Septic tank, bad idea.
On more than one occasion I watched a tank get pumped during a warrant service.

I spent ten years searching for stolen goods, dope, guns and money.

If you can get to it easily, it can be found.
Loose floorboards , the floor is coming up.
Loose mopboard, its coming off.
Paint lines don’t match, you guess.
Plumbing, you tap on the pipes, one sounds wrong, guess what.

Plain sight? I’ve found dope, cash and guns in flour canisters, in cereal boxes, inside a couch. You name it, its been used.

And with the proliferation of fiber optic cameras, places you couldn’t check 20 years ago are easy now.

More to follow.