I thought all residential wells had casings, or pipes lowered into the boreholes to keep them from collapsing. But a friend who is usually right about such things says only the top few feet are cased. A web search leaves the question unclear. I have found statements that when the well enters solid rock, the casing is no longer needed, but am mystified how only some sections can be cased in a well that penetrates multiple interleaved layers of rock and gravel.
The well at my house is Fifty-five ft. deep in to Mother Earth, it is cased all the way down.
At my fathers old place the well is hand dug to Thirty+ feet. No casing, lots of rocks make up the insides. This well is much larger around than the drilled/driven well at home.
These are things I know YMMV
I carefully watched the driller put in my well, asking questions frequently. Though the well is fairly shallow – only 200 feet – there is no casing. The pipe is 2-inch schedule 40 PVC with a 20-foot strainer section (identical pipe with thin, slotted perforations) in the water-bearing sand at the bottom.
Since the water table is only slightly below ground surface, the pick-up pipe from the pump is only one 20-foot joint of 1-inch pipe with a collar on top, dropped down inside the 2-inch pipe. So I guess you could consider the 200 feet of 2-inch pipe to be both casing and production line.
The well is cemented in from ground level down several feet (I don’t know how many - probably about ten). The purpose of the cement, in addition to stabilizing the well pipe, is to prevent ground water from going down the well hole into the aquifer. I understand it’s required by law.
Perhaps some of the confusion is due to terminology. As far as I know, in oil wells there is a casing, or outer pipe, and a production line, or inner pipe (and possibly more). In my water well there is only one pipe that goes to the bottom. There would have to be at least one pipe down a well to prevent soil seepage and water from other sands or strata getting into the well. I certainly wouldn’t want to drink water from a well that was produced only through the bore hole.
Hmmm - well, maybe terminology is part of the problem.
I know there is a pump at the bottom of my well, and what looks like about 3/4" ID stiff black plastic tubing going down to it, and also what looks like 3-conductor cable running along with the plastic tubing, and there is steel pipe of about 4" ID that comes out of the ground and has a removable lid so I can look down. I also understand that when my pump goes bad I’ll have to pull it up by the tubing and cable.
What I want to know is whether there is a larger diameter pipe keeping the hole open, such that the pump and tubing and wire are hanging inside said larger pipe. This is certainly true at the very top where I can see. Or, alternately, are they hanging in earth and rock and gravel, except for the top few feet? This is what is surprising but true according to my source who is almost never wrong.
Napier, I’m a bit outside my area of expertise here, but I’m GUESSING that your submersible pump is at the bottom of a pipe, and that the pipe is perforated somewhere near the bottom to allow water in the aquifer to enter.
My suggestion is that you look in the yellow pages of the phone book under “Water Well Drilling and Service.” I’m sure you can find a professional who would be happy to give you an accurate answer. For free. And even if s/he is a little grouchy about it, the information should still be good.
The well we have is ~350’ or so down. The first 50’ of the tube is in glacial till/loam, and is cased with a 6" steel pipe. Where the bedrock begins (at the 50’ level), the hole is 4" diameter and does not have a steel pipe lining it. The weight of the 6" pipe pushing down on the bedrock effectively seals off the hole, and the hole through the rock is cased by the rock itself (or so the drilling contractor told us).
I wound say it depends on what the well driller found. If the area is such that it is loose material (loam, sand, gravel) then a casing will have to be installed and the bottom of the pipe will have holes in it to let in water. If it goes into rock then the only way water can travel is through fractures (sometimes explosives are used to create more fractures). If this is the case I would wag that the casing is the rock itself and the fractures will drip water into the well.
When I say drip - it will most likely run along the sides, join up with other drips.