I have a water closet that has a 4'' pipe the run is 78 ft long before it gets to the septic system it does not work properly. Is it the pitch , size of pipe, the length. it keeps backing up. It's been this way since I been here.
Can someone help me with why it does this and how to fix it.
Thanks . But don't flush

That is a long way. Pipe should be dropped about 16" at this length. What do you have? It could be a sag in the pipe. Have you ever had it augered to the end? Had a camera run through?

Please explain what the toilet does and your concerns. Does it back up? Does it feel to the top swirl around and slowly drain away? The more details you furnish us the better we can help you. Back to you, Tom