I've installed a couple of presby systems. They don't have a pipe off the end of the field. The presby pipes tie together at the capped output end and you have the "candy cane" pipe tied to those that comes up vertically to allow gases to escape so fluid can enter the end closest to the tank. The whole field is bermed and covered with septic sand then covered with top soil and seeded. Never saw a design that had a pipe for overflow, it would compromise the whole purpose of the septic field if it allowed raw sewage to flow past the septic sand.