On Wed, 23 Jul 2003 18:45:03 -0500 (CDT), (mark
Ransley) wrote (with possible editing):

to TOM J Yess you are right , through the attic, But why at the
tank ? now and not on old systems

FWIW, I think (as Bill said earlier) that new systems are based on
aerobic bacteria which produce less methane and carbon dioxide - or
perhaps none at all. The older ones were vented only at the stack and
use anaerobic digestion. This might be considered more
environmentally friendly, but I have to admit that my old system has
been running properly for 30 years now without pumping. Three years
ago, I added a new (second) system (because we expanded the size of
the house) and had it designed without vents (both types are accepted
in New Hampshire in the US) for the same reason: no stink.

Our only provision is to keep gray water out of them, and that is to
keep out phosphates.

--
Larry