Just wondering how a well man knows when to stop drilling & call it "good"?
If, for example, you hit water at 30 feet why drill farther? Do you punch into additional aquifers as you drill deeper?

 

30 ft. would be one shallow well.
You also need storage area or the pump will drain it dry in no time.
At 30 ft. your still subject to surface water contamination.
A real well driller does what's called a pump test.
Well flow test, well yield test, well draw down test procedure: How to Test Well Flow Rate & Well Water Quantity

 

Where we are located, in addition to the scientific stuff, our drillers look for granite dust. Once they punch through solid granite, there are usually water filled pockets below them and water is pure and abundant. Here, in the mountains, however, if you live high, a 500' well isn't uncommon, but at a price Mine is 200' and never a problem and cool clear water.

At a former home, I had one drilled and was standing around watching, when the operator yelled to clear out. It was like an oil well you see on TV. Had plenty of water there

 

What did people do before drilling rigs? If there's no water above 50 feet I guess you moved.

Here in the Great Lake State you don't need to drill deep for water but wells still are drilled 100 feet or more. Why?

 

To get away from the contamination that might be in water at shallower depths.

 

I'd be curious to know how you keep the water you hit at 30 from entering your 100 foot well.

 

That's one reason for the casing to go down 100 feet.

 

Optimal well depth is relative to the area. A competent local well driller will know where the best water is usually found. When I lived in fla, I could hit water on my property with a post hole digger Consistent water could be found at 25'-30' but the best water was between 80'-120' If you went to 150' or deeper you would likely hit sulfur water While this was true of my property - 50 mile away could be entirely different.

I remember a story in the news 25 or so yrs ago where they found all kinds of dangerous chemicals in a well near Disney World. Since I also had a well in central fla I followed the story intently ..... until they revealed that the well was only 7' deep!

 

If you think that being surrounded by water means that it is universally and readily available, consier a trip north through the Great Lakes state. First stop, Milan, a mere 35 miles north of the border. The residential water delivery in that area is booming, coutesy of local authorities allowing sand and gravel pits to go deeper and deeper, until area wells dried up. That was a good number of years ago, and most if not all of the wells have returned, but many with an unacceptable sulphur content. North to Ann Arbor; well, just google Gelman and dioxane. How about the tri-city area, Saginaw, Bay City, and Midland. It's improving, quite dramatically by some measures, but think Dow, Chevrolet Gray Iron, etc., then look at the fishing reports for the Titabawassee River and Saginaw Bay. There were many years that you definitely did not want to take your catch home. How about Alabaster, a bit north and east of Standish? Go down any where from 20 to 200', depending on where the white rock shelf is under you, continue through the rock (very costly), and you can have some of the best water there is. You can also find many productive veins above the shelf, and because a lot of it is sand, a lot of them are even hand driven. Not bad tasting water, usually, but just plan to replace your faucets, toilet valves, etc. on a regular basis. North to St. Ignace. Well, not bad water at all, afterall, that is God's country, but there are many places where there is barely enough dirt to grow grass on top of the solid granite and other rocks. Sorry if too long, but point is that there are a lot of reasons that you can't simply stick a pipe in the ground and get water, and, even if you are so lucky, you can't always accept water as, well, water.

 

I see this mentioned a lot and I understand that drilling past where you hit water gives you a reserve supply but I thought water exists at many levels so cross- "contamination" would have to occur. Or is there something I'm missing in my understanding?
At my old cottage up north (just sold) the water at 30 feet from a hand-driven pipe is the best tasting I have ever drank--including bottled. The new cottage a block away has a well at the same depth but isn't quite as good tasting.
Neighbors whose hand-driven wells have failed have had to drill deeper per current code and their water is smelly with iron, sulfur and minerals.

When drilling the well don't they actually smell or taste what's coming out?
If the casing seals up any aquifers it passes through, then where does that storage capacity Joe mentioned come from?