Indian Health Service installed a new septic system for us a few years back. They could not run an extra "clean out" to my RV site, but the installer did put in a "Y" joint. It was about 25' from the nearest cleanout to where I wanted the RV dump, er, extra cleanout. I dug the ditch, tied 4" Schedule 40 PVC into the "Y," and ran the 25 or so feet of pipe to my RV site. Works great - one of my better ideas. Glued all my connections. If this, or any other piece of pipe ever needs to be removed, I'll just cut it off. A good recip saw works wonders for this job.
GM