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WATER PRESSURE LOSS DIAGNOSIS & REPAIR
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WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
This article 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.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
This article series describes various types of drinking water sources like wells, cisterns, dug wells, drilled wells, artesian wells and well and water pump equipment. We provide advice about what to do when things go wrong.
Readers of this document should also see Water Tank Types and before assuming that a water problem is due to the well itself, see Water pump and pressure tank repair diagnosis & cost an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost.
A variety of methods are used to install small-diameter water wells in areas where an adequate water supply is sufficiently close to the surface, where cost must be minimized, where well installation speed is important, and where there may be less concern for drinking water contamination from surface runoff. This article describes the two most common small diameter well methods, driven point wells and jetted wells.
Other small diameter well types include bored or augured wells, hydraulic percussion wells, cable tool percussion wells, bail down wells, and hydraulic rotary-drilled wells. All of these small diameter well methods have the advantage of comparatively low cost, rapid installation, and simplicity, and the risk of limited water availability and surface runoff contamination of the aquifer - considerations we explain in more detail below. 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.
As the UN FAO document explains:
How are driven point wells installed?
The driven point is then hammered into the soil, usually to a very shallow depth, perhaps 6' to 8' in depth, and usually in sandy soil or in other soil where a lot of water flows easily to enter the end of the pipe.
While special heavy-walled pipe and couplings are needed for the pipe to withstand the forces of being hammered into the ground (usually by a weight that is repeatedly lifted and dropped onto the upper pipe end), driven point wells are often home made or fabricated by a local well driller
The well pipe with attached point and screen is usually driven by a slide hammer much like those used to drive steel fenceposts. A larger diameter pipe that will slide over the upper end of the well pipe is raised and dropped repeatedly to drive the well point into the soil. A screw-on pipe cap protects the upper end of the driven well pipe from damage. See the UN FAO sketch of a well driving apparatus (below left).
Alternatively the driving pipe may slide inside the well pipe as shown in our second UN FAO drawing (below-right). Two additional well point driving schemes are included in the illustrations available in the full UN document "Small Diameter Wells", Natural Resources Management & Environment Department, Food and Agriculture Organization of the United Nations, FAO Corporate Document Repository - Self-Help Wells. That excellent resource includes other well boring and drilling methods as well as techniques for dealing with problems such as retrieving broken well pipes or tools dropped into a well. (Local copy provided).
The upper end of the driven point pipe is usually connected to a one line jet pump which "sucks" water out of the ground. In areas of very wet sandy soil a driven point well may be able to produce a barely functional water supply quantity (by modern standards)
Driven point well water quantity - well yield capacity: Compared with a modern 6" steel casing drilled well, a driven point well installed to the same depth in an aquifer of the same yield capability (the cone of depression is the same), a larger diameter well will yield 1.6 times that of a small diameter well according to United Nations documents on water wells.
Driven point wells often have rapid reduction in water flow rate, depending on the type of soil into which the driven point was inserted. For this reason multiple driven point wells may be connected together to obtain an adequate water supply.
If the water quality from a driven point small diameter well is adequate but the water quantity is not, it may be possible to improve well yield by driving the point deeper into the soil. In general, well yield increases more by increasing well depth than by increasing the well diameter.
Driven point well sanitation and water quality: Even in areas of sandy soils where these shallow wells are frequently used, water quality is questionable as surface contaminants easily enter the water supply, and water quantity is unreliable in areas where the water passage holes in the driven point become easily clogged with debris.
Our clients who have bought homes serviced by a driven point well have ultimately converted to a modern drilled well for better water quantity and for a more sanitary water supply.
Driven point wells are also used in soil de-watering applications during construction and in some locations driven point wells are used to test for water in soils before drilling or digging a higher capacity well.
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 downinto 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.
What is a wash well? Jetted wells are similar to driven point wells in that a pipe is forced into the soil and connected (most often) to a single line jet pump. In some communities the term "wash well" is used for this water source, as suggested by New Hampshire reader Jack Allen.
How are jetted wells or wash wells installed? In either case, the pipe that is to be used to obtain water is forced into the soil using water at high pressure (40 psi for sandy soils, up to 150 psi for clay or gravel) from an existing water source.
The illustration (left) is from UN document "Small Diameter Wells"
Unlike a driven point well, however, the pipe used in combination with water to force an opening into the ground (the jetting tube) may be a temporary one (the jetting casing is removed from the ground after the jetting process is complete, followed by the insertion of a new casing and casing end screen) or it may be permanent (left in the ground at the end of the jetting process, jacked up just enough to accommodate a well screen lowered inside the casing to its bottom end).
An alternative jetted well process permits soil material to actually be removed from the well opening during the jetting process (soil flows up from the bottom of the jetting casing around its outside surface.
Water flowing from the tip of the jet dislocates soil sufficiently to permit the well pipe to be pushed into the ground. Using this process a jetted well (or wash well) may be driven deeper into the soil than a driven point well, and a jetted well may be driven through soils harder than those penetrated by a driven point well.
Check valves or foot valves in jetted wells: To avoid losing prime in a jetted well a check valve may be used at the lower end of the casing, above the well screen. This detail is important for a homeowner to know, because if a jetted well or wash well stops working the problem could be a failed check valve (or foot valve) rather than a loss of water in the aquifer.
Jetted well water capacity or well yield: In soils that contain large amounts of water, particularly in areas of gravel or sand, a jetted well or wash well may deliver good water flow or quantity.
Jetted well water sanitation: However the water quality questions that apply to a driven point well might need to be considered for a jetted well too: a well of this design has little protection from unsanitary groundwater compared with a steel-casing drilled-well that is cut into water bearing rock and that is sealed against surface water entry. We suspect that a jetted well installed using the alternative process that actually removes material from the well opening by flowing soil to the surface along the outside of the well casing may be more prone to surface water leaking into the well and its aquifer.
Mr. Allen points out that when well repair or service is required for a jetted well, the homeowner will need to contact a company who is familiar with this particular well type.
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