Maryland Journeyman Plumber / Gas Fitter

Key Concepts

IPC Chapter 1: Scope, Intent, and Applicability

• IPC §101.2 Scope: The IPC covers erection, installation, alteration, repairs, relocation, replacement, additions, use, and maintenance of plumbing systems. It also regulates nonflammable medical gas, inhalation anesthetic, vacuum piping, nonmedical oxygen systems, and sanitary/condensate vacuum collection systems.
• Critical Exception (§101.2): Detached one- and two-family dwellings and townhouses ≤3 stories with separate egress fall under the International Residential Code (IRC), not the IPC. Fuel gas systems fall under the International Fuel Gas Code (IFGC).
• §101.3 Intent: Establish minimum standards for safety, health, property protection, and public welfare.
• §102.1 Conflicts: Specific requirement beats general requirement; when two sections conflict on materials or methods, the most restrictive governs.
• §102.4 Additions/Alterations: Must conform to requirements for new construction but do not require the entire existing system to be brought into full compliance. Work must not make the existing system unsafe, insanitary, or overloaded.…

Key Concepts

Approved Gas Piping Materials

• Metallic pipe: Steel, wrought iron, or iron pipe per ASTM A53 or equivalent. Must be Schedule 40 minimum for most applications.
• Copper tubing: Permitted for gas piping only if the gas has less than 0.3 grains of hydrogen sulfide per 100 standard cubic feet. Types K, L, or ACR tubing (ASTM B88, ASTM B280).
• CSST (Corrugated Stainless Steel Tubing): Must be listed per ANSI/CSA LC 1. Requires bonding/grounding per manufacturer specs and local requirements.
• Polyethylene (PE) plastic pipe: ASTM D2513 — underground use only. Must be yellow and marked "GAS." Cannot be used above grade.
• Polyamide (PA) tubing: ASTM F2945 — underground use only, similar restrictions to PE.

Key Concepts

Fixture Trap Requirements (IPC §1002.1–1002.3)

• Every plumbing fixture must be separately trapped by a liquid-seal trap — no double trapping.
• Vertical distance from fixture outlet to trap weir: max 24 inches.
• Horizontal distance from fixture outlet centerline to trap inlet centerline: max 30 inches.
• Combination fixtures (e.g., double sinks): one trap is permitted if compartments are no more than 6 inches different in depth and waste outlets are no more than 30 inches apart.
• A grease interceptor may serve as the trap for a single fixture or up to a 3-compartment sink if vertical distance from outlet to interceptor inlet ≤ 30 inches and developed waste pipe length ≤ 60 inches.

Maryland Journeyman Plumber / Gas Fitter Exam — 4 Questions (4%)

Key Concepts

Fixture Materials (IPC Section 402) - All fixtures must have smooth, impervious surfaces free from defects and concealed fouling surfaces (§402.1) - Porcelain enamel surfaces must be acid resistant - Sheet copper: minimum 12 oz/sq ft, conforming to ASTM B152 (§402.3) - Sheet lead for pans: minimum 4 lbs/sq ft, coated with asphalt paint or approved coating (§402.4) - Specialty fixtures must use stainless steel, soapstone, chemical stoneware, plastic, or approved linings (§402.2) - Prohibited: water closets with concealed trap seals, unventilated spaces, or walls not thoroughly washed at discharge; trough urinals (§401.2)

Key Concepts

Backflow Prevention Devices (IPC Chapter 6 / Section 608)

• Air gap: Minimum 2× the effective opening diameter; highest level of protection; non-mechanical; required for direct connections to potable supply at fixtures.
• Vacuum breaker (AVB/PVB): Protects against back-siphonage only; not for backpressure situations. PVBs must be installed 6 inches minimum above highest downstream outlet.
• Double Check Valve Assembly (DCVA): Protects against low-hazard backpressure and back-siphonage (e.g., irrigation without chemicals).
• Reduced Pressure Principle Assembly (RPZ/RP): Highest-rated mechanical device; required for high-hazard cross connections (chemicals, sewage, boilers with additives). Contains two check valves + a relief valve that opens when differential pressure is lost.

Key Concepts

Cross-Connection Hazard Classification

• High hazard (contamination): Risk of illness, injury, or death — sewage, chemicals, pesticides, boiler water with additives. Requires maximum protection (RP assembly or air gap).
• Low hazard (pollution): Nuisance or aesthetically objectionable but not health-threatening — lawn irrigation without fertilizer injection, clean water sources. May allow lesser devices (AVB, PVB).

Backflow Preventer Device Types & ASSE Standards

Key Concepts

Drainage Fixture Units (DFU) are the load-measurement currency of the DWV system. Every fixture has an assigned DFU value used to size all downstream piping (IPC Table 709.1).

Common DFU values to memorize: - Water closet (tank or flush valve): 4 DFU - Bathtub/shower: 2 DFU - Lavatory: 1 DFU - Kitchen sink: 2 DFU - Clothes washer: 2 DFU - Floor drain (2"): 2 DFU - Dishwasher: 2 DFU

Slope requirements (IPC Section 704.1): Horizontal drainage pipe must slope toward the point of disposal. Standard slopes: - Pipe < 3": minimum ¼" per foot (2%) - Pipe ≥ 3": minimum ⅛" per foot (1%)

Key Concepts

Gas Piping Materials & Installation (IFGC Chapter 4) - Approved materials: black steel (Schedule 40), CSST, copper (for LP-gas only where not corrosive), and PE (underground only). Galvanized steel is not approved for gas service. - CSST requires bonding to the electrical grounding system per IFGC Section 310.1. A bond clamp must be installed within 6 feet of the point where CSST enters the structure; wire must be #6 AWG copper minimum. - Underground piping must be protected against corrosion; PE pipe must be installed by heat fusion and cannot be used above ground. - Gas piping cannot be installed in or through air ducts, clothes chutes, chimneys, vents, or elevator shafts.

7 questions | 7% of exam

Key Concepts

Fitting Allowances (Thread Engagement / End-to-End vs. Face-to-Face) Pipe is measured center-to-center or end-to-end; fittings consume pipe length. You must subtract the fitting allowance (also called thread engagement or socket depth) from your cut length. Values differ by pipe type and size — always pull from the correct data table.

Offset Geometry A pipe offset forms a right triangle. The three sides are: - Offset (rise) — perpendicular distance between parallel pipes - Run — horizontal distance traveled - Diagonal (travel) — actual pipe length through the offset

Constants (multipliers) convert the known offset dimension into the unknown: