"JohnW" wrote in message
...

Our house is approximately 3 years old and we bought it last August 2004.
It has a septic system with drain fields, and a large candycane shaped
vent
. . .
The weather has been rather dry lately, and I have noticed that the grass
over the septic system and drain fields is a bit greener than the other
parts of the yard. I have heard this can be a sign of a problem (but not
necessarily so) and I looked around the neighborhood and saw many similar
situations--perhaps this is the norm.

It is normal for grass over the tile bed to be
greener than elsewhere, because better irrigated.

Still a bit concerned, however, I
walked our yard yesterday (checking to see if the greener areas were
spongy
or had an odor) and was unpleasantly surprised by a strong sewage odor
coming from the yard vent.

What is this "yard vent" ? Septic tanks hereabouts are
not vented. House piping is vented through the roof
(stack vent) and certain atmospheric conditions (usually
still air in winter) can bring stack vent smell to ground level.
But the OP says smell is local to the "yard vent."

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)