11.4 Spotting Code Violations on Waste and Vent Drawings: A Checklist with Code Citations
Key Takeaways
A sanitary tee may be used only for horizontal-to-vertical connections; horizontal-to-horizontal and vertical-to-horizontal turns need wyes or combination wye and one-eighth bends (UPC 706).
A water closet on 2-inch pipe, or more than three water closets on a 3-inch horizontal drain, violates Table 703.2 notes 3 and 4.
A trap arm longer than Table 1002.2 allows, or a water closet more than 6 feet from its vent, is a violation.
A vent taken off below the trap weir (except for water closets), or from the bottom of a horizontal drain, violates UPC 905.2 and 905.5.
Washington requires cleanouts at the upper terminal, every 100 feet, and for turns totaling more than 135 degrees, with 12 or 18 inches of clearance (WA 707.4, 707.9).
Why Violation Questions Appear
L&I's Part 2 description centers on sizing, but a drawing that shows fixtures, piping, vents, and cleanouts also lets the exam ask whether a connection or arrangement is legal. The rules are the same ones you use for Part 1, applied to a picture. Work through the drawing with this checklist.
Fittings and Changes of Direction
| Look for | Violation | Code |
|---|---|---|
| Sanitary tee joining two horizontal lines | Must be a wye or combination wye and 1/8 bend | 706.3 |
| Vertical line dropping into a horizontal drain through a sanitary tee | Same requirement | 706.4 |
| Double sanitary tee whose barrel is not two sizes larger than its largest inlet | Prohibited | 706.2 |
| Double hub, tapped tee, side inlet quarter bend, running thread, band, or saddle used as a drainage fitting | Prohibited | 310.1 |
| Any waste connected to a closet bend or water closet stub | Prohibited | 310.3 |
| Drain or vent drilled and tapped for a connection | Prohibited | 310.2 |
| Drain reduced in size in the direction of flow | Obstructs flow | 310.5 |
Sizing
| Look for | Violation | Code |
|---|---|---|
| Water closet on 2-inch drain | No water closets on 2-inch pipe | Table 703.2 note 3 |
| Four or more water closets on a 3-inch horizontal drain | Limit 3 (Washington exception only for single-family additions or alterations with AHJ approval) | Table 703.2 note 4 |
| Five or more water closets on a 3-inch vertical stack | Limit 4 | Table 703.2 note 4 |
| Two or more DFU on a 1-1/2-inch horizontal drain | Limit 1 DFU | Table 703.2 |
| A 1-1/2-inch drain on a kitchen sink, dishwasher, or urinal where a 2-inch drain is required | Minimum 2-inch drain | Table 702.1 note 2 |
| A 1-1/2-inch trap on a shower | Showers need a 2-inch trap and waste outlet (WA exception only for a tub-to-shower replacement with AHJ approval) | Table 702.1; WA 408.4 |
| Slope of 1/8 inch per foot on 3-inch pipe | Only 4-inch and larger, with AHJ approval | 708.1 |
Traps
| Look for | Violation | Code |
|---|---|---|
| S-trap, bell trap, crown-vented trap, or a trap with movable parts | Prohibited | 1004.1, 1004.2 |
| Two traps in series on one fixture (double trapping) | Prohibited | 1004.1 |
| Fixture tailpiece longer than 24 inches | Prohibited | 1001.2 |
| Trap arm longer than Table 1002.2 (30, 42, 60, 72, or 120 inches for 1-1/4 through 4-inch arms) | Too long | 1002.2 |
| Water closet more than 6 feet from its vent, measured from the top of the flange | Too long | Table 1002.2 note 2 |
| Trap larger than one pipe size over Table 702.1, or not the same size as its trap arm | Prohibited | 1003.3 |
| Clothes washer trap below the floor, or a standpipe under 18 or over 30 inches | Prohibited | 804.1 |
Vents
| Look for | Violation | Code |
|---|---|---|
| Vent taken off the bottom of a horizontal drain, or below its centerline | Must be above the centerline | 905.2 |
| Vent opening below the trap weir (other than water closets) | Acts like a crown vent | 905.5, 1002.4 |
| Vent turning horizontal below 6 inches above the flood-level rim without drainage fittings and grade | Violation | 905.3 |
| Vent with sags or pockets | Must drip back to the drain | 905.1 |
| Individual vent smaller than half the drain, or smaller than 1-1/4 inches | Undersized | 904.1 |
| Vents through the roof whose total area is less than the required building sewer | Aggregate venting fails | 904.1 |
| Vent reduced in size through the roof | Must be undiminished | 905.4 |
| Vent terminal within 10 feet of a window or air intake and not 3 feet above it, or less than 6 inches above the roof | Termination | 906.1, 906.2 |
| A branch with no vent at all (single-stack, unvented branch) | Prohibited | 310.4 |
| Restaurant kitchen equipment on a circuit-vented branch | Washington prohibition | WA 911.1 |
Cleanouts (Washington 707)
| Look for | Violation | Code |
|---|---|---|
| No cleanout at the upper terminal of a horizontal drain (unless an exception applies) | Missing | WA 707.4 |
| Horizontal run over 100 feet with no intermediate cleanout | One required per 100 feet or fraction | WA 707.4 |
| Horizontal turns totaling more than 135 degrees without an added cleanout | Missing | WA 707.4 |
| Branch shorter than 5 feet serving a sink or urinal with no cleanout | Exception 1 does not apply | WA 707.4 |
| Less than 12 inches in front of a 2-inch cleanout, or 18 inches for larger | Clearance | WA 707.9 |
| Undersized cleanout plug | Table 707.1 sizes | 707.10 |
Other Items
- Fixtures below the next upstream manhole cover with no backwater valve (710.1).
- Drainage connections within 8 feet of the base of a suds-producing stack serving three or more stories (711.1).
- Ejector discharge entering a horizontal drain from the side instead of from the top through a wye (710.4).
- A dishwasher tied into the discharge side of a disposer (419.2).
Practice: Find the Four Violations
A drawing shows a second-floor restroom. A 2-inch horizontal branch carries two lavatories and a floor drain, then a water closet connects to the same 2-inch branch. A sanitary tee joins that branch to a 3-inch horizontal main. The floor drain's 2-inch trap arm runs 6 feet to its vent. The lavatory vents rise 3 inches above the lavatory rims, then run horizontally to the branch vent.
Answers:
- The water closet on the 2-inch branch violates note 3. The branch must be 3 inches from the closet connection downstream.
- The sanitary tee joining two horizontal lines violates 706.3. Use a wye or combination wye and 1/8 bend.
- A 6-foot (72-inch) trap arm on a 2-inch floor drain exceeds the 60-inch limit in Table 1002.2.
- The lavatory vents turn horizontal only 3 inches above the rims, which violates 905.3. They must rise 6 inches above the flood-level rim, or be installed with drainage fittings and grade.
A drawing shows a horizontal 3-inch branch joining a horizontal 4-inch building drain through a sanitary tee. What is the violation?
The tee must be a double sanitary tee
None; sanitary tees are allowed for all changes of direction
Horizontal-to-horizontal connections must use a 45-degree wye, a combination wye and one-eighth bend, or equivalent sweep (UPC 706.3)
The branch must be 4 inches
A lavatory's vent is taken off the bottom of its horizontal waste line. Which UPC section does this violate?
707.4, because a cleanout is required
905.2, because the vent invert must be above the centerline of the horizontal drain
906.1, because the vent must terminate 6 inches above the roof
1005.1, because the trap seal must be 2 to 4 inches
A drawing shows a water closet on a 4-inch fixture drain that runs 8 feet from the top of the closet flange to the inner edge of its vent. What is the violation?
The fixture drain must be 3 inches
Water closets may not be vented
None, because 4-inch trap arms may be 120 inches long
The developed length exceeds the 6-foot limit for water closets in Table 1002.2 note 2
Sections you finish are checked off in the contents.