InspectAPedia®   -   Search InspectApedia

Schematic of a drilled well (C) Carson Dunlop AssociatesWater Well Bore Alignment & Plumbness
Standards for straightness of Well Bores

  • POST a QUESTION or COMMENT about installing, diagnosing, repairing, or replacing all of the components and controls for private well water systems.

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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Water Well Bore Alignment & Plumbness

Photograph of  a modern steel well casing and cap extending properly above grade level and properly capped. You can see from
the gray plastic conduit that electrical wires enter the well, informing you that this well is served by an in-well submersible well pump.

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

Long submersible well pump would bind if the well bore is too irregular (C) Daniel Friedman at InspectApedia.com

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



...

Continue reading at DRILLED WELLS, STEEL CASINGS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

Suggested citation for this web page

WELL BORE ALIGNMENT PLUMBNESS STRAIGHTNESS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification
when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Comment Form is loading comments...

Citations & References

In addition to any citations in the article above, a full list is available on request.



ADVERTISEMENT