What’s a designer to do when he designs by the book, so to speak, and something fails to work as it should? That was the question posed to me a half-dozen years ago by an architect who had earlier completed a modest addition for a small rural elementary school. Working under state regulations requiring, among other things, low-flow water closets, he had dutifully incorporated a pair of these items in the plans, showing a fairly long (70-foot) branch sewer line connection to carry wastes back to the main sewer line serving the original building. What was the branch line slope? The standard 1/8-inch per foot that the National Standard Plumbing Code requires for 4-inch sanitary waste lines.

Trouble was, the line was plugging up. The architect first found out about it when he received a certified mail nasty-gram from the school board’s lawyers, documenting a six-item chronology of stoppages over the previous year and a half, with related plumber call-charges. The school board was demanding $6,000 as compensation for “poor design.” At that point, this is what we knew for sure:

1. The water closet branch line had been designed and installed with code-compliant slope-to-drain.

2. Stoppages were relatively infrequent, suggesting a cause other than a design or installation deficiency or a subsequent problem such as pipe crushing or settlement.

3. Low-flow toilets, which had just been made a requirement by the state environmental regulators, were beginning to get a lot of bad press for a number of functionality problems including the failure of downstream waste lines to clear after flushing.

4. A professional engineer had advised the architect to use a 4-inch line (3-inch would have been code-permitted) and to keep the slope to code minimum (1/8-inch per foot) to enhance the scouring effect of each flush.

We then found out that one of the classrooms served by the water closets was a special education classroom. When this class was still in the original building, some of its members had used toilet paper in remarkably creative ways with some rather interesting effects on the plumbing waste system in that location.

At this point, we had a fairly clear theoretical picture of the situation: A new technology (low-flow toilets) had crossed paths with a problematic user group—kids who found many entertaining uses for toilet paper. An institutional toilet, with higher-water-volume flush valves, would have been a better answer to the usage problem than the low-flow tank-type setups that were used. (Rationing toilet paper would have helped too.)

Armed with this information, my client went back to the school board. Unfortunately, they were not impressed. “We’ll have a professional study done,” they said, “and when we’re done we’ll add the cost to the damages we’ll collect from you.”

My recommendation was that his next step be to find out exactly what design deficiencies they planned to charge him with should the case go to court. We already knew that they hadn’t targeted the general contractor for any sub-par work by his plumbing sub-contractor, so we knew that they weren’t planning to raise claims of defective installation.

We also knew that there was no engineer to go after because, to please the school board by keeping design costs down, the architect did the plumbing layout work in schematic format, requiring shop drawings and periodic state inspections, but leaving installation details to the construction team.

It was our suspicion that the administration would have to focus their fault-finding on one or more of the following: the low-flow toilets, the size (internal diameter) of the waste line and the slope of the waste line. We also figured they wouldn’t challenge the state mandate for use of low-flow units—that would create a squabble with the state. Nor, we thought, would they challenge the marque specified—that would bring the manufacturer’s legal team into battle. We further speculated that they probably wouldn’t challenge the design’s call for a 4-inch sanitary waste line; such a call would mean challenging the plumbing code itself.

By process of elimination, we focused on waste-line slope. Did the 1/8-inch-per-foot slope meet code requirements? Yes. Did the line, nevertheless, occasionally plug up? Yes. Could the line have been installed with a steeper slope, say 1/4-inch-per-foot? Yes. Would a steeper slope have eliminated the occasional stoppage problem? Maybe. As it turned out, we were right. The administration was about to focus on what they saw as a design defect: the 1/8-inch-per-foot slope.

Normally a waste line slope change would be a horrendously expensive “repair” to execute. It would mean tearing up the carpet in the new wing, jack-hammering the floor slab and excavating the sub-slab aggregate to gain access to the waste line; resetting the waste line at a steeper slope, backfilling the excavated area, pouring new concrete and probably replacing the entire carpet.

That wasn’t the case here. The architect had incorporated in his design a floor trench in the slab for utilities, with a plywood trench cover—over which the carpet was laid. All that was needed was to peel back the carpet, lift the plywood, and there was the waste line, readily accessible for a slope change. The plumbing sub-contractor estimated the cost for a slope change at $600.

Armed with all this information, the architect instructed his attorney to draft an offer to the school board requesting permission to end the argument by proceeding with “repair” at his—the architect’s—expense. That was about three years ago. He has not yet received a reply.

If there’s a lesson here, maybe this is it: Designing “by the book” isn’t always enough. Had the case gone to court, who knows if a jury would have declined to find fault with the behavior of some special education students. And how much would it have cost the architect to present a defense? What saved his hide—and his pocketbook—was the foresight to trench the slab for utility runs, even though the architect had planned the trench for future expansion, not as a legal defense. It was fairly clear that it was the plumber’s $600 “repair” that got the school administration’s dogs off the architect’s throat.