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Hand dug well under construction (C) A Starkman D Friedman Hand Dug Water Well Water Potability
Is the well water ok to drink?

  • POST a QUESTION or COMMENT about determining the quality & safety of well water from a hand dug well: how do we test & protect the hand dug well water for & from contamination?

Potability / safety of water from a hand dug well:

This article series offers advice for Hand Dug Water Wells and the sanitation and maintenance concerns with this water supply type.

This article describes the process of digging a well to provide usable water and the steps taken to make the well safe and sanitary. We include both technical advice and a description of the practical problems that one must encounter and overcome in providing usable water in an area where public water supply is absent or limited.

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

Checking the Potability of Water from a Dug Well

Boiling water to make it safe to drink (C) Daniel Friedman Alvin Starkman M.A., LL.B., Casa Machaya, Oaxaca Bed and Breakfast. The article author, Alan Starkman writes here about well digging from a lay person's perspective.

Also see DUG WELL SANITATION PROTECTION for more about safe drinking water from hand dug wells.

[Click to enlarge any image]

This article series offers advice for Hand Dug Water Wells and the sanitation and maintenance concerns with this water supply type.

This article describes the process of digging a well to provide usable water and the steps taken to make the well safe and sanitary.

We include both technical advice and a description of the practical problems that one must encounter and overcome in providing usable water in an area where public water supply is absent or limited. The article author, Alan Starkman is a retired Toronto attorney who operates the Casa Machaya bed and breakfast in Oaxaca Mexico.

Mr. Starkman has written more than 90 articles about life and cultural traditions in Oaxaca, Mexico, and writes here about well digging from a lay person's perspective.

I had the water from our new dug well tested at a local university, but after a couple of rains and no cover on it, and it came back with some e-coli, apparently no surprise.

The engineer said to come back after the tabique circle (partition wall circle) and arc are done, the top is on, and all the crap at the bottom has been removed and the rest has had a few days to settle so we can get a more accurate readying of more or less pure water without drain-off contaminants.

She said she'd then test again, and we would put in some bleach, and test again to see the potential.  She is confident that the water will be drinkable (not that we will drink it, but it certainly suggests your contention  is right on that it should be kept isolated from the regular cistern water).

The best of all is that she's prepared to work with me in term of recommending chemicals, people to clean and filter, etc.  I already have a pump guy for a submersible, and it's just a matter of determining how many hp, you'd think a simple task, but not so down here.

Water Quality: Technical Notes on Dug Well Sanitation

Well chlorinator (C) Daniel FriedmanIt is almost impossible to keep a dug well sanitary - dug wells are usually completely open to surface and ground water runoff.

You can shock the well, but if you are not going to drill a modern sanitary well (costly) you will need to install water treatment equipment to sanitize the water - after testing to see what contaminants besides bacteria are present.

Shocking a dug well to try to make the water potable or safe to drink is usually pointless because at any moment after the test contaminants can easily enter the well from surface runoff, groundwater, or at other points such as at a hand pump.

See WELL CHLORINATION SHOCKING PROCEDURE.

If nonetheless someone insists on shocking the well, it is important to wait, on letting the dug well "settle" before further testing, also see our warnings

at FAILED WATER TESTS - WHEN to RE-TEST.

Our photo (left) shows a typical residential well water chlorination system.

If the well water is used for irrigation, such as watering plants, and possibly for filling a swimming pool (slowly or you'll run the well dry -

see How Much Water Will a Dug Well Deliver?) - watch out whose water will be disinfected by the pool treatment equipment, using the Dug well may be fine.

But if the dug well water is to be used for drinking - that is, for a potable water supply - water treatment equipment will be needed.

Before you can choose what water treatment system is appropriate, it is important to test the water for both sanitation issues (bacteria, chemical contaminants) as well as aesthetic concerns (sediment, odors, taste).

 

Watch out: don't mix water from an un-sanitary source with potable or sanitary drinking water. Doing so risks cross-contamination of the entire plumbing system. If your property includes both potable and non-potable water supplies, be sure to keep their piping and storage facilities completely isolated from one another.

Looking Ahead to Part II of Digging a Well in Oaxaca

In my next and final installment, I deal with issues such as flow rate, biological analysis, decorative brickwork and custom iron cover, ongoing issues relating to structural integrity, and matters such as pumps and piping, the additional cistern, and whatevr.

 

Well Water Safety Resources & Research

 


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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: lab says my dug well coliform level is "about what you'd expect" - is it pointless to treat it?

Thanks for your article about bacteria counts in drinking water. You thought it was pointless to treat a hand dug well. I have two on my property that both have houses and so no direct surface water gets into them. After a rain the one has water seeping into the wall at about seven feet down; the other doesn't have visible water entering in until more like fifteen feet down.

I've had both wells tested and requested coliform counts that the lab said were what you'd expect from spring water. Being under shelter and all do you still think it would be pointless to treat these wells in an attempt to eliminate all coliform? Thanks - Anonymous by private email 2020/04/23

Moderator reply: new water is constantly entering the well; treating just what's in the well won't work.

In my experience and opinion, yes in a sense. There's no advantage to treating just the water that's inside any well, but especially a dug well since new water is entering the well whenever any water is removed.

Therefore, even if we treated the water in a dug well and tested it and found it sanitary, there's no assurance that hours later the water is in the same sanitary condition.

For that reason it makes more sense to install a water treatment system that disinfects all water from the well at the time it is taken out for use in cooking or drinking. That might be a combination of filter and UV and/or disinfection by chlorine injection.

Reader follow-up:

Is it that after a certain depth the dirt and groundwater become mostly coliform free? Do you know about how deep that typically is?

Moderator reply: It depends ...

The depth at which we don't expect to find coliform is not a single "right" number. That depth is site-specific and is a factor of depth, soil properties, distance to contaminants (varying by geographic area)

But in general, a drilled well is sealed against surface water entry and also against high groundwater entry.

So yes, the deeper aquifer is more-likely to not-contain common contaminants that arise on or near the ground surface.

However some wells, even deep wells, can tap a contaminated water source.

Reader follow-up: 73 colonies per 100ml. and no E.coli.

The reading from the one well was 73 colonies per 100ml. and no E.coli. Does that speak anything to you? That was what the lab considered typical of spring water. I believe that water originates from the wooded hill across the street where there is a spring.

We have a lot of red clay high iron soil. I did a more comprehensive water test one time and the only concern other than the coliform was a high corrosive factor, I forget what they called it now, but it had to do with how much scale would deposit on metal objects. Thanks-

Moderator reply: difference between Total Coliforms and E-Coli tests: indicators vs. contaminants

The EPA Maximum Contaminant Level (MCL) for coliform bacteria in drinking water is zero (or no) total coliform per 100 ml of water.

"EPA considers total coliforms a useful indicator of other pathogens for drinking water. Total coliforms are used to determine the adequacy of water treatment and the integrity of the distribution system. " - U.S. EPA, "Revised Total Coliform Rule" (RTCR) published in the Federal Registry, 13 February 2013 (78 FR 10269).

Re-stating this in more detail we have

A water sample is unsafe, present or total coliform positive if coliform bacteria are found in the sample. Generally coliforms are bacteria that are not harmful and are naturally present in the environment. They are used as an indicator that other, potentially harmful, fecal bacteria (indicated by the E. coli species) could be present.

If any routine or repeat sample is total coliform positive, the system (i.e., the lab) must further analyze that sample to determine if E. coli are present.

The presence of coliform bacteria in tap water suggests that there could be a problem with existing equipment or treatment systems, contamination of the source water or a breach in the distribution system that could introduce E. coli contamination. - U.S. EPA retrieved 2020/09/20 original source: https://www.epa.gov/region8-waterops/addressing-total-coliform-positive-or-ecoli-positive-sample-results-epa-region-8

What does this mean? Keep in mind that testing for bacteria ONLY is testing for bacteria; it is not a test for any other contaminants that might be in drinking water.

IN sum, "Total Coliforms" as a group are in general not harmful to humans, with some exceptions. But total coliform is an indicator of what's going on with your well.

The presence of non-coliform bacteria pretty much tells us that surface water and runoff are in the water source or well or spring.

That in turn means that anything - any contaminant - that's on the surface can leak into your water source. In this respect, a coliform test is a screening test.

That is to say you did not test for other common contaminants like pesticides, nitrites, nitrates, etc. nor did you test for specific contaminants that are at particular liklihood at your property - something often derived from a site history.

For example one of my clients found that the history of his property included a metal plating business. His water and soil were contaminated with cadmium. Without knowing about the plating business he'd never have thought to have that test performed.


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