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Here we discuss 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. 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.

© 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

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

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

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 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.

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WATER TEST INTERPRETATION
Common Water Tests for Bacteria
  PA - Coliform Bacteria Test
  M.F.T. - Coliform Bacteria Test
  MPN - Coliform Bacteria Test
  Interpreting Other Water Test Results
FAILED WATER TESTS - WHAT TO DO
  Water Test Procedure Errors
  Detecting Water Test Cheating
  Interpreting the Level of Bacteria
  WELL CHLORINATION SHOCKING PROCEDURE
FAILED WATER TESTS - WHEN to RE-TEST
  Wells that Pass a Second Water Test
  Wells that Fail a Second Water Test
  When to re-test a well
ODORS in WATER - TYPES, CAUSES
WATER TREATMENT EQUIPMENT CHOICES
  FILTERS for WATER
  FILTERS - SEDIMENT & IRON
  FILTERS - SULPHUR ODOR
  CHLORINATORS & CHARCOAL FILTERS
  REVERSE OSMOSIS WATER TREATMENT
  REVERSE OSMOSIS CONCENTRATE DISPOSAL
  UV -ULTRAVIOLET LIGHT TREATMENT
  WATER SOFTENERS
  WATER TREATMENT CHEMICAL SAFETY
EPA GUIDE to WATER QUALITY
FHA WATER TESTS REQUIRED
LEAD in WATER, ACTION GUIDE
  LEAD POISONING SYMPTOMS
  LEAD TEST VARIATION CAUSES
ODORS IN WATER
SEWAGE CONTAMINATION
WATER CONTAMINANT LEVELS
WATER TEST INTERPRETATION
WATER TESTING GUIDE
WATER TREATMENT GUIDE
WATER ODORS, CAUSE CURE
WATER PUMPS & WELLS
WATER QUALITY TESTS, CONTAMINANTS, TREATMENT
WATER QUANTITY IMPROVEMENT
WATER QUANTITY USAGE GUIDE
WATER SOFTENERS
WELL SHOCKING GUIDE
WELLS CISTERNS & SPRINGS
  WATER PRESSURE LOSS
  WELL CLEARANCE DISTANCES
  WELL LIFE EXPECTANCY
  WELL PIPING CHECK VALVES
  WELL PIPING FOOT VALVES
  WELL PUMP TYPES & LIFE EXPECTANCY
  WELL PUMP PRIMING PROCEDURE
WELL CHLORINATION SHOCKING PROCEDURE
  Chlorine in Wells - Safety Warnings
  Well Chlorination Procedure Details

More Information on Building Diagnostic Inspections and Repairs

• Cheating on water tests: Testing Water for Real Estate Transactions - make sure your water test is valid
• Drinking Water Testing Advice for home buyers home owners home inspectors
• Interpreting Drinking Water Test Results and Correcting Unsatisfactory Water
• Drinking Water Contaminant Levels - Maximum Allowed
• Drinking Water Contamination and Pollution How to Detect, Test, Correct, and Prevent Well Water Contamination - US EPA - Groundwater
• Lead Contamination in Drinking Water: Testing & Correction - Advice (This Article)
• Lead Testing & Correcting Contamination from Lead Water Supply Lines/Entry Mains - Lead Pipe Problems/Advice
• Extreme Lead Poisoning Symptoms Suggested by Feb. 2006 NY Times Article on Kosovo Roma Camps
• ATSDR: Nitrate/Nitrite Toxicity [Big, Slow-Loading File] U.S. Government ATSDR Science Corner - 2.5MB PDF
• Water testing for Pesticides: comprehensive and pesticides-example parameters
• Water Testing: background comments on classes of water contaminants, & links to home buyer advice about water testing, drinking water, water supply
• When and How to Shock or Chlorinate a Well - Procedure for Shocking a Well to (temporarily or maybe longer) "Correct" Bacterial Contamination
• Water Requirements, Home & Outdoor Living
• Typical Water Tests & Fees this water test fee schedule applies when testing is combined with other onsite building inspection services
• Drinking Water testing, contamination, correction - all topics
• General water testing and corrective measure advice: contact your local health department.

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