Workshop: pipe sizing. Episode seventy-three of the Gas Service Animated series.

Today we size a real house on the real table — the schedule-forty natural-gas table this channel verified cell by cell. Grab the method from episode five: longest length, total load per section, round the length up, never the pipe down.

Problem one. A ranch house: furnace eighty thousand, water heater forty thousand, range sixty-five thousand, dryer thirty-five thousand. The longest run, meter to the range, measures fifty-eight feet. Question: size the trunk from the meter.

Work it. Total connected load: eighty plus forty plus sixty-five plus thirty-five — two hundred twenty thousand Btu, which at roughly a thousand Btu per cubic foot is two hundred twenty cubic feet an hour. Longest length fifty-eight feet rounds up to the sixty-foot row. Now read the row: half-inch carries sixty-five. Three-quarter, one thirty-seven. One-inch, two fifty-seven. Two-twenty needs — one inch. The trunk is one-inch pipe.

Branches ride the same sixty-foot row — that's the heart of longest-length: every section uses the longest run's row with its own load. The furnace branch, eighty: needs three-quarter, since half tops out at sixty-five. Water heater, forty: half-inch works. Dryer, thirty-five: half. The range at sixty-five: half-inch carries exactly sixty-five — legal by the table, but sitting at the ceiling; a pro pencils the future and runs three-quarter.

Problem two, the upgrade trap from the tankless episode. Same house, water heater replaced with a one-ninety-nine tankless. New total: eighty plus one-ninety-nine plus sixty-five plus thirty-five — three hundred seventy-nine thousand. Does the one-inch trunk survive?

The sixty-foot row again: one-inch carries two fifty-seven — dead. Inch-and-a-quarter carries five twenty-eight — alive. The trunk must grow to inch-and-a-quarter, and the tankless branch itself, one-ninety-nine on the sixty row, also needs inch-and-a-quarter until the run shortens. One appliance swap re-sizes the artery. That's why the re-check is the law of upgrades.

The traps that fail exams and houses. Using each branch's own length instead of the longest — undersizes the far runs. Forgetting an appliance 'because it's small.' Reading the wrong pressure-drop table. And rounding length down — the table rounds up, always. The method is boring on purpose.

Check yourself with the calculator that shares this table — punch the load and the longest run, and it should land where your pencil did. The tool is for verifying judgment, not replacing it. On the exam, the pencil goes first.

Pipe sizing in one breath. Total the load, take the longest length, round up, read the row — every section on that same row with its own load. Two-twenty at sixty feet is a one-inch trunk; add a tankless and it's inch-and-a-quarter. Size the future, not just the fixture list. Next workshop: vents.