On Feb 18, 8:40*am, MC wrote:
Thanks for the replies.

The house has been occupied continuously.

Could you guys please clarify something for me. If the tank is 1500
gallons, shouldn't the water level in the tank ALWAYS be at the level
of the outlet pipe (assuming that at least 1500 gallons of water has
been flushed down the drains) if there is no leak?

Sounds about right....

input = output + storage

the water is going somewhere, looks you have a "secondary" or maybe an
alternative primary "leech field".

Like another post said, no surface water, no local wells...I wouldn't
worry about it much.
I'd worry more about a water level 6" above the outlet pipe.

That's how septic systems work.....the tank is supposed to retain
solids, the leech field disperses liquids to the soil.


cheers
Bob