I don't have too much experience with septic systems.

If the house has a septic system, it will also need septic fields, so it's more likely that what you are looking at is something else

I saw what is pobably a leach field below the hill.

Tanks aren't that big and could be a few feet beneath cover. Actual tank cover is below cover you see. Doubt tank is beneath house as a very old tank could collapse. Drain fields could be any where. I've got neighbors that pump uphill to their fields.

Pump chambers are also not uncommon with city sewers as well if the house is located lower than the sewer main.

Wine cellar? Tornado shelter? Thermal heat pump exchange? Could be anything. I doubt it would be a septic tank up the hill with a leach field below the hill. They're almost always nearly level.

Red

Very unlikely. If you have more dealings with it, you might check with the local Health Dept.

And the local sewage haulers could well be able to describe its system.

If it didn't have a basement, and if there are water issues, there may be a French Drain with a pump access in a chamber.

Do you know what a septic tank cover looks like?

My mother was critized for having the septic tank under the patio, because if it had to be dug up, it would ruin the tinted cement patio.

Of course the previous owner had done this, and the tank never caused trouble while we were there. There was a 3 or 4' diameter circle above the tank opening, with dirt and flowers. I was back there 40 years later, but it was covered with snow and I couldn't tell if the original patio was in one piece or not.

I think the tank is under the tank cover, if that's what it is.

No. Tanks are not allowed under the house foundation.

However I have seen it done on older construction. Much older.

Could it be an old water well? I have a property that came with a concrete cylinder about 3 feet across and about 8 inches up out of the ground with a round concrete cap on top. When I opened it up, it was an old shallow water well and there was a well pump in a crawl space under the house that ran to the well.

Or, if it is a septic system -- Like you, I don't have any real experience with septic systems, but I recently found this website that provides a ton of information about how they are constructed, how they work, etc.:

Molly Brown wrote: