Quick question for the code historians: on high-rise jobs we still water test stacks to 10 feet of head — where did that exact number come from, and was it ever tied to the old extra-heavy cast iron era? We just filled a 6-inch sanitary riser to 10’ on a 28-story build last week and I started wondering if the number is physics or just tradition.
a 6-inch sanitary riser to 10’ on a 28-story build last week and I started wondering Same here — legacy from hub-and-spigot days that got baked into ASTM/UPC; 10 ft is about 4.3 psi, enough to prove lead/oakum joints without blowing traps and easy to stage with test balls on high-rises. If your AHJ allows, tee in a gauge and show about 4.3 psi instead of holding a 10‑ft column on the upper floors; your inspector buy that?
My take: I’d lean toward the simplest next step and see if it changes anything this week — if not, you’ve got a clear case to escalate. What would block you from trying that?
Pretty sure the “10 feet” got set in the early ASA/National Plumbing Code era to prove lead‑and‑oakum hubs, then it just rode along into UPC/IPC and ASTM practice — a Goldilocks load that stresses joints without turning the job into a water feature. If your AHJ allows, try segmented fills or a 5‑psi air test on tall risers, especially with PVC/ABS where some listings frown on higher heads. @white21 have you ever seen a spec push beyond 10, or is it always that magic number?
I’ve always heard it was a practical “one‑story test” more than physics — easy to stage on a 28‑story and low enough that test balls don’t walk and a pop won’t flood half the core, which is why it stuck past hub-and-spigot days… @peter51 is on the history, but if you want receipts the old A40/early UPC archives here show that wording: https://codes.iapmo.org/ (, buried PDFs). Ever had an inspector ask for higher when you’ve got 6‑inch stacks running long offsets?