Administration

• The Board of State Examiners of Plumbers and Gas Fitters administers 248 CMR
• Only a licensed Master Plumber can obtain a plumbing permit
• A plumbing permit is valid for 1 year from date of issuance
• Rough-in plumbing must be inspected before concealment of piping
• A final inspection is required before a new system is placed in service

License Types & Requirements (248 CMR 11.02)

• Apprentice: Licensed by the Board; works under the direct supervision of a Massachusetts licensed journeyman or master plumber
• Journeyman: No less than 6,800 clock hours of practical work experience as a licensed apprentice, plus 550 clock hours of tier education (five 110-hour tiers), then the written exam
• Master: Held a journeyman license at least 1 year, plus 1,700 clock hours of qualifying work and Tier 5 (110 hours), then the master exam. Can pull permits, run a plumbing business, and supervise

How the 6,800 hours are earned (248 CMR 11.02)

• The pathway pairs work with school: for each year an apprentice obtains 165 clock hours of education (1½ tiers), they must accrue 1,700 clock hours of qualifying work experience
• 4 years × 1,700 hours = 6,800 clock hours — that's the "four years" everyone quotes
• A licensed apprentice may complete all 220 hours of Tier 1 and Tier 2 in a single calendar year; an unlicensed individual may complete Tier 1 before licensure
• Vocational-technical credit: graduates of an approved public comprehensive high school career/vo-tech plumbing program may receive up to 300 education hours and 1,700 experience hours of credit
• Legacy standard: apprentices licensed before September 1, 2008 were held to 8,000 clock hours — that's why older sources cite 8,000

Renewal & Continuing Education (248 CMR 11.04)

• Licenses renew every 2 years
• 12 hours of Board-approved Mandatory Continuing Education (MCE) is required for renewal

Requirements above are drawn from 248 CMR 11.00 — Education and Experience Standards and Requirements for Licensure. The Board periodically amends 248 CMR 11.00; always confirm current requirements and the PSI candidate bulletin at mass.gov before applying.

Permits

• Permit required for: new fixtures, water heaters, water piping, gas piping
• Permit NOT required for: replacing washers or flappers, clearing drain stoppages
• Permitted work is performed by licensed plumbers (or registered apprentices under supervision)

The Exams (administered by PSI — closed book, computer-based, two parts)

• Journeyman: Part I — 70 questions / 150 minutes; Part II — 30 questions / 120 minutes
• Master: Part I — 60 questions / 120 minutes; Part II — 30 questions / 120 minutes
• Passing score: 70% on each part
• Questions are drawn from 248 CMR, MGL c. 142, and for gas NFPA 54 / NFPA 58 as amended — plus general trade practice
• Topic areas: general regulations/inspections/permits · gas piping, equipment & appliances · venting · traps & cleanouts · fixtures, equipment & clearances · water heaters · piping, valves & controls · water supply · hangers & supports · drain, waste & vent · separators/interceptors/grease traps · joints & connections
• Master eligibility: 1 year as a licensed Journeyman + 1,700 hours + Tier 5 (110 hrs)
• Licenses renew every 2 years with 12 hours of continuing education
• Confirm current requirements, fees, and the official content outline in the PSI candidate bulletin and at mass.gov before applying

Key Definitions

• Air Gap: The unobstructed vertical distance through free atmosphere between the lowest supply opening and the flood-level rim of the receptacle
• Air Break: An indirect waste connection terminating below the receptor's flood rim but above the trap seal
• Backflow: Flow into the potable distribution from any source other than the intended source — caused by backpressure or backsiphonage
• Branch: Any part of the piping system other than a main, riser, or stack
• Branch Interval: A stack section at least 8 feet high within which the horizontal branches of one story connect
• Building Drain: The lowest piping receiving discharge inside the building, conveying it to the building sewer
• Building Sewer: Horizontal piping from the building drain to the main sewer or point of disposal
• Cross-Connection: Any connection between potable water and water of unknown or questionable safety
• Fixture Unit (DFU): The load-producing value assigned to a fixture for drainage sizing
• Flood-Level Rim: The edge of the receptacle from which water overflows
• Potable Water: Water safe and satisfactory for drinking, cooking, and bathing
• Stack Vent: The dry extension of a soil/waste stack above the highest horizontal branch
• Trap: A fitting providing a liquid seal against sewer gas without materially affecting flow
• Wet Vent: A pipe serving as a vent for one fixture and a drain for another

DWV Testing

• Rough-in water test: fill to a minimum 10-foot head of water (no section tested with less), kept in the system at least 15 minutes before inspection starts — then tight at all points
• Air test alternative: a uniform 5 PSIG (or 10 inches of mercury) held 15 minutes without adding air; gauge calibrated in increments no greater than 1/10 pound
• Testing happens before concealment and before the inspector's rough approval

Water Piping

• The roughed water supply system is tested and proved tight at not less than 125 psi

• Used (secondhand) fixtures and materials may be reinstalled only if approved and restored to good, sanitary working condition
• All work must be performed in a workmanlike manner and conform to 248 CMR
• Piping must be protected from freezing, corrosion, and physical damage

Copper Tube Types

• Type K (green) — heaviest wall; required for underground water service
• Type L (blue) — general purpose water distribution
• Type M (red) — thinnest standard wall; generally above-ground use inside buildings
• DWV (yellow) — drainage/vent only

Drainage Materials

• Approved underground: cast iron, PVC (Schedule 40), ABS
• NOT approved underground: galvanized steel (corrosion)
• PVC DWV conforms to ASTM D1785 (Sch 40) or ASTM D2665

PEX

• Approved for water distribution per its listing
• Keep at least 18 inches of metallic piping between PEX and a water heater connection

• Only lead-free solder (≤0.2% lead) on potable water joints
• PVC solvent joints require an approved primer before cement (ABS is cemented without primer)
• Copper to galvanized steel requires a dielectric fitting (prevents galvanic corrosion)
• No-hub cast iron joins with shielded couplings; hub-and-spigot uses gaskets or lead & oakum, hubs laid facing upstream
• Threaded joints use tapered NPT threads with approved sealant
• Concealed slip joints require an access panel for inspection

Trap Rules

• Water seal: not less than 2 inches, not more than 4 inches
• S-traps are prohibited (self-siphoning); double trapping is prohibited
• One trap per fixture — narrow exceptions such as adjacent compartments of a multi-compartment sink
• Traps subject to evaporation need a trap seal primer or equivalent protection

Cleanouts

• Required at every change of direction greater than 45°
• Required at or near the base of every stack
• Maximum spacing on horizontal drains: 75 feet
• Size: same as the pipe served (up to 4"); 4" cleanout acceptable for larger pipes
• Must remain accessible

• Grease interceptors required for commercial kitchen fixtures discharging grease-laden waste
• Food waste grinders must NOT discharge through a grease interceptor — they connect separately
• Oil/sand separators serve garages and similar occupancies
• Interceptors must be sized per the fixtures served and be accessible for cleaning

Fixture Trap Sizes

Installation Rules

• Water closet centerline: minimum 15 inches to any side wall, partition, or fixture
• Public-use water closets: elongated bowls with open-front seats
• Maximum flush volume for new water closets: 1.6 gallons
• Fixture overflows connect on the inlet (fixture) side of the trap
• Fixture joints at walls/floors sealed watertight
• Shower valves: pressure-balancing or thermostatic, max 112°F
• Hot water is always supplied to the left side of a fitting

Minimum Fixtures (Restaurants)

• Horizontal copper tube (1" and smaller): support at maximum 6-foot intervals
• Cast iron: support at each joint / every 5 feet
• Plastic piping requires closer support spacing than metal (typically 4 feet)
• Vertical piping supported at each story

• Air gap: terminates above the receptor's flood rim (full separation); the gap must be at least twice the effective diameter of the drain served
• Air break: terminates below the rim but above the trap seal
• The indirect waste is never trapped ahead of the air gap or air-break — the receiving fixture provides the trap and vent
• The receptor must be an open, accessible, properly trapped and vented sink, floor drain, or fixture
• Commercial food-handling equipment discharges indirectly (air gap or air break) to a trapped receptor
• Massachusetts requires a listed air gap fitting on dishwasher drains — a high loop alone is not acceptable

• Corrosive chemical / laboratory waste requires approved acid-resistant piping
• Special wastes are neutralized or treated before entering the sanitary drainage system — adjusted to a pH between 6 and 9
• The neutralizing device is automatically supplied with enough neutralizing medium to render its contents non-injurious
• Treated discharge connects to the building sanitary drain/sewer no closer than 10 feet from the neutralization system

Service & Pressure

• Minimum water service size: 3/4 inch; minimum burial depth in MA: 48 inches
• Water service vs. building sewer separation: 10 feet horizontal (or approved shelf installation)
• Maximum static pressure at fixtures: 80 psi (PRV required above that)
• Full-port shutoff at the service entrance; stop valve at each fixture supply; shutoff at each water heater
• Water hammer arrestors where quick-closing valves are installed
• Piping in exterior walls protected on the heated side of insulation

Hot Water

• Residential fixtures: minimum 110°F; public handwashing max 110°F tempered
• T&P relief valve: opens at 210°F / 150 psi; discharge full-size, unthreaded, terminating near the floor
• Bottom-fed water heaters require a vacuum relief valve
• Thermal expansion tank required on closed systems (backflow preventer on service)

Minimum Fixture Supply Sizes

Backflow Prevention

• Backflow occurs by backpressure or backsiphonage
• Air gap: simplest and most reliable — min 1 inch or 2× outlet diameter, whichever is greater
• RPZ: high-hazard connections (boiler makeup, chemical feed); tested annually; min 12 inches above floor, never in a pit
• DCVA: low-hazard (pollutant) connections only
• AVB: min 6 inches above highest downstream outlet
• Hose bibbs require a non-removable vacuum breaker; irrigation systems require an approved assembly

Slope

DFU Values (Common Fixtures)

Sizing

• Minimum building drain receiving a WC: 3 inches
• Minimum building sewer: 4 inches
• Piping at 45° or less from vertical is treated as vertical

Fittings

• Sanitary tee: horizontal-to-vertical only — never horizontal-to-horizontal or vertical-to-horizontal
• Horizontal-to-horizontal: use a wye or combination wye & 1/8 bend (long-pattern fittings)

Protection

• Backwater valve required when fixture flood rims are below the next upstream manhole cover
• Sewage ejector discharge: check valve + full-open shutoff

Purpose & Basics

• Vents equalize pressure and protect trap seals from siphonage and back-pressure
• Vent size: at least half the drain served, never under 1-1/4"; WC vent minimum 2 inches
• Vent stack minimum: 2 inches; required for stacks of 5+ branch intervals
• Relief vent at each 10th branch interval on stacks over 10 intervals
• Vents graded to drain back by gravity; dry vents take off vertically above the drain centerline
• No vent connection within 2 pipe diameters of the trap weir (no crown venting)
• Vents over 40 ft developed length increase one pipe size
• AAVs (air admittance valves) are generally prohibited in Massachusetts without specific Board approval

Roof Terminals

• Extend at least 12 inches above the roof
• Minimum 3 inches through the roof (frost closure) — any increase made ≥1 ft below the roof
• Within 10 ft horizontally of a window/door/air intake: terminate at least 2 ft above the opening

Trap Arm Maximum Distances (trap to vent)

Vent Types

• Common vent: two same-level fixtures sharing one vent
• Wet vent: vent for one fixture, drain for another — sized for the total load
• Circuit vent: up to 8 fixtures in battery on a horizontal branch
• Island (loop) vent: for island sinks where conventional venting is impractical
• Combined vent headers sized for the total DFU served

• Storm piping is sized by roof area and local rainfall rate — never by DFU
• Storm water shall not discharge to the sanitary system (or to a septic system)

• Sterilizers: individual and separate indirect wastes; air gap ≥ 2× the waste tailpiece diameter; p-trap on the discharge side, immediately below the indirect waste connection
• A battery of no more than 3 sterilizer wastes may share one trap, sized to the combined fixture units
• Bedpan steamer: trap with a minimum 3-inch seal between fixture and indirect waste connection
• Recess rooms hiding sterilizer internals need a floor drain placed to drain the entire floor
• Installation by ASSE 6010 certified personnel only
• Type L (or K) copper, cleaned and capped for oxygen service (ASTM B819)
• Joints brazed with BCuP alloy under continuous nitrogen purge — soldering prohibited
• System verification by an independent ASSE 6030 verifier before use
• U.S. color code: oxygen = green

How Massachusetts organizes fuel gas

• 248 CMR 3.00 — General provisions governing the conduct of plumbing and gas work (licensing conduct, business/apprentice licenses, inspector requirements)
• 248 CMR 4.00 — The Massachusetts Fuel Gas Code — the umbrella gas regulation
• 248 CMR 5.00 — Massachusetts amendments to NFPA 54 (National Fuel Gas Code)
• 248 CMR 6.00 — Massachusetts amendments to NFPA 58 (Liquefied Petroleum Gas Code)
• 248 CMR 7.00 — Large gas utilization equipment
• 248 CMR 10.00 — Uniform State Plumbing Code · 248 CMR 11.00 — Education & experience standards

Why it matters: in Massachusetts, gas fitting is licensed together with plumbing — the journeyman exam tests both. Gas questions come from 248 CMR 4.00–7.00 plus NFPA 54/58 as amended by Massachusetts, so a national NFPA answer can be wrong here. Always follow the MA amendment.

General Rules

• Minimum gas pipe size meter → appliance: 1/2 inch
• Max pressure drop (low-pressure system): 0.5 inch WC
• Sediment trap (drip leg) at every appliance inlet
• Shutoff valve at the meter and within 6 feet of each appliance
• Sizing based on BTU demand, run length, pressure drop, and specific gravity
• Appliances in bedrooms/bathrooms must be direct-vent (sealed combustion)
• Confined spaces need two combustion-air openings (top and bottom)

Materials & Installation

• Black iron: threaded or welded; approved gas-rated thread compound only
• CSST must be bonded to the grounding system
• PE plastic: underground outdoors only, with tracer wire and approved riser
• Underground burial: minimum 12 inches of cover
• Through masonry: sleeved; never through ducts, chimneys, or elevator shafts
• Flexible appliance connectors: max 6 feet, never through walls or floors
• Regulator vents terminate outdoors, protected, away from openings

Testing & Safety

• New piping test: 3 psi for 10 minutes, no perceptible drop (air/inert gas only)
• Leak checks with solution or gauge — never a flame
• LP gas is heavier than air and pools in low areas

Venting Appliances (Categories I–IV)

• Category I — negative vent pressure, non-condensing (atmospheric furnaces, most water heaters): vented with B-vent or masonry chimney
• Category III — positive pressure, non-condensing: requires listed, gas-tight special vent
• Category IV — positive pressure, condensing (high-efficiency): vented with listed plastic (PVC/CPVC/PP) per the manufacturer, with a condensate drain
• Vent connectors slope upward at least 1/4 inch per foot toward the vent
• Never connect an appliance to a vent serving a solid-fuel appliance

Combustion Air (NFPA 54 as amended)

• Standard method for a confined space using indoor air: 1 square inch per 1,000 BTU/hr per opening, minimum 100 sq in each, one high and one low
• Using outdoor air through vertical ducts: 1 sq in per 4,000 BTU/hr; horizontal ducts: 1 sq in per 2,000 BTU/hr
• An unconfined space has at least 50 cubic feet per 1,000 BTU/hr of total input

LP Gas (NFPA 58 as amended — 248 CMR 6.00)

• LP is heavier than air (vapor density ~1.5) — it settles; natural gas rises
• Approx. 2,500 BTU per cubic foot (vs ~1,000 for natural gas); ~91,500 BTU per gallon
• Typical appliance manifold pressure: 11 in WC for LP vs 3.5 in WC for natural gas
• Container placement, clearances to openings/ignition sources, and filling limits are set by NFPA 58 as amended
• Never install LP appliances or containers in basements/pits where vapor can accumulate

Massachusetts-Specific Gas Notes

• Gas fitting is licensed with plumbing in MA — the journeyman exam covers both
• MA amendments in 248 CMR 5.00/6.00 override the base NFPA text — answer to the amendment
• 248 CMR 7.00 governs large gas utilization equipment
• Gas permits and inspections follow the same Board/inspector process as plumbing

Gas Pipe Sizing (Common)

• Private sewage disposal (septic) is governed by Title 5, 310 CMR 15.00 (DEP), not 248 CMR
• Septic tanks watertight; residential minimum typically 1,000 gallons
• Leaching design based on percolation tests; Title 5 inspection required for property transfer
• No storm water to the septic system; grease traps before septic for food service