The rule is that the cleanout has to have an opening the same size as the pipe up to 4". Above 4" a 4" opening is all that is "required", but it looks like they installed a 6" cleanout which is better, but no required, but a sweep fitting would be what a plumber would have had to use to get passed by an inspector. To be honest, the job looks like what a handyman would have done, i.e., using a tee, thin pipe for the riser and a slip on cap rather than a screwed in plug., none of them to "plumber" standards. It is useless for snaking towards the house because of the two elbows adjacent to it, and the pipe to the street, from that point, seldom, if ever, gets plugged up.
