6.2 Part II Practical Gas Piping

6.2 Part II Practical Gas Piping

Quick Answer: Part II is closed book, 40 items, 160 minutes, 70 percent, scored on its own (PSI CIB dated October 3, 2025). Gas Piping is 7 of those 40. Bring only a non-programmable calculator. On an isometric you measure developed length along the pipe, convert nameplates to CFH, put downstream load on each segment, and enter the longest-length column of the correct table excerpt (or apply that method when the item asks which length or load is correct). Then hunt the drawing for CSST versus steel, regulator location, underground notes, and drip / sediment-trap details.

Part I already tested whether you know 248 CMR 4.00/5.00. Part II tests whether you can read a job. The seven gas-piping items sit beside 20 isometric-analysis items and 8 gas-venting items. A gas isometric can feed more than one subject area. This section stays on piping. Appliance vents are Section 6.3. 248 CMR 10.16 DWV vents are a different chapter.

What the room allows — and what it does not

The CIB security list is blunt. Calculator: only non-programmable, non-printing, silent, battery-operated, non-alphabet keys. No phone. No programmable engineering calculator. No printed NFPA 54 in the booth — 248 CMR 3, 4, 5, 7, 10, 11; NFPA 54-2012; NFPA 58-2011; and M.G.L. c. 142 are not allowed in the examination center. Scrap paper is PSI’s. Passing is a minimum of 70 percent on each part. Fail Part II and you retake Part II only; that passing score is valid one year.

Because the book is outside, practical piping items usually do one of three things:

1. Ask a method question (which length column, which load, which material is illegal on the drawing).
2. Print a small capacity excerpt and expect you to apply longest-length plus downstream CFH.
3. Ask you to identify a symbol or a note (CSST, PE with tracer, regulator vent, drip).

You are not expected to have memorized every Annex C cell. You are expected to remember the walk from Section 2.2: gas identity, CFH = BTU/h ÷ heating value (natural gas often ÷ 1,000), longest developed length to the most remote outlet as the one length column, downstream-only load on each piece, first published capacity ≥ that load, Massachusetts 0.5 PSIG / 14 inch water column default, CSST capped at 14 inch WC, no galvanized pipe, no CSST on an exterior meter.

How to read the gas isometric (order of operations)

Treat the drawing like a trench walk, not like a pretty picture.

1. Find the point of delivery. Natural gas: meter outlet (or the service regulator/shutoff outlet if there is no meter) per 248 CMR 4.03. Propane: supply or the outlet of the first regulator at the tank, then watch where the second-stage regulator sits on the building.
2. Trace every offset. Developed length is the pipe you would cut: drops, rises, 90s, the 3-foot foundation stub, the 6-foot drop to the furnace. A scale bar across a basement plan under-counts.
3. Mark the most remote appliance. That path’s length is the column for every segment under the longest-length method, including short water-heater branches.
4. List nameplates, convert to CFH, and write the downstream total on each segment. After a tee, the branch carries only what it still serves.
5. Read the notes block before you pick a size: fuel, pressure, CSST manufacturer, underground cover, “test before backfill,” drip at low point, sediment trap at appliance.
6. Identify the tubing. Straight heavy line with threaded fittings = steel. Corrugated / wavy / “CSST” callout after a termination fitting = CSST. Yellow jacket notes are a hint, not a license to land CSST on the outdoor meter.

Regulator location on a drawing. A utility service regulator at the meter set is usually upstream of your permit piping. An appliance regulator (or pounds-to-inches regulator the plumber installs) sits upstream of the equipment it protects, with the vent piped to a safe outdoor point per NFPA 54 and 248 CMR 5.09 (CSST regulator-vent lines still cannot punch a roof or sidewall — transition to steel at least one foot inside). LP two-stage: first stage at the tank, second stage on the building; 248 CMR 5.05(4)(B)5.a does not demand a PE solely for the elevated piping between those two when the second stage is outside. Interior building piping is still the low-pressure default unless the elevated-pressure engineer path applies.

Drip legs versus sediment traps. A drip (sometimes drawn as a tee with a capped nipple at a low point of a long run) collects condensate in the piping. An appliance sediment trap is downstream of the appliance shutoff, as close as practical to the inlet, typically a tee with the capped nipple in the bottom opening of the run (NFPA 54-2012 9.6.7, not rewritten by 248 CMR 5.09). Furnaces, boilers, and water heaters want that trap. Illuminating appliances, ranges, clothes dryers, decorative fireplaces, and outdoor cooking appliances are the usual exceptions. Do not skip the furnace trap because you already drew a drip at the meter.

Underground notes. Look for burial depth, sleeve, tracer, warning tape, and “open-trench test.” Ordinary NFPA 54 cover is 12 inches (18 inches where damage is likely). Massachusetts CSST in contact with earth is 18 inches from top of grade, warning tape no more than 6 inches from grade, sleeve liquid-tight. 248 CMR 5.08: test in the inspector’s presence before any portion is enclosed or covered. Undiluted LP does not ride the vented under-building conduit of 248 CMR 5.07(1).

Worked isometric 1 — developed length, loads, and the table column

Drawing (described). Exterior natural-gas meter on the left foundation wall. Steel through the wall, 3 feet into the basement to an interior shutoff and union. From that shutoff the main runs 8 feet to Tee R (range branch). The range branch is 15 feet of steel to a 65,000 BTU/h domestic range (no sediment trap — range exception). After Tee R the main runs 14 feet to Tee WH. The water-heater branch drops 4 feet then runs 9 feet to a 40,000 BTU/h tank-type heater; the isometric shows a tee-and-cap sediment trap at the heater inlet after the shutoff. After Tee WH the main runs 18 feet to Tee D. The dryer branch runs 7 feet horizontally and drops 3 feet to a 35,000 BTU/h dryer. After Tee D the main runs 14 feet then drops 6 feet to an 80,000 BTU/h furnace with a sediment trap after the shutoff. Notes: low pressure, 0.5 PSIG / 14 inch WC, approximate 1,000 BTU/cu ft.

Developed lengths (include the 3-foot stub):

Longest length = 63 feet. That is the column for the range branch, the water-heater branch, and every trunk piece. Do not size the 26-foot range run from a 26-foot column.

CFH (÷ 1,000): range 65, water heater 40, dryer 35, furnace 80. Total 220 CFH.

If the item prints a natural-gas, 0.60 specific-gravity, low-pressure steel excerpt, stay in the 63-foot column (or the next longer listed length if 63 is not printed). Read down until capacity is ≥ 220 for the first trunk, ≥ 65 for the range, and so on. First size that meets or exceeds the load is the answer — not a memorized “one-inch house.”

Calculator use. Add the stub and the drops on scrap paper. 3 + 8 + 14 + 18 + 14 + 6 is easy to mis-key if you skip the last drop. The non-programmable calculator is for the arithmetic, not for storing a crib sheet of table cells.

Worked isometric 2 — CSST versus steel on the same sheet

Drawing (described). Same four appliances. The meter is outdoors. A note says “CSST interior after termination fitting.” The elevation shows straight steel from the meter, clamped to the foundation, through a termination fitting at the wall, then a corrugated line with manufacturer fittings to a manifold in the basement. A wavy line continues to the furnace, staying strapped to the joists; the last 24 inches to the furnace shutoff is still CSST with a gas cock at the appliance. A distractor callout shows a second corrugated whip from the meter spud to a generator.

Read it this way. 248 CMR 5.05(8)(e): no CSST on the exterior meter. The legal path is steel, rigid, to the building, termination fitting, then CSST inside. The generator whip off the meter spud is the fail. CSST is not the yellow appliance connector downstream of the shutoff (5.05(8)(k)). Size the CSST from that manufacturer’s EHD table at not more than 14 inch WC. If the drawing also shows a #6 bonding jumper note, remember 248 CMR 5.07(5): extra lightning bonding that is electrical work needs proof of an electrical permit before the gas inspector approves — the plumber does not “just land the jumper” as a gas-fitting extra.

Worked isometric 3 — underground notes, regulator, drips

Drawing (described). An LP tank at the right property line. First-stage regulator on the tank hood. Buried PE with tracer brought up at the riser, anodeless riser, second-stage regulator on the exterior wall, then steel into the building. A dashed line under the driveway is labeled “PE, warning tape, 18 in.” A second dashed line is sketched under the slab with a note “vented conduit, LP.” Interior: steel main, a tee with a 6-inch capped nipple at the lowest point of a long basement run (drip), then a pounds-to-inches regulator drawn after a 40-foot interior run to a rooftop unit, with a CSST relief-vent line heading for the roof jack.

Call the fouls. Undiluted LP under the building in the 248 CMR 5.07(1) vented conduit is prohibited — relocate around the footprint. The second-stage regulator belongs outside in this story; that is also the configuration that avoids a PE solely for the short elevated run between stages. Interior piping after the second stage is low pressure unless 5.05(4) says otherwise. The drip at the low point is reasonable; you still need sediment traps at the furnace/boiler/water heater. The CSST relief vent through the roof is the 5.09 trap: transition to steel or wrought iron at least one foot inside — CSST does not become a roof vent. Driveway PE wants the tracer and the burial depth the material and notes require; galvanized is still not the underground coating (248 CMR 5.05(7) plus NFPA 54 7.1.3).

Practical pacing. Seven piping items share 160 minutes with 33 other Part II items. Do not spend eight minutes inventing a pipe size the excerpt does not support. Write developed length, write CFH, enter the column, then spend your remaining seconds on the illegal CSST and the LP under-slab notes — those are fast points when the arithmetic is already done.