Very old septic system, has worked well for years. CLeaned every 2-3 years. Tree fell across drain field feeder line. Since that time, I think, the septic fills quicker requiring emptying. At last emptying, we put a hole into the drain field line discovering it had air pressure and was dry (until we released the pressure).

It seems that the liquids do not get into the drain field for long then it builds pressure.
Any thoughts? It was suggested that the tree fall may have damaged the feed line to the drain field but I cannot understand if this were the case, the result.

Thanks.

It would be rare but any heavy weight on the feeder could compress or break it. Dig down right where the tree hit the ground. If it is caved in the fix is not all that bad but it will be odoriferous.