Water well bores or drilled well casings need to be straight and more-or-less plumb. A bore that is not straight may not be able to have its pump installed or may cause vibration and failure of some well pump types.

Here we list standards and procedures for assuring a properly straight and sufficiently plumb drilled well bore or casing and we explain why those parameters are important.

These water, well, and water supply equipment articles answer inspection, diagnosis, and repair questions about the building water supply sources and equipment including water testing, water piping, water pumps, water wells, & water tanks.

Page top illustration courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing firm.

Water Well Bore Alignment & Plumbness

Question: deep well deviation limit from vertical/plumbline

2020/07/05 Anon by private email said:

What is deep well deviation limit from vertical / plumbline ?

Any material for deviation measurement please share. - Anon, Lahore, Pakistan

[Click to enlarge any image]

Moderator reply: Drift or plumbness vs Alignment of water wells

Ahmed

Thank you for asking a very helpful question; I will add a section to our article above, in which I will list standards for water well bore plumbness and alignment. Meanwhile one of my preferred sources on water well bore or casing alignment and plumbness, because of its clear and direct language is the following:

Drift or plumbness is the amount a given borehole deviates from true vertical. Alignment is the measure of straightness, or conversely the lack of excessive twists or doglegs.

A well can be straight but not plumb, but a perfectly plumb well will always be straight.

Alignment is the more important factor in a well, since a pump (particularly turbines) cannot be installed if the well is crooked beyond a certain amount.

Lack of plumbness by itself does not affect pump installation and only at extremes may impact pump life and operation; therefore, insufficient plumbness (or excessive drift) is rarely a problem encountered in modern well construction.

B. STANDARDS.

The AWWA standard allows a drift deviation of two/thirds the well's inside diameter per one hundred feet of depth.

The EPA standard is a deviation from plumbness of one degree per fifty feet of depth (Johnson, Groundwater and Wells 2d. page 333).

It is not uncommon, however, to see requirements as tight as three inches per hundred feet in recent projects.

Note that the problem with each of these standards is that a well which is sufficiently straight to accept the pump may fail the test.

Conversely, a well can meet the drift standard yet still have a tight enough bend in the casing to prevent the installation of the pump.

-source: Indiana State Department of Health cited below.

Reader follow-up:

The AWWA standard allows a drift deviation of two/thirds the well's inside diameter per one hundred feet of depth.

If a well ( 18 inch inner Dia casingis) is 250 ft deep then does it mean according to AWWA standards the allowable deviation is 30 inch??? I have to check 250 ft casing (18 inch) for pump lowering.
Considering 2/3 of inner Dia per hundred ft.

Moderator reply:

I make it .66 x 18 = 11.9 inches spread uniformly over 100 ft.

Do you agree?

Reader follow-up:

Sure I fully agree. Extending the same for 300 ft

Would it be. 66*18*3=36 inch approximately? Almost 2.5 ft. Allowable deviation?

It is a big value ...so I want to ask is this standard valid for 300 ft. ?

Moderator reply: acceptable well bore alignment variation must be distributed over bore depth not concentrated in one spot

Above: long, rigid submersible pumps and well piping, San Miguel de Allende, Guanajuato, Mexico.

[Click to enlarge any image]

The blue submersible pump shown here was bolted to large-diameter galvanized iron pipe and certainly would have jammed if being forced down a drilled well casing that was out of alignment by greater than the recommended standards we discuss here.

I think that's right (keep in mind I'm not a well engineer) - but what's critical is the distribution of the variance.

That deviation, to be acceptable, would have to be spread uniformly over the entire depth of the well casing.

As I understand it, any bend that's sharper would be unacceptable.

You can't sneak in a sharper bend over a shorter distance and then pretend you've averaged it over the whole well depth.

To be clear, the issue isn't that a well casing is not straight or plumb, it's that if it's too out of plumb or too crooked over a too-short distance then the pump or piping will bind.

The Indiana DOH statement makes this objective clear while giving no number at all. But we need a number to make sense of the guideline. 

Watch out: also in my OPINION that the risk of binding up a pump in a well casing or bore also depends on the dimensions of the pump itself. As you probably know better than I, some pump models are much longer than others. 

2.6 Plumbness and Alignment Each drilled well should be tested for plumbness and alignment.

The bore of the hole should be suciently plumb and straight that the casing will not bind as it is installed.

The casing should be suciently plumb and straight that it will not interfere with installation and operation of the pump.

Water Well Bore or Casing Alignment & Plumbness Standards & Measurement Procedures

• AWWA, A100-15 WATER WELLS STANDARD, (Strawn 2019)
  
  Excerpt: Appendix D: Maximum allowable horizontal distance between the actual well centerline and a straight line representing the proposed pump centerline shall not exceed one-half of the difference between the inside diameter of the casing and the desired maximum outside diameter of the proposed pump to be installed.
• AWWA, A100-90: STANDARD FOR WATER WELLS [PDF] available at: https://www.awwa.org/Store/Product-Details/productId/18417
  
  Description:
  This standard covers the construction of water wells ranging in nominal diameter from 8 in. (200 mm) through 30 in. (750 mm). Certain minimum requirements are presented that can be incorporated by reference into the purchaser's specifications.
  
  This standard is intended for large municipal and industrial wells that are constructed using normal well-drilling techniques. Major topics covered are: investigation of geologic/hydrologic conditions and groundwater quality; construction; well casings; well screens; gravel pack; grouting and sealing; plumbness and alignment; well development; performance testing; well disinfection; water quality testing; and abandonment of test holes, partially completed wells, and completed wells.
  
  Appendices cover gravel pack installation methods, grouting and sealing methods of placement; plumbness and alignment procedure for testing; methods of measuring operating parameters during development, water sampling; factors influencing the duration of pumping test; abandonment of test holes, partially completed wells, and completed wells; geophysical bore-hole logs; types of wells; and collapse strength of well casing.
• Brooks, Andrew G., and Harry Wilson. "An improved method for computing wellbore position uncertainty and its application to collision and target intersection probability analysis." In European Petroleum Conference. Society of Petroleum Engineers, 1996.
• CGA. Article 400–WATER WELL DRIFT & ALIGNMENT TESTING [PDF] - Adopted by the CGA Board of Directors on April 11, 1992 - California Groundwater Association Website: www.groundh2o.org , retrieved 2020/07/05, original source: groundh2o.org/resources/Documents/article_400.pdf
• DePonty, Jersy D. , Shane P. DePinto , Grant S. Kornrumph , and Marvin F. Glotfelty, WATER WELL PLUMBNESS AND ALIGNMENT STANDARDS –
  ANALYSIS AND RECOMMENDATIONS FOR OPERATIONAL APPLICABILITY [PDF] - retrieved 2020/07/05 original source: http://azwwa.org/wp-content/uploads/2013/11/PA-article.pdf
  Excerpt:
  
  This study considered two common water well standards to evaluate plumbness and alignment criteria; the American Water Works Association (AWWA) Standard for Water Wells (A100-06) and the standard detailed in the Handbook of Ground Water Development (Roscoe Moss Company, 1990).
  
  The Environmental Protection Agency (EPA) plumbness standard of 1 degree of deviation per 50 feet is also common, but was not included in this study since it is much less stringent than the AWWA or Roscoe Moss standards, and was not applicable to the wells being evaluated.
  
  The AWWA standard is common in the water well industry and is widely used by municipalities, private utilities, industry and consultants.
  
  The Roscoe Moss standard provides the primary basis for the plumbness and alignment requirements used in the current SRP well drilling specification.
  
  Both of these standards are appropriate for large diameter water production wells, and are applicable to the use of line-shaft vertical turbine pumps.
• Drilling Today, "NECESSITY OF PLUMBNESS AND ALIGNMENT OF WATER WELLS" in Drilling Today, Drilling Today House, A-145, Lehri Marg, Shivpuri, Airport Road, Airport Road Sanganer, Jaipur 302011 INDIA 91 Telefax: +91 141 2793166, 2792336 Mobile: +91 9414 219 166, +91 9460 435 474 Visit:www.dthrotarydrilling.com Write us: drillingtoday@yahoo.com retrieved 2020/07/05 original source: https://www.dthrotarydrilling.com/Technical-paper/Alignment-Water-Wells/Necessity-Plumbness-Alignment-Water-Wells.html
  Excerpt:
  
  A borehole may be straight but not plumb, if the borehole is plumb it will be straight. In practice some tolerance of deviation is straightness and plumpness is permissible. In a conventional drilling a deviation from plumpness of 2/3rd the wells inside diameter per 100 ft (30.5 mts) of an anticipated pump setting is permissible, considering various difficulties of drilling in different types of formation.
  
  Out of two factors, the straightness of the bore hole is most important, because it gives an idea whether or not particular size of pump can be lowered up to the desired depth of a constructed well.
• Hossain, M. M., M. K. Rahman, and S. S. Rahman. "Hydraulic fracture initiation and propagation: roles of wellbore trajectory, perforation and stress regimes." Journal of Petroleum Science and Engineering 27, no. 3-4 (2000): 129-149.
• Indiana State Department of Health, RECOMMENDED STANDARDS for PRIVATE WATER WELLS - Section 2.6 PLUMBNESS & ALIGNMENT [PDF] - Indiana State Department of Health Environmental Public Health Division 100 N. Senate Ave., N855 Indianapolis, IN 46204 USA (317) 233-1325 retrieved 2020/07/05 original source: www.in.gov/isdh/23258.htm
  
  Excerpt:
  
  2.6 Plumbness and Alignment Each drilled well should be tested for plumbness and alignment.
  
  The bore of the hole should be suciently plumb and straight that the casing will not bind as it is installed.
  
  The casing should be suciently plumb and straight that it will not interfere with installation and operation of the pump.
• Knapp, Seth R. "Method and apparatus for straightening well bore holes." U.S. Patent 2,829,864, issued April 8, 1958.
• Mcneely, Jr Branch M. "Means for controlling directional deviations in a well bore." U.S. Patent 3,043,381, issued July 10, 1962.
• NGWA, NGWA-01-14 Water Well Construction Standard, National Ground Water Association 601 Dempsey Rd. Westerville, OH 43081 USA customerservice@ngwa.org (800) 551-7379 (614) 898-7791
• Proposed NGWA/ANSI WATER WELL CONSTRUCTION STANDARD [PDF] Ground Water Protection Council, Inc. 13308 N MacArthur Blvd Oklahoma City, OK 73142 405-516-4972 , retrieved 2020/07/05 original source: http://www.gwpc.org/sites/default/files/event-sessions/5a_McCray_Kevin_0.pdf
• Rafferty, Kevin. SPECIFICATION of WATER WELLS [PDF] ASHRAE Transactions 107, no. Pt 2 (2001).
  
  Excerpt: For larger wells or those using lineshaft pumps, a more sophisticated test involving a device for measuring deviation of the bore is necessary.
• Strawn, Jennifer, "Plumbness and Alignment, Do your wells meet the standard?" in Water Well Journal, January 22, 2019, Email: strawnj2@gmail.com.
  Excerpts:
  
  If you’re primarily drilling domestic wells or other small-diameter, shallow wells, it’s not likely a small deviation in plumbness or alignment will cause problems.
  
  However, on deep wells or wells to be equipped with lineshaft turbine pumps, the plumbness, straightness, and alignment of the well is extremely important to the operation of the pumping equipment.
  
  Plumbness is the horizontal deviation of the well centerline from a true vertical centerline. A well can be straight and not plumb.
  
  Alignment refers to horizontal deviation between the actual well centerline and a straight line.
  
  A well that is not plumb or is misaligned (the casing contains bends or “doglegs”) can put excess wear and tear on the pump.
  
  ... To test the well for plumbness, you’ll need to complete a plummet test. The plummet test uses a tool constructed of a rigid spindle with two truly round plates or rings at both ends spaced 1.25 times the inside diameter of the casing.
  
  The plates or rings should be ½-inch smaller than the inside diameter of the casing and have holes or some other way for water to pass through it as it is lowered into the well.
  
  The plumb line should be attached exactly in the center of the plummet, and the plummet should weigh enough that the plumb line is kept taut.
• Stow, George Raymond Snewin. "Modern Water-well Drilling Techniques In Use In The United Kingdom." Proceedings of the Institution of Civil Engineers 23, no. 1 (1962): 1-14.
• US EPA, MANUAL of WATER WELL CONSTRUCTION PRACTICES [PDF] U.S. Environmental Protection Agency,
• USFGS, POTABLE WATER SUPPLY WELLS [PDF] see 3.2.3.2 Test for Plumbness and Alignment,
• Wong, J., Han, L., Stewart, R.R., Bentley, L. and Bancroft, J., 2009. Geophysical well logs from a shallow test well and automatic determination of formation velocities from full-waveform sonic logs. CSEG Rec, 34, pp.21-30.
  Excerpt:
  
  The geophysical well logs presented in this study gave useful information regarding the near-surface geological and hydrogeological characteristics of the Paskapoo Formation at the Rothney Observatory site near Priddis, Alberta

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