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Driven point well or jetted well yield restoration or improvement: how to restore the water flow from a driven point or small diameter jetted water well.
This article series explains installing, diagnosing, and repairing small diameter water wells including driven point wells, wash wells, and jetted wells, three types of water sources that may be used where water is close to the ground surface and a well pipe or point can be driven into the soil mechanically or by using hydrojetting. We include an excellent UN FAO small diameter well document reference that will be helpful to those needing to construct a water well in areas where water is close to the ground surface and money or other resources are limited.
Restoring the Yield of a Driven Point Well - how can I get my water back?
Reader Question: My Driven Well Point is Clogged - Do I Have to Drive a New Well?
The well digger tells me that I have a clogged point on my driven point well and it is not letting enough water in the well pipe to the pump.
My water is good and the water pressure is awesome for about 2 minutes then it goes down to nothing. I wait about 30 seconds and it comes back.
Bad thing is the well digger hand drove this well for me about 4 years ago. Now he tells me the point is clogged not letting enough water in fast enough.
He borrowed my 22 caliber rifle and shot about 7 rounds down into the well, but nothing happened.
I am being told by him that we need to drill another well right next to the old one.
Needless to say I am not a happy camper. This well is on an extra lot I have that I use to grow a garden and store my boat in the winter. The only thing I use the water for is watering the garden.
Is there another fix for this thing? A friend says we could attach an air compressor to the pipe and shoot about 100lbs down there, or we could
Get some pipe and drive it thru the point on the bottom to open it up.
The well digger says when he drilled the first one that he drove that point in there so hard that would never come back up out of there.
Reply: Dynamite or Shooting a Rifle Down the Well are Bad Ideas
What you describe is loss of well yield, or loss of water flow into the driven point or lower section of the well pipe. This could be caused by the well itself going dry or going to a very reduced water flow, but the most common cause of this problem is just what your well driller says, a clogged well point.
While we know folks who used to drop dynamite down drilled or hand dug wells to try to correct the yield, neither dynamite nor shooting a rifle down into a water well are a recommended procedure.
If the well point is indeed clogged you would need to pull up the well piping and replace the point, then re-drive the well, or simply drive a new point down in the same area.
But first You could try sending high pressure water or even high pressure air backwards through the pipe to see if you can de-clog the point, but we're not optimistic. Also, some driven point wells also use a well screen that is at the top of the well pipe. Take a look at your well piping to see if there are any screens or fittings above ground that can be disassembled, inspected for evidence of clogging, and then cleaned or replaced.
Don't try driving an inner pipe through the well piping - you'll just break the point or jam things up worse.
Follow-up: Success in Restoring Driven Point Well Water Flow
We used an air compressor with about 120 lbs of constant pressure to blow air back down the well pipe. We attached a tire valve to a coupler which we attached to the well pipe to make it easy to hook up the air compressor to the piping, then we blew high pressure air into the well for about 10 minutes.
We then took off the well pipe check valve, which seems to be all plastic, and ran water thru it along with some WD40 to be sure that there was no problem with a clogged check valve itself.
Then we put everything back together and turned on the well pump. We had some pretty rusty water in the beginning but it cleared up, and I had beautiful pressure!!! My original problem was that the water pressure would not last, trickle down to nothing then build again.
I sprayed the garden hose for a good 20 minutes without missing a beat.
This process had restored water flow by clearing a clogged driven point on the well pipe bottom. The fact that flow is now good and continuous argues that indeed the problem was the clogged driven point, not a loss of water flow in the ground around the point. What we don't know is how successfully we've de-clogged the point, how many of its clogged openings we unblocked, and how long this repair will last, but it's a great attempt that might be totally successful.
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Thanks to Jack Allen, Brookline, NH for pointing out our omission of wash wells from the discussion of water source types and who also provided the small diameter well reference below for well drilling information from the United Nations. 31 July 2009
"Small Diameter Wells", Natural Resources Management & Environment Department, Food and Agriculture Organization of the United Nations, FAO Corporate Document Repository - Self-Help Wells - see http://www.fao.org/docrep/X5567E/x5567e05.htm This article has a nice section on well pipe or dropped tool fishing tools (WELL RETRIEVAL TOOLS) at its end. If a tool is dropped into a well or if a section of well piping becomes disconnected and drops into a well, special devices can be lowered into the well to attempt to grasp or hook the lost object (or pipe) to pull it back out of the well. See http://www.fao.org/docrep/X5567E/x5567e05.htm#4.11%20problem%20solving
This document describes the following types of small-diameter (hand-built) water wells: [Quoting] 4.1 Bored or augered wells - This method of excavation consists of shaving or cutting material from the bottom of the hole by the rotation of a cylindrical tool with one or more cutting lips. The process is quite analogous to boring a hole in wood or metal with an auger or drill. The excavated earth normally feeds upward and is contained in the body of the auger where it remains until the auger is emptied. The auger is both rotated and raised and lowered by means of a vertical shaft which extends upward from the auger to a convenient point above ground level from which it can be rotated. Rotation is frequently accomplished by human power applied to a handle attached to the vertical shaft. However, the auger may be driven by other power sources such as animal or engine power. In this case, the power source drives a horizontal ring gear. Two projections extending upward from the ring gear drive a bar known as a "kelly" which lies across a diameter of the ring. A square section of the auger shaft fits through a square hole at the centre of the kelly bar which causes the auger shaft to rotate with the kelly bar while allowing it vertical freedom.
4.2 Driven wells - The driven well consists of a pointed perforated pipe or a pipe with a pointed well screen attached which has been driven into an aquifer. The pipe with pointed well screen is driven into place in much the same way a nail is driven into wood. Normally special pipe with thick walls and specially designed couplings are used to resist the driving forces. Under suitable conditions this method can yield a finished well in a very short time. While the well diameter is normally small and the yield relatively low, a number of driven wells may be coupled together and pumped with a single pump. Because driven wells are quick to construct, they may be used as a temporary source of water and then be pulled up when no longer needed. Driven well points may be installed and used for dewatering an excavation during construction. Unlike other well construction methods, material is merely forced aside and not excavated by the driving process. This means that little is learned about the material through which the well pipe passes. This kind of well can, however, be used for exploratory purposes to determine static water level and rate of inflow versus drawdown. Hard formations cannot be penetrated by this process. Barring impermeable strata the depth to which such a well can be driven depends on the build-up of friction between the well pipe and the material penetrated and the transmission of the force of the driver down the length of pipe. Twenty-five to thirty metres (80-100 feet) would probably be a maximum. A driven well point might be employed to finish a hole which had been excavated down to the water table by some other method such as an auger.
4.3 Jetted wells - This method makes use of a high velocity stream of water to excavate the hole and to carry the excavated material out of the hole. It therefore requires some type of pump, either motor or hand-powered, of reasonable capacity, as well as a supply of water. It is possible to separate the water and the excavated material in a settling pool or tank and to reuse the water, thus minimizing the quantity required. Since this method depends on the erosive action of water, it is obvious that extremely hard materials cannot be penetrated. However, semi-hard materials may be penetrated by a combination of hydraulic and percussion effects. This is accomplished by raising and dropping a chisel-edged jetting bit. Coarse materials such as gravel require a greater water velocity to move them vertically out of the hole than do finer materials. However, very fine, hard packed materials such as clays require a high water velocity to dislodge them. Water pressure of 3 kg/cm2 (40 psi) for sand and 7-11 kg/cm2 (11-150 psi) for clay or gravel have been recommended. Under good conditions, drilling progress is very fast.
4.4 Hydraulic percussion (also hollow rod method) driven wells - In this method the hole is kept full of water and a combination of mechanical and hydraulic action do the excavating (Figure 17). A chisel-edged cutting bit is attached to the bottom of a string of drill pipe. The hollow bit has inlet ports a small distance above its cutting edge. During drilling the drill pipe is alternately raised and dropped. Pressure due to the impact of the cutting bit in the bottom of the hole and the inertia of the water cause a mixture of water and cuttings to enter the inlet ports of the cutting bit. This causes the already full drill pipe to overflow. A check valve in the cutting bit prevents the mixture of water and cuttings from flowing out of the ports when the drill stem is raised. The cuttings may be settled out from the water in a pool or barrel after the mixture overflows from the drill pipe and the water can then be recycled. Hydraulic percussion is limited to drilling through relatively fine materials, since coarse materials will not rise to the surface through the drill pipe. This method has been used to depths of more than 900 metres (3 000 feet) in alluvial areas where neither hard formations nor coarse materials were encountered.
4.5 Percussion (also cable tool method) driven wells - This method consists of repeatedly raising and dropping a chisel-edged bit to break loose and pulverize material from the bottom of the hole. A small amount of water is kept in the hole, so that the excavated material will be mixed with it to form a slurry. Periodically the percussion bit is removed, and a bailer is lowered to remove the slurry containing the excavated material. The bailer or bailing bucket consists of a tube with a check valve at the bottom and a bail for attaching a cable or rope to the top. When it has been raised and dropped a number of times to fill it with the slurry it is brought to the surface for emptying. Bailing is repeated until the hole has been adequately cleaned, at which time drilling is resumed; drilling and bailing are then alternated. If the hole is unstable, casing is lowered and the driving of casing is alternated with the other two processes. In loose granular material, such as sand, bailing alone may be sufficient to remove the material from the bottom of the hole and allow the casing to be sunk. A heavy bailer with a cutting edge at its lower end, known as a "mud scow" is used for this purpose.
4.6 Hydraulic rotary drilled wells - This method employs a drilling bit at the bottom of a stem of rotating drill pipe. Cuttings are removed by pumping water or a mixture of water and various clays down through the drill stem. This "mud" entrains the cuttings and carries them up through the annular space between the drill pipe and the wall of the hole. When they reach ground level, the cuttings can be settled out in a small pond and the "mud" re circulated. If the reverse flow path is used ("mud" pumped to the surface through the hollow drill pipe) the system is called reverse rotary. The reverse rotary system allows larger particles of cuttings to be brought to the surface, because the upward flow velocity inside the pipe is greater than that through the annular space, due to the smaller flow cross section inside the pipe.
Thanks to reader Lloyd McVey at AKR for discussing using compressed air to restore water flow in a driven point well, July 2010
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