ckckc2000 said:

that's it-we found that out when we had a blockage no one could roto-rooter out(snake)
the septic is still intact,although the drainage-like the neighbors has failed
and can you believe when they connected the holding tank to the septic they put a 90 degree bend in the drainage pipe-we had the blockage discovered there and they placed an access pipe for when it happens again
Here, any bend before the septic tank requires a cleanout or access pipe...since before the tank you have solids...after the tank, in theory, there should only be liquids and so bends are allowed without a cleanout.
Now, the part about your neighbor is very disgusting

have you ever seen a smokestack on a slightly windy day...and the cloud of smoke starts out small at the smokestack and then gets wider and wider the farther away from the smokestack it gets....air is a fluid and so something similar to this is what is happening under the ground...when your neighbor's junk gets absorbed into the ground...it is sort of like a starting contanimination point and it might be flowing into the groundwater table (if it is close to it) and then it spreads out and seeps into the environment. Then, when you have a bunch of wells pumping water out, that suction is pulling the junk toward the wells and widening how far it travels...just my theory based upon no knowledge, no data and no testing
But, in any case, I wouldn't drink from the well unless you tested your water. We have a filter on our water, but I think overall it is somewhat clean, it comes from the County system
But, there were studies done at one of our beaches...where many condo have really large cesspools...so the waste goes directly into the ground and they found that some of the male fish were becoming femine...too much estrogen in the water

so, I don't take my kids swimming there anymore

Almost a year ago, the EPA changed its rules so those large capacity cesspools have to be removed and septics installed.