How to Size a Gas Line — Gas Solutions Plus

Add up the load

Nameplate BTU/hr of every appliance, present and future, from the data plate or Spec Sheet — not a guess. The tables are in thousands (MBH): 364,000 BTU/hr = 364 MBH.

Measure the longest run

From the second-stage regulator to the farthest appliance, along the pipe. Use the length row at or above it. A 55 ft run uses the 60 ft row, never the 50.

Size the main — Table A

Schedule 40 at 11" WC. On your length row, read across until the capacity meets or beats the total load. That size is the main.

Size each branch on the same row

Each branch on its own appliance load, still on the longest-run row — even a 6 ft branch. That is the longest-length method, and it keeps the drop at the far end inside ½" WC.

Pick the second-stage regulator

Page 1: the smallest Marshall Excelsior unit whose rating covers the total load. 364 MBH → MEGR-1222-BAF (500,000). 600 MBH → MEGR-1622-BCF (710,000).

Tank-to-house line and first stage — Table B

PE at 10 PSIG, same total load, length from first stage to second stage. Then the first stage: MEGR-1122H-AAJ covers up to 1,000,000; the full-size 1622H models are for loads above that.

Worked example — two-stage house

Furnace 100,000 + tankless 199,000 + range 65,000364 MBH

Longest run, second stage to range60 ft → 60 ft row

Main (Table A, 60 ft): ½" 110 · ¾" 231 · 1" 434 ✓1" main

Tankless branch 199 → ¾" (231)¾"

Furnace branch 100 → ½" (110)½"

Range branch 65 → ½" (110)½"

Second stage, 364 MBHMEGR-1222-BAF

Tank to house 50 ft (Table B): ½" CTS carries 555 ✓½" CTS PE

Same line at 150 ft: ½" CTS 306 ✗ → 1" CTS 2,173 ✓1" CTS PE

First stage, 364 MBHMEGR-1122H-AAJ

Round up on length

Between rows, take the longer one. Short-cutting the row is the most common sizing error.

Don't land on the number

If the load equals a capacity (231 MBH on ¾"), go up a size. ½" WC of drop is the limit, not the target.

Future loads count

Size for the pool heater or generator the customer says is coming. Re-piping later costs more than a size up now.

2 PSI systems and the tank check

2 PSI: load and length steps are identical. House piping is sized on the 2 PSI table (far higher capacities, so ½" CSST runs most homes) with a line regulator at each appliance dropping to 11" WC. First stage to 2 PSI: MEGR-1232E-HBH or the 1622E line, page 1.

Tank vaporization: the tank must give off at least the total load as vapor. A 500 gal above-ground at 40% liquid yields roughly 360,000 BTU/hr at Florida temperatures — the example above is right at the line, so a fuller tank or a 1,000 gal is the safer call with a generator in the mix. Underground tanks and cold nights lower the yield. The Gas Load Sheet on the portal runs this check.