10.1 Gas Piping Installation, Testing & Purging

10.1 Gas Piping Installation, Testing & Purging

Proper physical support, underground burial protection, pressure testing, and safe purging protocols are vital components of fuel gas system installation under the International Fuel Gas Code (IFGC Section 406) and Maryland Plumbing Regulations. Journeyman candidates must know exact hanger spacing intervals, underground burial depths, pressure testing values, gauge limitations, and safety procedures for purging gas lines prior to commissioning.

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1. Gas Piping Support & Hanger Spacing

Gas piping must be supported with pipe hooks, metal straps, bands, or hangers of suitable strength and material to prevent sagging, vibration, and strain on joints.

IFGC Pipe Support Spacing Requirements

Code Rule: Gas piping must not support other piping or structural loads. Support hangers must be attached directly to structural building members (joists, studs, concrete) and insulated from galvanic contact when supporting dissimilar metals.

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2. Underground Gas Piping Installation Standards

Underground fuel gas piping requires specialized burial depth, corrosion protection, and location tracing to prevent accidental strike damage during future excavation:

Burial Depth Rules

• Standard Minimum Cover: Underground piping must be installed with a minimum cover of 12 inches below finished grade.
• The only exception is shallower, not deeper: IFGC 404.12.1 allows individual lines to outdoor lights, grills and similar appliances at 8 inches below finished grade where approved and not susceptible to physical damage. There is no 18-inch provision anywhere in IFGC Chapter 4 - the 18-inch increase for likely external damage is a Uniform Plumbing Code rule (UPC 1210.1.6) and a common distractor.
• Trench Bedding: IFGC 404.13 requires only that the trench be graded so the pipe has a firm, substantially continuous bearing on the trench bottom; clean sand or screened backfill is good practice rather than a code-stated material.

Wall Penetrations & Sleeves

• IFGC 404.6 Underground Penetrations Prohibited is absolute: gas piping shall not penetrate building foundation walls at any point below grade. The piping must enter and exit the building above grade, and the annular space between pipe and wall must be sealed.
• The annular space between the pipe and sleeve must be sealed with a flexible, non-hardening, water-tight sealant to prevent gas or water infiltration into the basement.

PE Plastic Underground Rules & Tracer Wire

• Polyethylene (PE) pipe must be installed underground only.
• Tracer Wire Requirement: An insulated, continuous copper tracer wire (minimum #18 AWG yellow insulated wire) must be buried alongside non-metallic plastic piping. One end of the tracer wire must terminate above grade at an accessible riser location to allow electronic pipe locators to trace the buried line.

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3. Fuel Gas Pressure Testing Protocols (IFGC Section 406)

Prior to appliance connection or concealment within walls/floors, all new, extended, or altered fuel gas piping systems must undergo a rough-in hydrostatic or pneumatic pressure test.

Required Test Pressure & Duration

Test Gauge Requirements

• IFGC 406.4: mechanical gauges used to measure test pressure must have a range such that the highest end of the scale is not greater than 5 times the test pressure. The rule governs the gauge's full-scale range, not its dial increment.
• For a standard 3 psi pressure test, the test gauge must have a full-scale range no greater than 0 to 15 psi, with increments of $0.1\text{ psi}$ or $0.2\text{ psi}$.
• Using a 0-100 psi or 0-200 psi gauge for a 3 psi test is a direct code violation because small pressure drops cannot be visually detected on large scale dials.

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4. Gas Line Purging Procedures & Safety (IFGC Section 406.7)

After pressure testing passes and prior to initial light-off, gas piping systems must be purged of air or test medium to prevent combustible fuel-air mixtures inside the piping.

Purging Execution Standards

1. Piping Thresholds: IFGC 406.7.1 sends a system outdoors when either the design operating pressure exceeds 2 psig, or the piping contains a section meeting the paired size-and-length criteria of Table 406.7.1.1: 2-1/2 to under 3 in. and over 50 ft; 3 to under 4 in. and over 30 ft; 4 to under 6 in. and over 15 ft; 6 to under 8 in. and over 10 ft; 8 in. and larger at any length. Size alone never triggers it - a 2-1/2-inch, 30-foot run falls outside the table.
2. Outdoor Discharge Location: IFGC 406.7.1.3 sets three different distances: not less than 10 feet from sources of ignition, not less than 10 feet from building openings, and not less than 25 feet from mechanical air intake openings. The discharge point is valved, continuously attended and monitored with a combustible gas indicator, and anyone not involved is kept 10 feet clear.
3. Safety Precautions:
   • Eliminate all open flames, electrical switches, or hot work in the immediate area.
   • Monitor the discharge with a Combustible Gas Indicator (CGI). IFGC 406.7.1.3, item 4 requires purging that introduces fuel gas to be stopped when 90 percent fuel gas by volume is detected in the pipe - not at 100 percent.

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5. Exam Traps & Inspection Guidelines

1. Prohibited Test Media Trap: Any test question suggesting Oxygen ($O_2$) as a pressure test gas is an immediate explosive hazard and a false choice.
2. Burial Depth Confusions: IFGC gives 12 inches standard and 8 inches for individual outdoor appliances. The 18-inch "under driveways" figure is a UPC rule and does not appear in the IFGC.
3. Tracer Wire Specification: Minimum #18 AWG insulated copper tracer wire for PE plastic pipe.
4. Gauge Range Rule: Remember that gauge range cannot exceed 5x test pressure (max 15 psi gauge for a 3 psi test).