Photograph of  this antiquated laundry sink with several unsanitary plumbing violations in view.Well Water Test Failure: Now What
When to Re-Test or Not Re-Test a Drinking Water Well

  • FAILED WATER TESTS - WHEN to RE-TEST - CONTENTS: When a well fails a water test, under what conditions do we just re-test? When is re-testing a drinking water well useful and when is it a waste of time and money? What to do various high or low bacterial levels mean when a well fails a potability test?
  • POST a QUESTION or READ FAQs about how, when, & why you should test (or wait to re-test) a failed water well after a bacteria or potability test

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

Acting on Unsatisfactory or Contaminated Water Test Results - Advice for Home Buyers & Home Owners.

This article explains when it is useful to re-test a drinking water well after it has failed a bacteria test. We explain how to interpret and thus act on the results of 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.

Green links show where you are. © Copyright 2015, All Rights Reserved.

Handling Failed Wells that Pass a Second Water Test: What to do if water passes after disinfection

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.

Article Contents

When will shocking the well actually cure a problem?

  • If the well water contamination level was a relatively low bacteria count and was caused by an unsanitary growth in plumbing equipment this treatment can "correct" the problem.
  • If the contamination was a relatively low to modest count and is caused by a persistent source of contamination, this treatment can appear to correct the problem by killing off bacteria. But the problem can recur.

When does well disinfection not work?

  • If the contamination is from a major source, with a high bacteria count, repeated sterilization and testing of the well may yield inconsistent results, sometimes passing, sometimes not.

What's wrong with just re-shocking the well and relying on the next OK water test result?

  • "Shocking" a well can temporarily make unacceptable water look fine. If no other corrective measures were taken than to "shock" the well, it is appropriate to follow the first acceptable water test with a second and perhaps even a third, spaced a week or more apart.

What's the best course of action for a buyer of a home that fails a well water test?

  • If in a real estate sale transaction the schedule does not permit these tests before closing, a buyer should consider requiring an escrow fund set aside during purchase of the property. This fund will guarantee acceptable water while giving the buyer a reasonable time, perhaps a month, to perform additional testing..

When to re-test a well that has been shocked with chlorine bleach or some other disinfectant

To be maximally effective at attempting to disinfect a well, the chlorine solution needs to be in contact with the entire well casing and piping and water storage tank for 24 hours. Then the bleach-treated water is flushed from every fixture until there is no more bleach odor. A realtor/seller anxious to "pass" a bacteria test will try for an immediate re-test at that point.

WARNING: Wait. Don't re-test a well too soon.

We suggest a minimum of five days, preferably seven to ten days before re-testing a shocked well. If there is a persistent source of bacterial contamination shocking the well won't fix anything.

The longer you wait before re-testing a well for potability, the more time you're giving for the bacteria to reappear at a level sufficient to be picked up in the next water test.

If circumstances force a too-quick follow-up bacteria test real to meet a estate closing date before adequate wait time has been allowed for re-testing to be more credible, we recommend that the parties agree to escrow the cost of a proper water treatment system ($5000. to $10,000) and to allow the new buyer 30 days to conduct follow-up testing. If at the end of that period the well is ok the escrow can be released.

Handling Failed Wells that Fail a Second Water Test Again: What to do if water fails a follow-up water test after well disinfection by Chlorination or Well Shocking

  • If the well water test still is not satisfactory, it is likely that there is a persistent source of contamination. Common sources of contamination include loose or damaged cap on buried well casings, loose or damaged pitless adapter (where buried water line enters the well casing), a bad plumbing connection in piping between the well and the building, spiders living in the well head and possibly insects they've dropped into the well, a dead animal in a well which was not properly capped, and, less common, a cracked or damaged well casing.

    Damaged well casings can involve significant expense to repair or replace.
  • Since water systems can change, drinking water from private wells should be analyzed on a regular basis. The frequency of testing should be determined by the history of the water quality of the well.
  • Usually the property owner/seller is responsible for correcting unacceptable water. Check with your attorney and your contract regarding this matter.
  • Often sellers have the well "shocked" using the sterilization treatment described above as a quick "fix" for a well that fails a bacteria test. This is a reasonable step to try IF the well has not already been shocked but otherwise, just trying this step over and over is probably wasting time and money, and it risks covering up a persistent contamination source that needs to be addressed.
  • In addition to sterilizing the well, an owner/seller or the new owner of a well that has failed a water test more than once in succession should:
    • Find the contamination source: have an experienced plumber or well service company look for, find, and correct a source of contamination such as a bad plumbing connection at the well (pitless adapter or well casing cap), bad plumbing between well and house (broken or leaky pipe joint), or bad or soiled plumbing components inside the house.
    • install water treatment/sterilization equipment such as a chlorinator/charcoal filter system or an ultra-violet light system. These systems work but require maintenance. Water treatment equipment are discussed in the next section.
  • Correcting the source of contamination is naturally preferred. But if a home is being sold, often schedule pressures do not permit longer investigation by a plumber to find a problem if it is not obvious. Therefore to provide safe potable (drinkable) water immediately, a water purification treatment system may be installed. If that course of action is followed, we still recommend that the new owner/occupants attempt to find and correct the source rather than having to maintain equipment.
  • See WATER TREATMENT EQUIPMENT CHOICES for details of how we correct contaminated drinking water when simple well disinfection doesn't do the trick.


Continue reading at WELL CHLORINATION SHOCKING PROCEDURE or select a topic from the More Reading links shown below.



Suggested citation for this web page

FAILED WATER TESTS - WHEN to RE-TEST at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

More Reading

Green link shows where you are in this article series.


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Questions & answers or comments about how, when, & why you should test (or wait to re-test) a failed water well after a bacteria or potability test.

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, 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

HTML Comment Box is loading comments...

Technical Reviewers & References

Publisher's Google+ Page by Daniel Friedman

Click to Show or Hide Citations & References