Water drawn from a well was once precipitation that fell onto Earth's surface. It seeped into the ground and, over time, occupied the porous space in some subsurface material. Big particles that are in surface streams, such as leaf chunks, will not be seen in groundwater. So, yes, big particles are filtered out by the ground, along with some minerals and chemicals that are too small to see.
But groundwater can contain many different elements that are NOT filtered out by the ground and that we don't want in our drinking water. Some are naturally-occurring (like hydrogen sulfide) and some are human-made substances. Groundwater can contain petroleum, organic compounds, or other chemicals introduced by human activities.
Contaminated groundwater can occur if the well is located near land that is used for farming where certain kinds of chemicals are applied to crops, or near a gas station that has a leaking storage tank. Leakage from septic tanks and/or waste-disposal sites can also contaminate groundwater. A septic tank can introduce bacteria to the water. Pesticides and fertilizers that seep into farmed soil can eventually end up in water drawn from a well. Also, a well might have been placed in land that was once used for something like a garbage or chemical dump site. In any case, it is wise to have your well water tested for contaminants.
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Why is our porcelain sink stained brown?
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Why does my drinking water look cloudy sometimes?
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What can cause our water to have an earthy odor or to smell like rotten eggs?
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What can be causing our drinking water to have a reddish color?
Your water might be affected by iron, which is a commonly-occurring constituent of drinking water. Iron tends to add a rusty, reddish-brown (or sometimes yellow) color to water. If the color is more black than red, your water might contain a combination of iron and manganese. Both of these metals can cause staining of plumbing fixtures or laundry, but they are not known to cause health problems...
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- FAQ
How frequently are volatile organic compounds (VOCs) detected in groundwater?
Volatile organic compounds (VOCs), which are widely used in the manufacture of many products including refrigerants, plastics, adhesives, paints, and petroleum products, have been detected in about one-third of the wells sampled by the National Water-Quality Assessment (NAWQA) Program of the USGS. Chloroform and other trihalomethanes, the most commonly detected compounds, were found in about 9...
Where can I get my well water tested?
Some counties offer free well water testing, so check with your county first. If they don't, use this EPA website to find a list of state-certified laboratories in your area that do water testing, or contact your county or state health department or your State Certification Officer for assistance. Prices will vary depending on the laboratory and the test(s), but most people consider the cost to be...
Do you have information about water hardness in the United States?
See our map of water hardness (as calcium carbonate) in surface water of the United States. Hardness data (reflecting mostly calcium, plus a little magnesium) for individual drinking-water suppliers is at the EPA Office of Ground Water and Drinking Water website. It is important to note that the U.S. Environmental Protection Agency (EPA) has not set a legal limit or standard for hardness in water...
Why is our porcelain sink stained brown?
The brown stain is from a large amount of iron in your water. It is closely related to simple rust that you see on metal, which is iron oxide. Your water probably comes from groundwater that filtered through rocks containing iron-rich minerals on its way to the well. Learn more: Water Color USGS Drinking Water and Source Water Research
Why does my drinking water look cloudy sometimes?
Once in a while you get a glass of water that looks cloudy; maybe milky is a better term. After a few seconds it miraculously clears up! The cloudiness is due to tiny air bubbles in the water. Like any bubbles, the air rises to the top of the water and goes into the air, clearing up the water. The water in the pipes coming into your house might be under a bit of pressure. This causes gases (air)...
Where can I find information about my local drinking water supply?
The best way to learn about your local drinking water quality is to read the annual drinking water quality report/consumer confidence report that water suppliers now send out by July 1 of each year. The reports are often sent out with water bills, but they may be sent separately. The reports tell where drinking water comes from, what contaminants are in it, and at what levels. The U.S...
What can cause our water to have an earthy odor or to smell like rotten eggs?
Naturally-occurring organic compounds are created when plant material decays in lakes and reservoirs. Those organic compounds frequently cause musty, earthy odors, especially toward the end of summer. The odors can be objectionable, but generally are not harmful to health. However, odors can be caused by other constituents as well, so you might want to call your local Health Department and mention...
What can be causing our drinking water to have a reddish color?
Your water might be affected by iron, which is a commonly-occurring constituent of drinking water. Iron tends to add a rusty, reddish-brown (or sometimes yellow) color to water. If the color is more black than red, your water might contain a combination of iron and manganese. Both of these metals can cause staining of plumbing fixtures or laundry, but they are not known to cause health problems...
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