Photograph of  a loose, unsanitary well plumbing system exposed to surface water runoffr  © DJ FriedmanSources of Well Water Contamination

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What are the main sources of well water contamination.

Where do well water contaminants come from & how do they get into the well. Knowing the answers can help prevent or cure contaminated well water.

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Where Do Ground Water Pollutants & Thus Well Contaminants Come From?

Unidentified chemical drums discovered during a home inspection might indicate an environmental site contamination hazard.Here the EPA (with some added commentary) describes common sources of well contamination. We have added links to more detailed diagnostic articles about individual well water contamination problems.

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Sources for more information and help are also listed. [Editing for clarity by DF are marked by brackets or italics] Initial Source: EPA 816-K-02-003 January 2002. Also see How To Spot Well Contamination Problems later in this article series.

Understanding and spotting possible pollution sources is important. It's the first step to safeguard drinking water for you and your family.

Some threats come from nature. Naturally occurring contaminants such as minerals can present a health risk. Other potential sources come from past or present human activity - things that we do, make, and use such as mining, farming and using chemicals. Some of these activities may result in the pollution of the water we drink.

Several sources of pollution are easy to spot by sight, taste, or smell. (See Quick Reference List.), however many serious problems can only be found by testing your water. Knowing the possible threats in your area will help you decide on the kind of tests you need.

Visual Evidence of Water Contamination Problems

Sources of Visible Water Contaminatiom-like scale, stains, or floating dirt/debris

  • Scale or scum from calcium or magnesium salts in water. At WATER SOFTENERS & CONDITIONERS we discuss formation of scale in water softeners; at CLOGGED SUPPLY PIPING we discuss clogged water piping due to scale formation.
  • Unclear/turbid water from dirt, clay salts, silt or rust in water
  • Green stains on sinks or faucets caused by high acidity
  • Brown-red stains on sinks, dishwasher, or clothes in wash points to dissolved iron in water
  • Cloudy water that clears upon standing may have air bubbles from poorly working pump or problem with filters.

Sources of Water Tastes as Evidence of Water Contamination

  • Salty or brackish taste from high sodium content in water
  • Alkali/soapy taste from dissolved alkaline minerals in water
  • Metallic taste from acidity or high iron content in water
  • Chemical taste from industrial chemicals or pesticides

Sources of Water Smells that may Indicate Water Contamination

For detailed advice on diagnosing and curing water odors see WATER ODORS, CAUSE CURE.

Sources of Sulphur or Rotten Egg Smells in Water

  • A rotten egg odor or sulphur odor in water can be from dissolved hydrogen sulfide gas or certain bacteria in your water.
  • A rotten egg or "sulphur odor" in drinking water may also come from the water heater and may be easy to fix. If the smell only comes with hot water it is likely from a part in your hot water heater. [The water heater's sacrificial anode, a rod sticking down into the water heater tank, is intended to reduce water tank corrosion and thus extend water tank life. But when the anode is badly corroded or dissolved itself, this condition can be a source of smelly water.

    Check for this condition before doing something more expensive to address water odors. We most often notice this odor when the home has been unoccupied for some time and the water heater has become deteriorated. Key is that the odor is only noticed when running the hot water--DF]
  • We discuss the hot water tank sacrificial anode and dip tube in more detail
    at Check the Sacrificial Anode & Dip Tube of Your Water Heater Tank. [DF addition/edit]
  • A sulfurous smell or rotten egg smell may also be due to the combination of loss of oxygen in water (hypoxia), or low oxygen levels, combined with algae which feeds and then dies in rivers, lakes, ponds, streams, or even large areas such as the Gulf of Mexico where agricultural runoff in the Mississippi river results in high nitrogen levels in water entering the Gulf.

    In 2008 the "dead zone" in the Gulf of Mexico was reported by the New York Times as likely to form a smelly sulphur-smelling zone of roe than 8,500 square miles.
  • We provide a detailed list of sewer and sulphur gas odor sources at Sources of Sulphur Odors in Buildings.

Sources of Other Odors in Water

  • A detergent odor in water and water that foams when drawn could be seepage [into the well] from septic tanks [or other groundwater] into your water well.
  • A gasoline or oil smell in water indicates fuel oil or gasoline likely seeping from a tank into the water supply. [We found a property at which an owner was using an old "abandoned" drilled well casing to dispose of his used motor oil. This is an example of why it's a good idea to properly seal abandoned wells, making it unlikely that an un-used well will become a pipe for contaminants to be sent directly into the local aquifer--DF]
  • Methane gas or musty/earthy smell in water may be from decaying organic matter in water. [We've had reports, especially from mining areas such as portions of Pennsylvania in the U.S. in which underground methane was seeping into the well through rock fissures. One client could on occasion light gas coming from their kitchen faucet! Be careful, such conditions are dangerous and risk explosion or fire--DF] See METHANE GAS SOURCES for details about sources of methane gas in and around buildings and in the water supply or in wells.
  • Chlorine smell in water may be from excessive chlorination [or from improper or inadequate water treatment systems that have stopped filtering excessive chlorine in the post-processing step after using a chlorinator to kill bacteria in a water supply. -DF.]

For detailed advice on diagnosing and curing water odors see WATER ODORS, CAUSE CURE.

Watch Out: Many serious problems (bacteria, heavy metals, nitrates, radon, and many chemicals) can only be found by laboratory testing of water.

  • WATER WELL PROTECTION & RESTORATION explains the importance of protecting a well from polluted groundwater, of protecting groundwater from accidental pollutaion through open wells, and also how to return a well to operation and use after area flooding.
  • WELL FLOOD DAMAGE REPAIR describes how flood waters can cause well and water system piping contamination and what to do about it before using well water after area flooding.



Continue reading at WATER POLLUTION - NATURAL SOURCES or select a topic from the More Reading links shown below.


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WATER POLLUTANT SOURCES at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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