Since you are on a seasonal site you should use pvc. One of the benefits is you never have to disconnect it for storage in the off season.
My TT is on a seasonal site, 12" horizontal pvc to a clear 45* connected to another 45* then 8" down to the septic. It's been in place for 5 years and removed once to use the tote for gray water during a week long stay with 5 in the trailer.
Richard & Jill
2014 Flagstaff 832IKBS Classic Super Lite
2018 Silverado 1500 Crew Cab Z71 4WD All Star Edition
Camping since 1989, seasonal since 2000
Car Shredder Op/Tech, Scrap Metal Recycling - retired
I deserve hazard pay when camping with my relatives.