Cummins12V98 wrote:
I have literally 125' of 3" pipe from my threaded opening to septic tank and I dump 100 gallons or more at a time FULL BORE at my RV pad with several years of Summer use with ZERO issues.
^^Exactly
A properly functioning septic tank is always full of water up to the bottom of the drain field piping. The drain field consists of no less than 3" pipe, and if it's a traditional system, probably multiple runs of 3" pipe between 100 and 200 lineal feet. 100 feet of 3" pipe will hold about 30 gallons. If the drain field is percolating correctly, you will have no issue at all.