Any Well Experts?

I got an well on my property it's OLD, like brick lined kind. I'm not sure if it hits the aquifer of if it's just rain water from roof or run off. It's 30 feet deep and about 24 feet full. I haven't tested for anything thus far I'm just feeling the idea out. My concerns are contaminants; roofing material, feces, pathogens, insect larvae etc etc... If they are present wouldn't they either be at the top or the very bottom? Bacteria and pathogens are the exception of this I'm thinking, but chemicals and solids should be separated according to weight correct? Any hydrologists' around...? Or has anyone used a older type well for supplying hydro applications?

I just keep thinking about the House episode where dude almost dies from pigeon shit getting in his water supply for his plants. Tho, got no flying rats round here

you could get one of those kits to take a sample and send it to a lab to get it analyzed. i think there are ones for like $25 or so.

It's probably going to come to that. I was just hoping someone might have some exp with them before I start running vials for testing. It's the pathegons that I really wonder about, not sure if the reg test checks for that...