Posted by Chris (TX) on July 02, 2002 at 20:31:32:
If you have spoken to septic people you should have your answer. There may not be a cheap way out. It depends on what’s wrong. I have a little experience with septics, but am certainly no expert. At any rate, I’ll tell you what I’ve seen.
I’ve seen the old style clay pipe collapse after years of aging and deterioration. If your systems have clay pipe, that could be the problem. If so, possibly the fix for that would “only” be digging up the collapsed line (and to prevent future problems you probably should just count on digging it all up) and replacing with the newer, updated materials used today.
Another problem could be tree roots penetrating the lines. I’ve seen a 6 foot long spider-web type mass of very small tree roots inhabiting a septic line… filled the whole thing up so that even water couldn’t get through… even though the largest part of the root was no bigger in diameter than an ink pen cartridge… it just had all these extensions off it, that wound around and around each other and it made a solid mass almost. The plumber hadn’t even seen anything like this before. Anyway, once the root was extracted, the water flowed then, but still the pipe had to be dug up to find the break or crack where the root got in, and the offending tree(s) were cut down (I hated that - but the owner of the property didn’t want to ever have the problem again). Larger roots do have a tendency to break pipes as they grow and push on them, so this could be your problem.
Remember, any problem I’ve mentioned could be in the line going to the septic tank(s) or it could be in the lateral field.
I’m sure you’ve had the tanks opened and examined to make sure nothing is clogging the openings…right? And you’ve had them pumped out… right? I’m assuming so, and that they keep backing up in spite of this. I’m also assuming nothing has changed in the area to create excess surface water on your property…and I’m assuming your soil perks.
One thing that can help in park situations, is to put the homes on their own separate water meters and charge the renters/owners of the home according to their own water usage. They say when you do this, the overall water bill for the park usually drops in half. This will decrease the load on the septics immensely.
um… good luck 
Chris