IRC table allows it in all directions too.
Choose the Charlotte PVC 00600 3-inch wye for a 3-inch horizontal line. Charlotte’s catalog lists part 600 as a 45° all-hub wye, and part 501 as the one-piece combination wye and 1/8 bend. On October 15, 2026, the 00600’s standard new offer from a third-party seller showed stock with UPC 611942036097.
Check Charlotte PVC 00600 3-inch wye on Amazon →
Bends: long sweep, quarter bend and street fittings
Bends are named by fractions of a circle: a 1/4 bend turns 90 degrees, a 1/8 bend turns 45, a 1/16 bend turns 22-1/2, and a 1/6 bend turns 60. Long-sweep quarter bends have a bigger radius than standard quarter bends.
Under the IRC table, a long sweep works in every direction, while a standard quarter bend is limited to horizontal-to-vertical except on a 2-inch or smaller fixture drain. When a stack turns into a horizontal drain at the bottom, use a long sweep or two 1/8 bends.
A street fitting has one spigot end that glues straight into another fitting’s hub, which saves a short piece of pipe in tight spots. Choose the Charlotte PVC 00309 3-inch long-sweep 1/4 bend, street, which Charlotte’s catalog lists as hub × spigot. On October 15, 2026, its standard new offer from a third-party seller showed limited stock with part PVC 00309.
Check Charlotte PVC 00309 3-inch long-sweep street bend on Amazon →
Closet bend: the toilet connection
A closet bend is the 90-degree fitting under a toilet that connects the closet flange to the drain. IRC P3005.1.4 accepts 3-inch quarter bends for a water closet connection provided a 4 × 3-inch flange receives the toilet horn; alternately, a 4 × 3-inch elbow is acceptable with a 4-inch flange.
Choose the Charlotte PVC 00330 3 × 4-inch reducing closet bend when the flange is 4 inches and the drain is 3. Charlotte’s catalog lists part 330 as a reducing closet bend, hub × spigot. On October 15, 2026, the standard new offer from a third-party seller showed stock with part PVC 00330.
Our toilet rough-in guide covers where the bend and flange need to land.
Check Charlotte PVC 00330 3×4 closet bend on Amazon →
Double sanitary tee and double wye
A double sanitary tee (sanitary cross) connects two opposing horizontal branches to a stack, such as back-to-back sinks. IRC P3005.1.1 allows it when the opposing connections are the same size and serve similar fixtures.
The same section says a double sanitary tee pattern must not receive back-to-back water closets, or fixtures with pumping action, unless the horizontal length from the toilet outlet to the fitting is at least 18 inches. For back-to-back toilets closer than that, use a fitting the table allows, such as a double combination wye and 1/8 bend, and confirm the layout with your inspector.
Choose the Charlotte PVC 00428 3-inch double sanitary tee for back-to-back lavatories or similar fixtures. Charlotte’s catalog lists part 428 as an all-hub double sanitary tee (sanitary cross). On October 15, 2026, its standard new offer from a third-party seller showed stock with part PVC 00428.
Check Charlotte PVC 00428 3-inch double sanitary tee on Amazon →
PVC or ABS: same shapes, different cement
ABS (black) DWV fittings come in the same patterns as PVC: sanitary tees, wyes and quarter and eighth bends. Charlotte’s catalog lists PVC and ABS versions side by side for most part numbers.
The difference is the joint. ABS uses ABS cement, PVC uses PVC primer and cement, and joining the two needs a transition cement or coupling your local code allows. Match new fittings to the pipe you have. Our PVC vs ABS guide explains where each is used.
Before you glue anything
Dry-fit the whole run first, mark alignment lines across each joint, and check that every branch fitting points the way the flow will go. A wye glued backward drains against the flow.
Keep the right slope on horizontal drains and make sure each fixture is vented. Our trap arm length guide and wet venting guide cover those rules.
Test the finished system before covering it. Our DWV testing guide covers the water test.
Frequently asked questions
When can I use a sanitary tee?
Under the IRC, only where flow changes from horizontal to vertical, such as a horizontal branch entering a vertical stack.
Can a sanitary tee be used on its back?
No. The IRC table does not allow a sanitary tee for horizontal-to-horizontal or vertical-to-horizontal changes. Use a wye or combination wye and 1/8 bend.
What fitting goes at the bottom of a stack?
A long sweep or two 1/8 bends. A standard quarter bend is only allowed there on a 2-inch or smaller fixture drain.
Can back-to-back toilets share a double sanitary tee?
Not unless the horizontal length from each toilet outlet to the fitting is at least 18 inches, per IRC P3005.1.1.
Are PVC and ABS DWV fittings interchangeable?
The shapes match, but the materials need different cements. Joining them needs a transition cement or coupling your local code allows.
How we chose
This document-based guide makes no hands-on testing claim. We read Section P3005 and Table P3005.1 of the 2024 IRC and Charlotte Pipe’s PVC and ABS DWV dimension catalog, and linked only listings whose PVC part numbers match that catalog. On October 15, 2026, all five linked standard new offers showed stock. Read our selection method and about Plumbing Picks.
Primary sources
- 2024 IRC Chapter 30, Section P3005 (codes-conv.iccsafe.org): Table P3005.1 fittings for change in direction; P3005.1.1 multiple connections; P3005.1.4 water closet connection. Model code; local adoption varies.
- Charlotte Pipe PVC and ABS DWV dimension catalog (charlottepipe.com): parts 309, 330, 400, 428, 501, 600.