Base of the stack in a crawlspace
What's wrong here?
- Nothing. This installation is compliant
- The fitting at the base of the stack is a sanitary tee laid on its back
- The cleanout must face straight up instead of back along the pipe
- A horizontal drain must be installed dead level
Show the answer and the code reference
The answer
Nothing is wrong. The stack turns horizontal through a combination wye and 1/8 bend, the building drain has a cleanout at its upper terminal that opens in the direction of flow, and the drain falls toward the outlet.
Correct choice: 1. Nothing. This installation is compliant
UPC 706.4 allows a vertical line to enter a horizontal drain through a 45-degree wye, a combination wye and 1/8 bend, or a fitting of equivalent sweep. The combo's long branch is the tell that separates it from a sanitary tee on its back, which is not allowed. 707.4 (Minnesota is reported to amend it, but not on this point) requires a cleanout at the upper terminal of the building drain, and the plug at the end of the combo's run provides it. 707.5 allows end-of-line cleanouts to sit on the flow line as long as they open in the direction of flow. The level shows the drain falling away from the stack, as 708.1 requires. The crawlspace is tall enough to reach the cleanout and leaves well over the 18 in. of rodding room that 707.9 asks for in front of a cleanout on pipe over 2 in.
How to fix it
No correction needed. Keep the area in front of the cleanout clear so it stays usable, and keep the base of the stack supported.
Code references
UPC 2018 706.4 — Vertical to Horizontal
Vertical drainage lines connecting with horizontal drainage lines are to enter through 45-degree wye branches, combination wye and 1/8 bend branches, or other approved fittings of equivalent sweep.
Drills citing 706.4UPC 2018 707.5 — Installation
Each cleanout is to be installed so it opens to allow cleaning in the direction of flow of the soil or waste, or at right angles to it. Except for wye-branch and end-of-line cleanouts, cleanouts are to be installed vertically above the flow line of the pipe.
Drills citing 707.5UPC 2018 708.1 — Grade of Horizontal Drainage Piping
Horizontal drainage piping is to be run in practical alignment at a uniform slope of not less than 1/4 in. per ft toward the point of disposal, with 1/8 in. per ft allowed for 4 in. and larger pipe where approved.
Drills citing 708.1
Minnesota
Minnesota adopts the 2018 Uniform Plumbing Code with Minnesota amendments as the Minnesota Plumbing Code (Minn. Rules ch. 4714, effective Dec. 17, 2021). No Minnesota amendment to 706.4 is known; check ch. 4714 before relying on it. Minnesota is reported to amend 707.4 (apparently in part 4714.0707), but the reported changes are to the exceptions and urinals, not the upper-terminal cleanout this drill relies on.
About the Minnesota Plumbing CodeCitation under review. Confirm the 2018 UPC numbering and headings of 707.5 (cleanout opens in the direction of flow; wye-branch and end-of-line cleanouts exempt from sitting above the flow line) and 707.9 (12 in. clearance in front of cleanouts on 2 in. and smaller pipe, 18 in. on larger). Also confirm that Minnesota's amendment of 707.4 (apparently Minn. Rules 4714.0707) keeps the upper-terminal cleanout requirement unchanged.
Why the other choices are wrong
- The fitting at the base of the stack is a sanitary tee laid on its back. Look at the branch: it leaves the run at 45 degrees and turns up through a 1/8 bend. That is a combination wye and 1/8 bend, which 706.4 lists for a vertical-to-horizontal change of direction.
- The cleanout must face straight up instead of back along the pipe. 707.5 requires a cleanout to open so the pipe can be cleaned in the direction of flow (or at right angles), and it exempts end-of-line cleanouts from being set vertically above the flow line. This plug faces upstream, so a cable goes straight down the drain.
- A horizontal drain must be installed dead level. 708.1 requires horizontal drains to fall at least 1/4 in. per ft toward the point of disposal. A bubble resting against the upstream line is what that slope looks like on a level.