Private Water Supply Wells
Approximately 67 percent of the residents of Iowa depend on groundwater for their daily water needs. The groundwater is accessed through the use of municipal or public water supply wells, or private water supply wells. There are approximately 206,000 rural Iowans who depend primarily on private wells to meet their daily water needs.
Safe drinking water is a result of understanding how a well interacts with your local land use patterns, geology, and well construction techniques. Things like proper well location, high quality construction materials, and protective installation techniques done by professional well contractors are essential to providing a safe supply of drinking water for your family.
This web page will provide you with some basic information about water supply wells and groundwater. This information can be used to help you make informed decisions about the water that you use.
In Iowa, water supply wells fall into two categories: private water supply wells and public water supply wells.
A water supply well meets the definition of "private water supply" when the well serves fewer than 15 individual connections or regularly serves and average of less than 25 individuals for less than 60 days out of the year. A private well is not under the control of a supplier of water but rather the well user(s) control the water supply, treatment, maintenance, and repair of the complete water system. Private water supplies wells are permitted through the local county health offices who issue both a local and a state well construction permit.
A water supply well meets the definition of a "public water supply" when the well and distribution system has at least 15 service connections or regularly serves an average of at least 25 individuals daily at least 60 days out of the year. The term includes (1) any collection, treatment, storage, and distribution facilities under control of the supplier of water and used primarily in connection with the system; and (2) any collection (including wells) or pretreatment storage facilities not under the control of the supplier which are used primarily in connection with the system. Public water supply wells and systems are permitted through Iowa DNR Water Supply Engineering.
Well Basics
Water supply wells generally fall into four categories -
1. Drilled or Cased Wells - Drilled wells for home, farm and light commercial use generally are 8" or less in diameter and draw their water from alluvial basins, inter-till sand and gravel deposits, or deeper bedrock that can hold and transmit water, like porous or fractured limestone and sandstone. Drilled wells are normally designed to obtain water from aquifers in geological settings that offer additional protection from surface water and shallow groundwater. In Iowa, it is common to find well depths from 40' - 2000' in depth depending on the quantity of water needed and the quality of water desired. In comparison, when we look at wells installed for large water users like industry and water suppliers, the well casing size can be as large as 30" in diameter and the well depth exceed 2000'. Drilled wells make up the majority of the new well installations in Iowa and when placed, constructed and maintained properly, drilled wells are the most dependable and safe source of drinking water.
2. Bored or Augered Wells - Bored wells are mainly found in areas that have too little aquifer thickness to support normal household needs through the use of a drilled well. This type of well is commonly called a "cistern well" because of the large diameter. It is common to find bored wells up to 48" in diameter. This large diameter allows the well to hold a large volume of water when installed below the water table. The larger quantity of water can help sustain the peak water needs of the well user. In Iowa, most bored wells are found in the areas of central, south central, and western where the ancient glaciers once rested. It is common to find that bored wells can not keep up with the water production needed for users who need more than just a household supply well. Bored wells installed prior to 1982 usually have fewer protective construction features which results in greater water quality issues when compared to those wells installed after 1982. Newer bored wells when placed, constructed and maintained properly can be a dependable and safe source of drinking water.
3. Driven or Sandpoint Wells - This type of well is usually found in alluvial river basins and adjoining low laying areas nearby rivers, streams and waterways. These wells are generally less than 2" in diameter and are often less than 30' in depth. A sandpoint well is installed by joining a screened drive point (or sandpoint) with lengths of pipe and driving the assembly into a shallow sand and gravel aquifer. Although a sandpoint well can provide safe drinking water if properly placed and maintained, the department does not recommend using a sandpoint well as a potable drinking water source due to the uncertainty of the shallow groundwater sources.
4. Hand Dug Wells - This type of well is not permitted for new construction any more but can be found located on properties that are underlain by glacial till with homes that were originally built before 1940. Hand dug wells are generally 48" in diameter and larger. Some of the largest hand dug wells in the state have been documented as large as 36' in diameter. As the name implies, these wells were constructed using hand labor (along with machine labor for extremely large diameters) to excavate a borehole. The borehole could be lined with brick, field stone, or even wood. Hand dug wells exhibit poor water quality due to the combination of utilizing the most shallow groundwater and being constructed of materials that do not block out surface water or shallow groundwater. The Iowa DNR does not recommend that you use a hand dug well as a source for drinking water.
Standards Required for Well Installation
To ensure that you have the best opportunity to use a safe and dependable groundwater resource, the Iowa DNR sets minimum standards for both the well construction and the contractor you hire to install your water supply. The private well construction standards are a statewide "minimum" standard. Some geological conditions and/or aquifers may need greater than minimum standards used during well construction to ensure that your well can supply the highest quality drinking water possible for your location. Please consult with an Iowa DNR Certified Well Contractor to learn more about what role well construction has in protecting your resource. Below are five areas that are covered by statewide private well rules.
Certified Well Contractors - The installation of all water supply wells in Iowa requires that the homeowner hire an individual Iowa DNR Certified Well Driller to perform the well construction or perform the actual work themselves. All well construction must meet the minimum construction standards for the area of installation. The Iowa DNR does not recommend that you undertake any well services yourself but You should only hire a well driller who is currently certified with Iowa DNR Well Contractor Certification in the proper well services disciplines.
Construction Standards - Statewide well construction standards offer minimum levels of well protection but some areas of the state may require greater protections be used in the construction of the well. Increasing the amount and depth of casing to avoid poor quality groundwater and/or grouting the well to a deeper level will help ensure long term protection to the water supply well and aquifer are specific to the region the well is located.
Water Testing- We require that all water supplies wells be tested to determine if the water is safe to drink when the well is newly constructed or when the well is serviced or repaired. It is the well owner's responsibility to insure that the testing is completed and that the water users know the outcome of the testing - safe to drink or unsafe to drink.
Well Repair and Maintenance - All well service work and repair must meet Chapter 49 standards including well disinfection and water testing.
Well Plugging- When a well is no longer needed or is in a state of repair that eliminates the possibility of repairing the well for use, the well must be abandoned and properly plugged.
Special Considerations for Drinking Water Wells Located in Karst Bedrock Conditions
The term
"Karst" refers to terrain characterized by the presence of easily dissolved bedrock (limestone and dolomite) near the ground surface. Because carbonate rocks can be dissolved by groundwater, karst areas are often characterized by sinkholes, springs, and losing streams - a stream where some or all of the surface flow enters the groundwater through a bedrock surface feature that connects the stream to openings in the bedrock below the stream.
The picture to the left shows a segment of a loosing stream where the stream water enters bedrock and becomes groundwater.
Karst features diagram
The shallow groundwater located in or near Karst areas can be highly vulnerable to contamination because contaminants can travel quickly from surface water to the local shallow aquifers through losing streams, sinkholes, and bedrock fractures and cave systems. This bypasses the natural tendency for water to be filtered by the soils which provide natural water treatment processes.
Because of its potential surface influence and the prevalence of agriculture and livestock in Karst regions of our state, localized contamination of karst aquifers with nutrients, pesticides, and bacteria can be a concern. Contaminated aquifers should not be used for drinking water purposes unless proper water treatment is used and maintained.
Although Karst features can be found in a number of locations across Iowa, they are most abundant in the NE corner our state.
The Karst maps to found on either side of this text are available to help you determine if your property is located on or nearby Karst bedrock features. For additional information - please contact
the Iowa Geological and Water Survey.
When you live in a Karst area and use a water supply well for your drinking water needs, it is important to understand how protected your water source is based on your specific location, the land use practices in your area, your well's construction, and most importantly of all - frequent sampling and analysis of your well water . With this additional information you will be able to understand the quality of your drinking water and any health risks that can be attributed to the shallow groundwater.
Most modern water supply wells include protective construction features designed to exclude the shallow groundwater associated with Karst terrain. These features include setting the well casing to a greater depth to exclude the upper groundwater; full depth grouting/sealing of the well casing to help reduce/eliminate the chance that shallow groundwater will move downward along the well casing and into the well; and utilizing groundwater from only known deeper, protected and safe aquifers. If you live in a Karst area and are considering a new well, make sure that you hire only Iowa DNR Certified Well Drillers and ask them to document what construction features they will use to help protect your well and drinking water quality.
Older water supply wells - especially those constructed before 1982 - may or may not have adequate protections in place to ensure that your well obtains its water from deeper, protected aquifers. If you have an older water supply well or if you do not know the depth and construction details of your water supply well, you should have your well water sampled at least on a yearly basis so that you know the water is safe to drink. You should also consider hiring an Iowa DNR Certified Well Contractor to perform a full well inspection to try and determine if your well includes construction features that will help ensure the well only accesses water from a known safe aquifers and that your well provides safe drinking water.
If you live in an area of Karst terrain and your well obtains its water from shallow groundwater sources that have been proven to be unsafe to drink and renovating or replacing your well is not an option, you should use a known safe alternative source for your drinking water needs or consider the use of a "reverse osmosis" water treatment system at each point of use where you want to obtain your drinking water. Reverse Osmosis systems when properly designed, installed and maintained, can provide you with a safe source of drinking water under Karst conditions.
To learn more about water testing for your private well, please contact your
local county environmental health specialist the State Hygienic Laboratory, or
the Iowa DNR Private Well Program.
Natural Arsenic in Drinking Water Supplies
Arsenic is a naturally occurring element that can be found in many locations in our state. It usually occurs in conjunction with certain sulfide minerals that are deposited as part of our soil and bedrock formations. The environment that created the arsenic deposits is a result of millions of years of accumulation, sedimentation and erosion.
Traces of arsenic can be found in water sources including groundwater, lakes, rivers and oceans. Foods like fruits, vegetables and seafood can also contain trace amounts of arsenic. Since arsenic is a natural part of our environment, everyone is exposed to small amounts of this element during their lifetime.
Arsenic can be found in groundwater sources that supply water supply wells. Because of this, it is important for all well users to understand if their water supply contains any arsenic. Neither state nor federal governments have set minimum drinking water quality standards for private wells and there are no requirements for mandatory testing except for coliform bacteria and nitrates - at any time a well is newly constructed or repaired. This means that it is the responsibility of the well owner and the water users to perform testing on their own private sources so that they understand the quality of their drinking water and any adverse health effects the water may pose.
A recent study by the University of Iowa tested 475 private wells for various contaminants. Out of this group, eight percent (8%) of the wells were found to have arsenic levels above the health threshold. The map to the right provides a basic view of the test results. The red dots indicate arsenic levels above the maximum recommended levels and the blue dots indicate arsenic levels below the maximum recommended levels.
Because of the potential health risks that arsenic poses, public health and environmental health officials encourage all private well owners to have their wells tested for arsenic at least one time. This testing will provide the well owner and water user(s) with important information on any health risks that arsenic may pose. In general, the cost for arsenic testing is approximately $20 per sample. Additional information on arsenic testing can be obtained by viewing the State Hygienic Laboratory arsenic web page.
If a private well user discovers that arsenic is present in their water supply and the levels pose a health risk, there are water treatment options that help reduce or eliminate the risk from arsenic. Treatment systems designed to reduce or remove arsenic include reverse osmosis water treatment systems, water distillers, or one or more water filter beds that contain activated alumina. Because it is not necessary to treat all of the water in a home, the household drinking water needs can be met by installing a “point of use” treatment system at a convenient location like the kitchen sink, or the water tap on the refrigerator and ice maker.
Information about arsenic treatment options is available in an informational brochure from the State Hygienic Laboratory at the University of Iowa. The booklet is titled "Well Water Quality and Home Treatment Systems." Additional information on home water treatment devices can be obtained from a Water Systems Council information page titled "Drinking Water Treatments."
All water treatment systems advertised for sale or sold in Iowa must be registered with the Iowa Department of Public Health (IDPH). Please visit the following IDPH website for more information. It is recommended that a licensed plumber install the system and that the water user understand the periodic maintenance and testing that the system requires. It is important to consult with a water treatment system sales professional to determine what types (species) of arsenic is present in the well water so that the correct system for arsenic removal is purchased. For more information or questions regarding home treatment systems, contact Randy Lane at IDPH, 515-281-5894, randy.lane@idph.iowa.gov.
When choosing a water treatment system to reduce or remove arsenic, it is important to consult with a water treatment system sales professional to determine what types (species) of arsenic are present in the well water. In some cases, arsenic removal is a multi-step process and requires additional treatment equipment. This step will help ensure that the water treatment system placed on your water system will perform properly and provide you with safe drinking water. Once you have chosen the treatment system, we recommended that a licensed plumber install the system and that the water user be trained on system operation, periodic system maintenance and water testing to confirm that the system provides adequate water treatment. For more information or questions regarding home treatment systems, contact Randy Lane at IDPH, 515-281-5894.
Additional information on specific water treatment products is available from the National Sanitation Foundation.
People can experience adverse health impacts if they are exposed to arsenic levels over a period of years that are significantly above the federal public drinking water standard. Individuals who feel they may be experiencing health problems related to arsenic exposure can contact the Iowa Department of Public Health
for additional information.
The Iowa DNR informational document "Arsenic in Iowa's Drinking Water."
Environmental Protection Agency Arsenic information
Read our "Private Well Testing" web page for additional water testing information.
General Drinking Water Resources
The following web resources for additional information are provided for your convenience.
- US Environmental Protection Agency's publication "Drinking Water From Household Wells."
- The Water Systems Council, a nonprofit organization solely focused on individual wells and other well-based systems, recently opened a hotline for well owners partially funded by a grant from the U.S. EPA.
- Well owners with questions about wells and well water can call the new hotline at 1-888-395-1033 or visit their website at www.wellcarehotline.org.
- Iowa Farm*A*Syst/Home*A*Syst, provides fact sheets and worksheets to help farmers and rural residents assess pollution risks and develop management plans geared toward their circumstances. For example, Farm*A*Syst helps farmers and ranchers identify pollution risks from nitrates, microbes, and toxic chemicals. Home*A*Syst reaches homeowners who face pollution risks from faulty septic systems, pesticide use, petroleum leaks, and hazardous waste disposal. Click here for their website
- American Ground Water Trust, a non-profit education organization providing information to the well owner. Click here for their website
- National Ground Water Association's Wellowner.org, providing information to consumers on ground water and water wells through wellowner.org. Click here for their website
- American Water Works Association, an international nonprofit scientific and educational society dedicated to the improvement of drinking water quality and supply. Click here for their website
- Centers for Disease Control and Prevention has information on private drinking water wells and your health. Click here for their website
- Ground Water Foundation, a nonprofit organization dedicated to educating and motivating people to care for and about ground water. Click here for their website
- National Drinking Water Clearinghouse, a public service organization that collects, develops, and distributed timely drinking water-related information. Sponsored through the US Department of Agriculture's Rural Utilities Service. Click here for their website
Well Contractor Trade Organizations
- The National Groundwater Association is a national organization representing well contractors and groundwater scientists. Click here for their website
- The Iowa Water Well Association is a statewide organization representing well contractors and the well industry in Iowa. Click here for their website
- For more information contact -
Russell Tell, Environmental Specialist Senior
401 SW 7th St, Suite M
Des Moines, IA 50309-4611
(515) 725-0462 or by Fax: (515) 725-0348
russell.tell@dnr.iowa.gov