Plumbing & fuel gas code

Administration

• The Board of State Examiners of Plumbers and Gas Fitters administers 248 CMR
• Plumbing permits are issued only to properly licensed individuals — never to apprentices. When the work is for a corporation, LLC or partnership, only its Master Plumber officer/manager/partner is issued the permit (248 CMR 3.05(1)(b)7)
• A permit becomes invalid if work is not started within 90 days of the permit date, unless the holder proves the delay was beyond their control (248 CMR 3.05(1)(e))
• Rough-in plumbing must be inspected before concealment of piping
• The Inspector may require a rough and a final inspection; notice that work is ready for final inspection must be given within five days after the plumbing work is complete (248 CMR 3.05(3)(b), 10.04(2)(b))

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 330 education hours (the first three tiers) 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 licensed apprentices under direct supervision)

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

• Journeyman: Part I — 80 questions / 160 minutes; Part II — 40 questions / 160 minutes
• Master: Part I — 80 questions / 160 minutes; Part II — 40 questions / 160 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: A piping arrangement in which a drain discharges indirectly into a fixture, receptacle or interceptor at a point below the flood-level rim of the receptacle
• 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 in the drainage system, conveying waste to the building sewer; in MA it extends 10 feet in developed length from the inside face of the foundation wall
• 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): One cubic foot of water (7.5 gallons) drained in a 1-1/4 inch pipe over one minute; fixture values are listed in 248 CMR 10.15 Table 1
• Flood-Level Rim: The edge of the receptacle from which water overflows
• Potable Water: Water that does not contain impurities in amounts sufficient to cause disease or harmful physiological effects; quality must conform to 310 CMR 22.00
• Stack Vent: The portion of a soil or waste stack that is 6 inches above the flood-level rim of the highest fixture connected to the stack
• 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

• Second-hand or previously installed fixtures and materials may be reinstalled if they comply with 248 CMR 10.00, and must be thoroughly cleansed and disinfected before installation
• 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

• Which copper types (K, L, M, DWV) are allowed for water distribution above and below ground is set by 248 CMR 10.06 Table 2 — check the table for each use

Drainage Materials

• Allowed materials: see 248 CMR 10.06 Table 1. PVC and ABS Schedule 40 DWV is limited to residential buildings (and residential areas of assisted living) not exceeding ten stories, and is prohibited in commercial kitchens, laundry rooms and public toilet facilities
• Which DWV materials are allowed above and below ground is set by 248 CMR 10.06 Table 1 — check the table for each material
• PVC DWV is Schedule 40 pipe and fittings (248 CMR 10.06(2)(g)); product standards must be accepted under 248 CMR 3.04

PEX

• PEX and CPVC may be used for hot and cold water piping only in residential dwellings, hotels, motels, inns, condominiums and similar buildings not exceeding six stories (plus the limited exceptions in 248 CMR 10.06(2)(f))
• No PEX or CPVC within 24 inches of the final connection to a water heater (248 CMR 10.06)

• Only lead-free solder and flux on potable water joints (248 CMR 10.07(1)(a)1.)
• Solvent-weld per the primer and cement manufacturer's instructions; where primer is required it must be purple (clear primer only if UV-detectable, with a UV light available at inspection)
• Copper tubing to threaded pipe transitions use brass or wrought copper adapter fittings; dielectric unions and fittings are allowed, and unions between dissimilar metals must be dielectric type
• No-hub cast iron joins with an elastomeric sealing sleeve and stainless-steel clamp; hub-and-spigot uses resilient gaskets or oakum with molten lead not less than 1 inch deep
• Threaded joints use tapered NPT threads with approved sealant
• Slip joints may only be used on the inlet (fixture) side of a trap and must use proper packing or gasket material

Trap Rules

• Water seal: not less than 2 inches, not more than 4 inches
• Prohibited traps: full S-traps, bell traps, crown-vented traps, traps with moving parts, and separate traps that depend on interior partitions
• 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: 50 feet for drains 4" and smaller; 100 feet for larger drains
• 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

• Public/employee toilets, urinals and lavatories: minimum 15 inches centerline to a side wall, 30 inches center-to-center to another fixture, and 21 inches clear in front
• 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 120°F

Minimum Fixtures (Restaurants)

• Horizontal copper tube 1-1/4" and smaller: 6-foot intervals; 1-1/2" and larger: 10-foot intervals
• Horizontal cast iron soil pipe: every 5 feet (every 10 feet when 10-foot lengths are used); vertical: at the base and each story
• Horizontal plastic pipe: 1-1/2" and smaller every 3 feet; 2" and larger every 4 feet. CPVC: 1" and smaller every 3 feet, larger every 4 feet. PEX: per manufacturer
• Vertical piping: cast iron at the base and each story; copper, plastic and stainless at each story but not more than 10 feet; threaded pipe every other 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: the indirect waste outlet terminates below the flood-level rim of the receptor
• 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
• A domestic dishwasher may be separately trapped, connected to the disposer inlet, or connected with a wye between the sink outlet and the trap inlet (248 CMR 10.08(2)(a)1.a.iv.)

• 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

• Size the water service and building main from fixture factor values × demand factor using 248 CMR 10.14 Tables 1–3; protect water piping from freezing (248 CMR 10.05(7)(b))
• 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
• Water or drainage piping in exterior walls or unconditioned spaces must be protected from freezing (248 CMR 10.05(7)(b))

Hot Water

• Residential hot water: minimum 120°F, maximum 130°F; public & employee lavatories max 120°F
• T&P relief valve: temperature relief prevents water above 212°F; pressure setting not more than the tank's stamped maximum working pressure; installed within 12 in. of the top of a vertical tank; discharge full-size, non-ferrous, no shut-off, to a fixture or to within 12 inches of the floor
• All tank-type water heaters and storage tanks require a vacuum relief valve in the cold supply above the top of the tank, with no shutoff between it and the tank
• 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 with chemicals, chemical feed); tested every 6 months (310 CMR 22.22(13)(d)); installed horizontally 3 to 4 feet from the floor to the bottom of the device and at least 12 inches from any wall; pit installation only where specifically approved by MassDEP or the water system
• DCVA: low-hazard (pollutant) connections only
• AVB: min 6 inches above highest downstream outlet
• Sillcocks, hose connections and wall hydrants (including faucets with hose threads) require a backflow preventer or vacuum breaker (at minimum an AVB); irrigation systems need an approved device (lawn sprinkler critical level at least 12 in. above the highest head)

Slope

DFU Values (Common Fixtures)

Sizing

• Underground drainage piping: minimum 2 inches; sanitary piping through the foundation wall: minimum 4 inches (248 CMR 10.15(6))
• 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 valves may be installed only on drain piping serving fixtures subject to backflow from the public sewer; drains not subject to backflow shall not drain through a backwater valve
• 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"; a 3" water closet drain therefore needs a 1-1/2" vent (2" when underground or below a basement floor)
• Vent stack minimum: 3 inches; required once a building has 3 or more branch intervals (248 CMR 10.16(2)(a))
• 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)
• Vent size is set by developed length and total fixture units using 248 CMR 10.16 Table 2 (no flat 40-ft upsize rule)
• AAVs (air admittance valves) are generally prohibited in Massachusetts without specific Board approval

Roof Terminals

• Extend 18 to 24 inches above the roof penetration; 8 ft if the roof is used as a deck, garden or parking (248 CMR 10.16(3)(a)1)
• Minimum 3 inches through the roof (frost closure) — any increase made ≥1 ft below the roof
• Within 10 ft horizontally of a building opening (window/door): terminate at least 2 ft above the top of the opening. Forced-air intakes: at least 25 ft horizontally, or as close as 10 ft if at least 2 ft above the intake

Trap Arm Maximum Distances (trap to vent)

Vent Types

• Common vent: two same-level fixtures sharing one vent
• Wet vent: in a bathroom with a 2" horizontal waste, a 2" extension of the drain to the lavatory may wet-vent the bathroom fixtures; kitchen sinks, disposals, dishwashers, washing machines and culinary fixtures may not serve as wet vents
• Circuit vent: up to 8 fixtures in battery on a horizontal branch
• Bow vent: permitted when a sink or lavatory vent cannot rise 6 in. above the flood-level rim before turning horizontal (e.g. island sinks); sized per 248 CMR 10.16 Table 2. (In MA a loop vent is a battery vent for 2–8 floor-outlet fixtures.)
• Vent headers connect at the top of the stacks; the roof extension is 5" when more than two 4" stacks connect and 6" when more than four 4" stacks connect

• Storm piping is sized by projected (roof/area) square footage using 248 CMR 10.17 Tables 1–2, which are based on a 4 in/hr rainfall rate; continuous clear-water flow counts 24 sq ft per gpm — 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
• Medical gas installer certification, brazing under nitrogen purge, system verification and color coding come from NFPA 99 and the ASSE 6000-series standards, not from 248 CMR 10.18

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 — Massachusetts Fuel Gas Code (purpose, adoption, definitions); 248 CMR 4.00 through 8.00 together make up the Massachusetts Fuel Gas Code
• 248 CMR 5.00 — Massachusetts amendments to NFPA 54 (National Fuel Gas Code)
• 248 CMR 8.00 — current Massachusetts amendments to NFPA 58 (the PSI bulletin lists the older 6.00 reference; see the NFPA 58 section below)
• 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 the listed Massachusetts regulations plus NFPA 54/58 as amended by Massachusetts, so a national NFPA answer can be wrong here. Always follow the MA amendment.

• Private sewage disposal (septic) is governed by Title 5, 310 CMR 15.00 (DEP), not 248 CMR
• Septic tanks watertight; minimum effective liquid capacity 1,500 gallons (200% of design flow for a single-family dwelling)
• 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