It seems from another post that the adopted plumbing code in Fairfield County is the International Plumbing Code. As such - the minimum clean-out for a 6" pipe is 4" - See excerpt below:

708.7 Minimum size. Cleanouts shall be the same nominal size as the pipe they serve up to 4 inches (102 mm). For pipes larger than 4 inches (102 mm) nominal size, the minimum size of the cleanout shall be 4 inches (102 mm).

There are a couple exceptions though for "p" traps, stack clean-outs, or cast-iron clean-outs. Do any of these three items apply?

Greetings

no the items does not apply.Thank you very much for your help.