Failed well test:

What to do when the well fails a potability or bacteria test.

Here we explain how to interpret and act on the results of drinking water or well water tests for various types of water contamination.

This series of articles explains many common water contamination tests for bacteria and other contaminants in water samples. We describe what to do about contaminated water, listing common corrective measures when water test results are unsatisfactory.

Common Water Contamination Tests for Bacteria Levels - Identifying Unsanitary Drinking Water

We include water testing and water correction measures warnings for home owners and especially for home buyers when certain conditions are encountered, with advice about what to do when these circumstances are encountered.

Various treatment methods for contaminated water are reviewed and the pros and cons of each are discussed.

Emergency drinking water needed? Basic water purification procedures that can be used in an emergency such as after a hurricane, flood, or earthquake are described

at DRINKING WATER - EMERGENCY PURIFICATION and

emergency sources of drinking water are described

at  DRINKING WATER EMERGENCY SOURCES.

If community or private wells are back in operating and providing water, do not assume that the water is sanitary and ok to drink until responsible authorities have said so. Even then, local water pipes in a building may be unsanitary and additional cleaning or disinfection may be needed.

See WELL CHLORINATION SHOCKING PROCEDURE and

See WATER TESTS for CONTAMINANTS for advice on using a private well for drinking water.

This document combines information from various sources including from the Dutches County NY health department, from Smith Laboratory in Hyde Park NY (914-229-6536), water test developer/suppliers, and other independent sources. Pending review corrections by these sources, the author is responsible for the content which includes opinion and advice based on more than 40 years experience in the field.

Because water quality can have major effect on personal health, home owners and home buyers, & ASHI home inspectors should consult with their local health department before performing tests or taking corrective actions regarding water quality.

PA - Coliform Bacteria Test for Contamination in Water: Presence/Absence Test

This standard water test required by many banks, involves pouring use of a chemical Defined Substrate Technology (DST) reagent which produces a color change (or another signal, i.e. fluorescence), both indicating and confirming the presence of total coliform and E. Coli in a sample of drinking water. The test indicates either the presence or absence of this bacteria.

This test, used by most water test companies for real estate transactions does not produce a bacteria colony count. We order this procedure, or the lab will elect this procedure when the water sample is turbid (contains sediment or other material which precludes alternative test procedures).

The test is sensitive and specific for the detection of total coliform and E. coli at 1 CFU/100mL of sample in water samples with as many as 20,000 heterotrophic bacteria present per ml. This means that this test for coliform bacteria is not obscured by the presence of other bacteria in the water.

P/A Test results: if the test did not find an indication of a coliform bacteria problem the result will say "Less than 1" or if the lab reports carelessly, "Zero".

Accurate lab test reporting would be to say "below the limits of detection" of a given test, and then to specify the limits of detection used.

The acceptable level of bacteria in water varies by jurisdiction.

For example in some Canadian provinces a higher level of 10 CFU/100mL is permitted. These very slightly higher numbers are allowed because the opinion of health experts is that there is no measurable risk at those levels.

However generally world wide standards require a level of 0 total coliform and 0 E-coli detected per 100 ml. Details of those standards area

at COLIFORM STANDARDS for DRINKING WATER

M.F.T. - Coliform Bacteria Test for Contamination in Water: Membrane Filter Technique

This standard water "test" required by many banks, involves pouring 100 ml of water through a membrane filter. The bacteria present in the water are trapped on the surface of the filter. After an incubation period of 24 hours the coliform colonies present are counted. The count may not exceed 0 per 100 ml according to recently updated New York State Drinking Water Regulations. (MFT=Multiple tube Fermentation Test.)

MFT Test results: If the lab finds apparent unacceptable results with this general test for the presence of any bacteria, the revised NY State procedure requires the lab to measure for E-coli, by performing the MPN procedure as follow up.

This is because the presence of non-coliform bacteria present in the water can obscure the test and prevent counting E-coli. The NY State Sanitary Code has no standard for total bacteria count in water supply. The need to go to an MPN test often explains additional delay of up to a week beyond usual time for obtaining water test results.

MPN - Coliform Bacteria Test for Contamination in Water: MPN testing

This test is used when the water cannot be filtered due to turbidity, high iron, large amounts of sediment, or high non-coliform bacteria count. This test involves incubation of measured volumes of sample in liquid nutrients which favor the growth of any coliform bacteria present.

This is a statistical method of testing based on the number of positive tubes of media after 48 hours of incubation and 48 additional hours of confirmation.

MPN Test results: As of modified NY State procedures starting in 1991 a count of 0 indicates no coliform and water of satisfactory quality. (MPN=MilliPore Nutrient test.)

Interpreting Other Water Test Results

Examples of allowable limits (subject to change) for other tests are listed

at WATER CONTAMINANT LEVELS & LIMITS or select a topic from closely-related articles below, or see our complete ARTICLE INDEX below.

A Quick EPA Guide to Understanding Your Water Test Results

Have your well water tested for any possible contaminants in your area. Use a state-approved testing lab. (See below for sources of approved laboratories.)

Photo: because this steel well casing top was close to ground level and so loose that our inspection client could simply the whole well piping apparatus out of the ground we warned that there was also a risk of well water contamination.

Do not be surprised if a lot of substances are found and reported to you.

The amount of risk from a drinking water contaminant depends on the specific substance and the amount in the water. The health of the person also matters.

Some contaminant cause immediate and severe effects. It may take only one bacterium or virus to make a weak person sick.

Another person may not be affected. For very young children, taking in high levels of nitrate over a relatively short period of time can be very dangerous.

Many other contaminants pose a long-term or chronic threat to your health - a little bit consumed regularly over a long time could cause health problems such as trouble having children and other effects.

EPA drinking water rules for public water systems aim to protect people from both short and long term health hazards. The amounts of contaminants allowed are based on protecting people over a lifetime of drinking water. Public water systems are required to test their water regularly before delivery.

They also treat it so that it meets drinking water standards, notify customers if water does not meet standards and provide annual water quality reports.

Compare your well's test results to federal and state drinking water standards. (You can find these standards at www.epa.gov/safewater)

In some cases, the laboratory will give a very helpful explanation. But you may have to rely on other experts to aid you in understanding the results.

also see

• WATER CONSERVATION MEASURES
• WATER CONTAMINANT LEVELS & LIMITS
• TABLE of ALLOWABLE WATER CONTAMINANT LEVELS
• The state agency that licenses water-well contractors can help you understand your test results. It will also provide information on well construction and protection of your water supply.
  
  The agency is usually located in the state capital or other major city. It is often part of the department of health or environmental protection. Check the blue "government pages" of your local phone book or call the American Ground Water Trust at (614) 761- 2215 or the EPA website, www.epa.gov/safewater,for your licensing agency's phone number.
  
  Also, see STATE CERTIFICATION PROGRAMS CERTIFY LABORATORIES TO CONDUCT DRINKING WATER ANALYSES 2023 [PDF], US Environmental Protection Agency, retrieved 7/20/2023 , original source, https://www.epa.gov/system/files/documents/2023-03/state-cert-programs-certify-labs-to-conduct-drinking-water-analyses.pdf
  
• The local health department and agricultural agents can help you understand the test results. They will have information on any known threats to drinking water in your area. They can also give you suggestions about how to protect your well water.
• The state drinking water program can also help. You can compare your well's water to the state's standards for public water systems. State programs are usually located in the state capital or another major city.
  
  They are often part of the department of health or environmental regulation. Again, consult the blue "government pages" in your local phone book for the address and phone number or visit the EPA website, www.epa.gov/safewater.
• Previously, the Safe Drinking Water Hotline at (800) 426-4791, could help in many ways. The Hotline provided a listing of contaminants public water systems must test for. EPA also has copies of health advisories prepared for specific drinking water contaminants. The Hotline recording now refers you to their website, www.epa.gov/safewater or www.epa.gov/waterlabnetwork.
  

This article series on water contaminants describes types of activities in your area that can create threats to your water supply.

It also describes problems to look for and offers maintenance suggestions. Sources for more information and help are also listed. [Editing for clarity by DF are marked by brackets or italics] Initial Source of a portion of the above text: EPA 816-K-02-003 January 2002

Comment:

(June 20, 2011) Tommy D said:
I have been searching the web for information on how to read the results of my water test. This site has given me the most information on everything I've been looking for.

Reply:

Thanks Tommy. We also welcome questions & criticism - working together makes us smarter. - Ed.

Question: What does TDI represent?

(Feb 7, 2014) angela king said:
I just received results of a free water test from Home Depot.
TDI =161 Hardness = 15

What does TDI represent?

Reply: total dissolved ions

Angela,

If you search InspectApedia for our article titled "How to Measure the Hardness Water" you can read about the significance of that measurement; also see our articles about water softeners.

With NO INFORMATION I would offer a best guess that the report is indicating Total Dissolved Ions - which by addressing the ion level in water expresses its conductivity - a water quality measurement companion to hardness; And the Hardness number they gave is - well I just don't know as we don't know which hardness measurement they are reporting. Here's what I mean:

Unfortunately the fellows who wrote your "free" water test report gave you about what you paid for - a "hardness" number without telling us what terms they used nor the reference scale that leaves us a bit in the dark. It's like saying your water is as hard as a fuchimannouli.

Hardness is measured in either grains (in which 15 is quite hard) or in milligrams of minerals per liter, in which case 16.1-60 mg/L of minerals is only "slightly hard" - so I dunno.

And about TDI, there are multiple uses of that acronym as well. The World Health Organization (WHO) has a nice document on water chemistry. Quoting:

For most kinds of toxicity, it is believed that there is a dose below which no adverse effect will occur. For chemicals that give rise to such toxic effects, a tolerable daily intake (TDI). The TDI is an estimate of the amount of a substance in food and drinking-water,
expressed on a body weight basis (mg/kg or m g/kg of body weight), that can be ingested over a lifetime without appreciable health risk.

Guessing again and waving wildly, "TDI" has other meanings in health such as Toluene Diisocyanate - a harmful substance.

Perhaps your water report is missing the standard page that labs include that give definitions of the acronyms they are using as well as comparative measurement scales?

If you'd like to email us a copy of your report we may be able to comment more intelligently - use the CONTACT link found at page bottom or top

Mud, Dirt, or Solids Suspended in the Water Supply? TDS, TSS Measurements & Standards

Question: how to interpret my water test results

We complain that sometimes, especially after heavy rain, our well water has an unpleasant taste and odor.

My Culligan Man just performed a free water test for us. The results came back as

8 grains hard
.50 pmm of iron
334 TDS
6.5 ph

and a previous test for bacteria found coliform "present" - no count was performed, just a PA (Present/Absent) test was performed.

The company recommends a water treatment system that includes a UV light and an RO (Reverse Osmosis) treatment system that includes as well filters for sediment, carbon filters (odors and taste), and a post-carbon filter.

They say

In addition to E.coli, virus, algae, coliform, mold and others, our UV is effective against protozoa such as cryptosporidium and giardia lamlia. The Culligan UV effectively (99.99%)destroys these protozoan cysts. This is natural way of protecting your water without the addition of harmful chemicals.

Does this sound right to you?

Moderator reply: diagnose well water problems before installing water treatment equipment

About your previous bacteria test that found "bacteria present"

see BACTERIA LEVELS in WATER, INTERPRETATION

We have plenty of respect for Culligan and have used their system in homes for over fifty years. But in our OPINON your report and advice are a bit incomplete.

Your level of TDS is below WHO, US & Canadian standards but you might still improve the taste and odor of your water by treatment and filtration. First, in our OPINION you should assure that your well water is safe to drink, free from (or treated for) harmful bacteria AND checked for other common contaminants that might be present in your area and that have not been checked-for in your tests so far.

Here we suggest a bit more diagnosis of the source of your water quality issues, and we make a distinction between TDS - total dissolved solids and TSS - total suspended solids - that can in turn help decide just what water treatment steps your installer might recommend.

Further Water Testing & Well Inspection

It's common to install water treatment equipment in response to unsatisfactory water test results, but frankly, I'd prefer to check first to see if there's a mechanical problem that we should be fixing, such as a leaky buried well casing cap, leaks at the pitless adapter, or a hole or crack in well casing: all of which quickly admit surface water and contaminants into the well bore.

If we can fix something simple, in my OPINON that's preferable.

If inspection of the well plus water test results convince us that there is a persistent source of contaminants in our well water, then indeed water treatment, including filtration, disinfection, and perhaps softening or iron removal are needed.

I would not install ANY water treatment system before understanding just what contaminants are in the water supply.

You should have a bacteria test performed such as an MPN or MFT that gives an actual bacteria colony-forming-unit count, not just a P/A test. Without a count we don't know if your well's bacteria level is so high that you're drinking sewage, or if it's so low as to e easily treatable with a UV light system. UV light treatment can not successfully treat water that is high in sediment nor very high in bacteria.

At WATER QUALITY TEST CHOICES & WATER TEST FEES

Or you can choose one of the screening tests such as those described

at US FHA HUD WATER TESTING ADVICE

A Closer Look at Dissolved Solids in the Water Supply: TDS - Total Dissolved Solids

TDS or Total Dissolved Solids in water are solids small enough to pass through a filter with pore sizes equal or greater than 0.45 micrometers. TDS includes carbonate, bicarbonate, chloride, sulfate, phosphate, nitrate, calcium, magnesium, sodium, organic ions, and other ions. These reduce water clarity and they can explain an unpleasant water taste or may explain excessive water hardness (particularly if the water is high in calcium and/or magnesium).

U.S. EPA & Canadian TDS Standard:

In the U.S. the U.S. Environmental Protection Agency sets a secondary standard of 500 mg/L TDS in drinking water. In addition, beyond the "standard", the EPA warns that high TDS concentrations can produce laxative effects and can give an unpleasant mineral or metallic taste to water.

Canada also has set an equivalent standard for TDS:

An aesthetic objective of ≤500 mg/L has been established for total dissolved solids (TDS) in drinking water. At higher levels, excessive hardness, unpalatability, mineral deposition and corrosion may occur. At low levels, however, TDS contributes to the palatability of water.  - in Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – TOTAL DISSOLVED SOLIDS (TDS) [PDF] (1978) Canada Health, retrieved 2021/11/09 original source: https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-guideline-technical-document-total-dissolved-solids-tds.html

WHO TDS Standard

The palatability of drinking- water has been rated by panels of tasters in relation to its TDS level as follows: excellent, less than 300 mg/litre; good, between 300 and 600 mg/litre; fair, between 600 and 900 mg/litre; poor, between 900 and 1200 mg/litre; and unacceptable, greater than 1200 mg/litre (1).

- TOTAL DISSOLVED SOLIDS in DRINKING WATER [PDF] WHO/SDE/WSH/03.04/16, (2003) Background document for development of WHO Guidelines for Drinking-water Quality, retrieved 2021/11/09 original source: https://www.who.int/water_sanitation_health/dwq/chemicals/tds.pdf

Excerpting from the WHO document above:

Identity [of TDS]

Total dissolved solids (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water. The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogencarbonate, chloride, sulfate, and nitrate anions.

Organoleptic properties [of TDS]

The presence of dissolved solids in water may affect its taste (1).

The palatability of drinking water has been rated by panels of tasters in relation to its TDS level as follows: excellent, less than 300 mg/litre; good, between 300 and 600 mg/litre; fair, between 600 and 900 mg/litre; poor, between 900 and 1200 mg/litre; and unacceptable, greater than 1200 mg/litre (1).

Water with extremely low concentrations of TDS may also be unacceptable because of its flat, insipid taste.

...

TDS in water supplies originate from natural sources, sewage, urban and agricultural run-off, and industrial wastewater. Salts used for road de-icing can also contribute to the TDS loading of water supplies. 

...

No recent data on health effects associated with the ingestion of TDS in drinking-water appear to exist; however, associations between various health effects and hardness, rather than TDS content, have been investigated in many studies (see Hardness). In early studies, inverse relationships were reported between TDS concentrations in drinking water and the incidence of cancer (11), coronary heart disease (12), arteriosclerotic heart 2 disease (13), and cardiovascular disease (14,15). Total mortality rates were reported to be inversely correlated with TDS levels in drinking-water (15,16). 

...

Certain components of TDS, such as chlorides, sulfates, magnesium, calcium, and carbonates, affect corrosion or encrustation in water-distribution systems (4). High TDS levels (>500 mg/litre) result in excessive scaling in water pipes, water heaters, boilers, and household appliances such as kettles and steam irons (19). Such scaling can shorten the service life of these appliances (20). 

A Closer Look at Total Suspended Solids - TSS - in the Water Supply

In addition to looking at TDS - Total Dissolved Solids I'd want to look at TSS - Total Suspended Solids as that may indicate the level of filtration needed for other water treatment equipment to work.

Total Suspended Solids (TSS) are solids in water that can be trapped by a filter. TSS can include a wide variety of material, such as silt, decaying plant and animal matter, industrial wastes, and sewage. ... The U.S. Environmental Protection Agency sets a secondary standard of 500 mg/L TDS in drinking water.

- TDS & TSS TOTAL SUSPENDED SOLIDS in WATER QUALITY [PDF] SUNY Brockport Department of Earth Sciences, 350 New Campus Drive Brockport, NY 14420 USA, Web: https://www.brockport.edu/academics/earth_sciences/ Tel: (585) 395-2211 - retrieved 2021/11/09 original source: http://vortex.weather.brockport.edu/~jzollweg/oakorchard/docs/waterquality.pdf

UV Lights, Filtration, Other Water Treatments

UV treatment of drinking water is effective, but in order to work, the system must limit the flow rate of water through the system, based on the bulb's output or UV level, and the water must be pre-filtered to remove suspended solids that otherwise block UV light.

See details at UV ULTRAVIOLET LIGHT WATER TREATMENT

Also see UV vs GIARDIA LIMITATIONS found in this

article: UV WATER DISINFECTION, PORTABLE

Watch out: as we note in this article series, bacteria in well water, especially when it appears after heavy rain, most-often indicates that surface water is entering your water supply. If that's the case, ANY surface contaminant, pesticides, fertilizers, road salt, other contaminants that may be on nearby surfaces or in nearby ground-water may be entering your well.

Your local water test lab may have suggestions for just what additional contaminant tests should be performed.

RO (Reverse Osmosis) systems remove nearly all contaminants from water but also consume and waste water in the process; a typical RO system is installed as a "point of use" supply of clean drinking water, for example at a kitchen sink. A whole-house RO system is often impractical and costly and may not be necessary.

Details are at REVERSE OSMOSIS WATER TREATMENT

If tests confirm that the odors in your water are not from sulphur, then

see WATER SMELLS or ODORS, OTHER

...

Continue reading at FIX WATER WELL CONTAMINATION SOURCES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CHEATING ON WATER TESTS - buyer beware
• COLIFORM STANDARDS for DRINKING WATER - what are the allowable levels of total coliform and e-coli in drinking water?
• CONTAMINANT CLASSES, in WATER & links to home buyer advice about water testing, drinking
• FAILED WATER TESTS - WHAT TO DO - water testing procedural errors can foul up water test results
• FAILED WATER TESTS - WHEN to RE-TEST
• LANGLIER SATURATION INDEX LSI
• SIX STEPS to WELL WATER SAFETY
  • PROTECT GROUND WATER from CONTAMINANTS
  • 1. How To FIND WELL CONTAMINATION PROBLEMS
  • 2. WELL WATER TESTING STRATEGY
  • 3. INTERPRET WATER TEST RESULTS
  • 4. WELL CONSTRUCTION & MAINTENANCE
  • 5. CONSULT LOCAL WELL EXPERTS
  • 6. FIX WATER WELL CONTAMINATION SOURCES
• TOTAL COLIFORM TESTING for details about coliform bacteria test procedures and standards.
• WATER CONTAMINANT LEVELS & LIMITS for allowable water contaminant limits
• WATER ODOR DIAGNOSIS - SULPHUR
• WATER QUALITY TEST CHOICES & WATER TEST FEES
• WATER TESTING ADVICE - what water tests should you order, when, and how often?
• WATER TREATMENT EQUIPMENT CHOICES for treating contaminated water
• WELL CONSTRUCTION & MAINTENANCE for methods of building a safe water well
• WELL WATER CONTAMINATION: CAUSES, CURES - home

Suggested citation for this web page

WATER TEST INTERPRETATION 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 TESTING

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

Ask a Question or Search InspectApedia

Questions & answers or comments about how to understand the meaning of water potability test reports & what actions to take based on water test results.

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.

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

Citations & References

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

---

ADVERTISEMENT

---