I learn something almost every day on this forum. Can you post something that I can use to show to contractors to prove this?
Looks like PA has adopted the plumbing sections of the IRC. So then the reference for joints between different materials would would be IRC P3003.13 or IPC 705.16, as applicable. Or for the UPC the reference is UPC 705.10
UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction
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UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction
up.codes
UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction
up.codes
Those sections reference ASTM C1173, C1460, or C1461. C1173 is titled "Standard Specification for Flexible Transition Couplings for Underground Piping Systems," while C1460 is titled "Standard Specification for Shielded Transition Couplings for Use with Dissimilar DWV Pipe and Fittings Above Ground." C1461 covers both use cases but to my understanding products listed under it are relatively uncommon.
Then if you look at the listings on the ~4" long unshielded couplings (or even their shielded versions), you find they are only listed to C1173. The ~2" long shielded couplings are listed to C1460. E.g.
www.fernco.com
www.fernco.com
Now for the case of joining the same material to itself (e.g. you have to cut out some ABS or PVC to rework a section that is between two fixed ends, so you use (2) rubber couplings without a change of material), the reference would be earlier in the same section in each case. Generally there's language like "installed in accordance to manufacturer's instructions." I haven't reread all those sections, but I seem to recall one of them has an allowance to use No-Hub couplings for plastic to plastic joints. [Unless that was a state-specific amendment I'm remembering.]
And to clarify, the coupling on the right in the picture is a No-Hub coupling listed for connecting cast iron to cast iron (presumably has its own ASTM standard that I didn't look up), not an ASTM C1460 coupling. You can tell because of the corrugated shield, rather than a flat shield.
Cheers, Wayne