A building subdrain serving low-level fixtures cannot discharge to the sewer by gravity. Under unamended 2021 IPC Section 712.1, how must its discharge be handled?
- AUse gravity drainage with a backwater valve as the only change
- BIncrease the gravity branch one nominal size without adding lift
- CAdd fixture traps and vents as the only change
- Discharge into a tightly covered, vented sump and lift it into the gravity drainage system by automatic pumping equipment or another approved method
Where to look it up
https://www.ncosfm.gov/b-1-2024-ncpc/open
Why D is correct
Section 712.1 addresses subdrains that cannot discharge by gravity. A backwater valve, larger pipe, traps or vents do not supply the missing lift. The rule also excludes gravity-capable building drainage from the sump in other than existing structures; do not turn that qualification into an unconditional rule for every existing building. See PDF p.115. Source: 2021 IPC base text reproduced in NC OSFM comparison document, https://www.ncosfm.gov/b-1-2024-ncpc/open