We use essential local storage for app functionality, optional analytics (Google Analytics), and error monitoring with session replay (Sentry). No traditional cookies. Privacy Policy
Size a single section of gas pipe by the longest-length method (IFGC 2021 §402.4). Enter the section's total downstream BTU/hr load and the developed length to the farthest outlet from the meter. Undersized gas piping is a life-safety risk — verify against the code edition adopted in your jurisdiction.
Size a single section of gas pipe by the longest-length method (IFGC 2021 §402.4). Enter the section's total downstream BTU/hr load and the developed length to the farthest outlet from the meter. Undersized gas piping is a life-safety risk — verify against the code edition adopted in your jurisdiction.
Gas work is life-safety work.
Leak-test every joint (soap solution or electronic detector) before restoring service, confirm adequate combustion air per IFGC §304, and never operate gas appliances in a space without working CO detection. Gas leaks and CO are fatal — when in doubt, stop and call a licensed gas fitter.
Most common residential black-iron / galvanized steel pipe. Sizes in nominal inches. Conditions: ≤ 0.5 psi inlet, 0.5″ w.c. drop, 0.60 sg natural gas.
Gas systems sized incorrectly can cause fire, explosion, electrocution, or carbon monoxide poisoning. Results are estimates only and must be reviewed by a licensed professional before any work is performed. Do not install based on these results alone. Read full terms.
For 199 MBH at 30 ft of developed length, NFPA 54 Table 6.2(1) calls for 1" Schedule 40 black iron. At 60 ft, you go to 1-1/4". Always check the tankless manufacturer's minimum gas pressure and inlet size — that often dictates pipe size more than the table.
Yes — CSST (corrugated stainless steel tubing) is permitted by NFPA 54 when installed per the manufacturer's listing and bonded per NEC 250.104(B). CSST uses different capacity tables than black iron, so always use the manufacturer's sizing chart for the specific brand.
For 2-PSI or less systems, 0.5" W.C. pressure drop is typical. For 2-PSI systems with a regulator at the appliance, larger drops (1.0" W.C. or 1.0 PSI on the high side) are allowed. The calculator defaults to 0.5" W.C., the most common residential design pressure drop.