7.3 Joints, Connections & Prohibited Practices

7.3 Joints, Connections & Prohibited Practices

Quick Answer: Join Massachusetts plumbing to 248 CMR 10.07 (12/8/2023), not to an IPC joint table. Potable copper is cleaned, reamed to full bore, and soldered or brazed lead-free; press-connect and other mechanical methods follow the manufacturer and Board-accepted methods. Cast-iron hub-and-spigot is oakum or hemp plus molten lead not less than 1 inch deep, one continuous pour, caulked tight, or a resilient gasket. Hubless (no-hub) uses an elastomeric sleeve and stainless clamp; underground clamps must be listed for underground. Plastic DWV is solvent-welded with purple primer where primer is required, unless a UV-detectable clear primer is used and you bring a UV light to inspection. Slip joints belong only on the fixture inlet side of a trap. 248 CMR 10.05(4) bans drainage tees, saddles, tapping of drain or vent pipe, and Sisson joints. It does not use the IPC words “double hub.”

The Candidate Information Bulletin gives Joints and Connections two items. That is not a reason to skim 10.07. A Worcester remodel that solvent-welds PVC to ABS, saddles a 3-inch stack for a new basement sink, or puts a slip joint on the outlet of a trap is already a failed inspection. This section is how Massachusetts wants the joint made, and which fittings 10.05 will not accept.

Copper water, cast iron, plastic, and the other listed methods

Potable copper (10.07(1)). Soldered joints use fittings. Surfaces are thoroughly cleaned, reamed, and returned to full bore. Flux, then lead-free solder, with brass or wrought-copper water fittings. Solder filler metals for potable water shall be lead-free. Flared joints on soft copper use a flaring tool. Threaded copper transitions use brass or wrought-copper adapters; burrs off, full-bore ream, chips out; pipe-joint compound and tape on male threads only; potable threaded joints use lead-free polytetrafluoroethylene sealant. Brazing filler metal and flux for domestic water shall be lead-free. Mechanical methods listed in 10.07(1)(a)5 include press-connect, push-fit to the proper standard, compression, grooved, flanged, tee-forming, ductile iron, and other Board-approved joining methods. Manufacturer instructions govern the press jaw, the insertion depth, and whether a sealing element is for water or for something else. A gas-rated press fitting is not a 10.07 water joint just because it is yellow.

Cast-iron soil pipe (10.07(2)). Caulked hub-and-spigot joints are firmly packed with oakum or hemp, filled with molten lead not less than 1 inch deep, lead run in one continuous pour, and caulked tight. Cornell’s HTML of the “below the rim” leftover dimension is garbled; do not invent a recess figure from an IPC table. What 10.07 clearly requires on the exam is the 1-inch minimum lead depth, the single pour, and a caulked-tight joint. Resilient gaskets are a separate listed method. Hubless joints use an elastomeric sealing sleeve, stainless-steel clamp, clamping screw, and housing. Hubless stainless clamps for underground installation shall be listed for that underground use by the clamp manufacturer. A standard above-grade no-hub band in a buried trench is the wrong product.

Aluminum DWV (10.07(3)) to hubless cast iron uses an end-capped adapter plus the elastomeric sleeve and stainless clamp.

ABS, PVC, and CPVC (10.07(4)(a)) follow manufacturer instructions and may be joined by:

1. Solvent weld per primer and solvent instructions. Where primers are required, they shall be purple. Exception: clear primer is allowed if it is detectable by ultraviolet light, and the licensee makes a UV light detection device available at inspection.
2. Mechanical joints.
3. Threaded joints (with proper male or female adapters on ABS or PVC DWV — 10.07(7)).
4. Shielded stainless-steel clamps.

PEX joints are flared, mechanical, push-fit, or compression, always with pipe and fittings the product manufacturer lists for that system. Polypropylene uses heat fusion (socket, butt, or electrofusion), mechanical/compression, or threaded, again with manufacturer-matched parts. Stainless steel mechanical joints include compression, grooved, flanged, threaded, and press-connect, plus welded joints. Do not mix Brand A PEX tube with Brand B crimp rings because a catalog photo looked similar.

Slip joints, threads, transitions, closet flanges

Slip and ground joints (10.07(6)) are a trap-chapter crossover. Every slip joint uses proper packing or gasket material. Slip joints may only be used on the inlet fixture side of a trap (Example 1). Ground-joint connections that allow adjustment and then make up rigid are allowed within the trap seal (Example 2). Strainers, PO plugs, tailpieces, waste arms, bathtub wastes and overflows, and similar fixture-to-trap parts in ABS, PVC, copper alloy, or other non-corrosive metal shall be at least 17 gauge. A thin tubular slip joint on the outlet of a trap, heading toward the wall, is not 10.07(6)(a).

Threaded joints (10.07(7)) conform to American National Taper Pipe Thread. ABS or PVC DWV uses the proper threaded adapters. Only thread tape, lubricant seal, or other Product-accepted material recommended by the manufacturer.

Transitions (10.07(8)) — unlike materials need listed adapters, not hope:

Closet flanges and floor-outlet fixtures (10.07(11)). Connections from drainage pipe to toilets, floor-outlet service sinks, pedestal urinals, earthenware trap standards, or similar floor-outlet fixtures use brass, wrought copper, hard lead, iron, or plastic flanges caulked, soldered, or solvent-welded to the drainage connection. A gasket, washer, or setting compound is required between fixture and flange. Nuts and bolts are brass, stainless, or other corrosion-resistant metal. The flange is secured to the finished floor with corrosion-resistant screws or bolts. A loose flange sitting on a spongy subfloor is not “secured to finished floor.”

Waterproofing (10.07(12)). Roof-drain and vent penetrations get lead, copper, aluminum, or other flashing. Caps on extended roof flanges fit tight to the inside circumference of the vent and shall not decrease the opening by more than the thickness of the cap material. Exterior wall openings are made watertight.

10.05: how the pipe turns, and what you may not use

Joints are 10.07. Fittings that change direction and fittings that are banned are 248 CMR 10.05(3) and (4). 10.15(8)(a) even sends drainage installations back to 10.05 for pitch, fittings, prohibited fittings, heel or side-inlet bends, and obstructions to flow.

Allowable drainage fittings (10.05(3)(a)). Changes in direction of drainage piping use wyes, long-sweep quarter bends, fifth, sixth, eighth, or sixteenth bends, or their equivalent. Quarter bends (or equivalent) may be used in soil and waste lines when the change is from horizontal to vertical. Tees and crosses for vent fittings may be used for vent piping only. Short-sweep fittings may be used on a branch waste that serves only one outlet when cleanouts comply with 10.08.

Prohibited fittings (10.05(4)(a)) — teach the five bullets as Massachusetts wrote them:

1. No fitting that incorporates a straight T branch as a drainage fitting.
2. No fitting or connection with an enlargement chamber, a recess with a ledge or shoulder, or a reduction in pipe area.
3. No running threads, bands, or saddles in a drainage system. That is the saddle-tap ban.
4. No drainage pipe or vent piping shall be drilled, tapped, burned, or welded.
5. Fittings commonly called Sisson joints are prohibited.

248 CMR 10.05(4) does not say “double hub.” IPC and some UPC commentaries use that phrase for a hub-on-both-ends fitting used as drainage. Do not mark an answer “double hub is listed in 10.05” unless the stem quotes a different document. What 10.05 actually bans is the ledge, shoulder, enlargement chamber, and reduction in area, plus the straight-T, saddle, and tap rules. A hub-to-hub fitting that creates a shoulder in the flow stream fails item 2 even without the IPC nickname.

Obstruction to flow (10.05(4)(b)). No fitting, connection, device, or method that obstructs or retards flow more than normal friction, unless 248 CMR 10.00 specifically allows it. Exception that the exam will offer as a trick: enlarging a 3-inch closet bend or stub to 4 inches is not considered an obstruction provided the horizontal flow line or insert is continuous without forming a ledge (10.05 Example 1). That is the legal closet increaser. A reducer that dumps 4-inch soil into 3-inch with a step is the opposite.

Heel or side-inlet bends (10.05(4)(c), Example 2). A heel or side-inlet quarter bend shall not be used as a dry vent when the inlet is placed in a horizontal position, or any similar arrangement producing a similar effect, except when the entire fitting is part of a dry-vent arrangement. A side-inlet 90 laid on its back so the inlet is a “vent” in the run of a horizontal soil line is the picture Example 2 is there to stop.

Scenario. A Worcester basement adds a lavatory to an existing 3-inch PVC stack. Drilling and saddling the stack is 10.05(4)(a)3 and 4 in one motion. The legal path is a proper sanitary-pattern fitting in a drainage change of direction, solvent-welded with purple primer (or UV-clear primer plus the light at inspection), a 1½-inch trap from 10.08 Table 1, and a cleanout layout that still meets 10.08 after you cut the stack. If the stack is hubless cast iron, the new fitting uses listed hubless clamps; underground portions use underground-listed clamps.

Do not pick solder alloys, primer color, cleanout spacing, or drainage tees from IPC joining or fittings tables. Massachusetts joints are 248 CMR 10.07. Massachusetts fitting bans and the 3-to-4-inch closet enlargement are 248 CMR 10.05.

Official resources

• 248 CMR 10.07 Joints and Connections (Cornell LII) — copper, cast iron, plastic primer, slip joints, closet flanges
• 248 CMR 10.05 General Regulations (Cornell LII) — allowable fittings, prohibited fittings, closet enlargement, side-inlet bends
• 248 CMR 10.05 (UpCodes prohibited-fittings excerpt) — 10.05(4) list and Examples 1 and 2
• 248 CMR 10.00 (Mass.gov) — 12/8/2023 official posting