I remember when my parents moved into their house the previous owners supplied the house via a well.
The summer we moved in we switched to mains for the water, but kept ‘off grid’ with the sewerage, one of the largest factors was that the water table was so low that summer we spent too much time (money/plastic) getting water and another was the salmonella in it…
As all of the grey water etc now feeds into the menage/paddock, we have patches of suspiciously luscious grass and if you look out of a top window in the house you can trace where the pipes are laid. The moles also like it as it is nice and toasty and warm when someone has a shower so there are many many mounds.