"Me too." wrote in message .net...
"I poured a gallon of vegetable oil down the drain."

Damn, you're braver than me...

If pouring a gallon of vegetable oil down the drain worked, good, no
harm done. That is a new one to me (23 years experience in septic
systems) but it makes sense. I imagine the oil forms a thin layer on
the surface of the tank and helps keep the gases from getting into the
airspace and venting out through the "stack" (vent pipe) on the roof.
The vegetable oil will stay floating in the tank and should not harm
the drainfield. If you don't have to do this too often (e.g. more
than once a year), I can't see any problem. In fact, I may recommend
this procedure to others who call me with the same problem.

Here is another remedy for the same problem: It is based on the same
principal; keeping the gases in the tank rather than letting them flow
out into the house plumbing (through the inlet pipe). Modern septic
tanks are designed to do just that. There is an airspace above the
liquid level in the tank, and it is vented through a "tee" in the
inlet, to allow septic tanks gases such as hydrogen sulfide (rotten
egg smell) to pass out of the tank through the open top of the tee and
upward into the household plumbing, and out of the "stack" in the
roof. Then the odours may downdraft into the yard. So here's the
solution: cap off the top of the inlet tee inside the tank. This
keeps the gases in the tank and allows them to dissipate into the
drainfield where they are absorbed into the soil. You don't smell
them. I have recommended this to many people and they report
overnight success. I know this circumvents the venting design of the
septic tank, but it seems to work, and seems to do no harm

If you have any questions, e-mail me at .

Phil J.