Groundwater
Bannock County Groundwater

Private Well Owners Toolbox


If your family gets drinking water from a private well, do you know if your water is safe to drink?

How can I protect my private water supply?

Protect your water supply by carefully managing activities near the water source. For households using a domestic well, this includes keeping contaminants away from sinkholes and the well itself. Keep hazardous chemicals out of septic systems.


Inspect your well and the area surrounding your well for possible pollution sources including:

  • Openings at the top of a well
  • Old, rusty or damaged well casings
  • Improper well casing installation
  • Faulty pump installation
  • Well located close to septic tanks, drain fields, cesspools, tile fields, sewer lines, kitchen sinks, drains, privies, barnyards, animal feedlots, abandoned wells, rock outcroppings, sinkholes, and quarries.

If you identify any suspected contamination sources, test your well water. Have any changes or repairs to your well made by qualified well drillers or pump installers. DEQ drinking water specialists, health district environmental health officers, or Idaho Rural Water Association circuit riders can assist you in making these observations and recommending improvements.


Is it safe? Test Your Well Water Regularly

It is your responsibility to test your private well water. Local and state agencies typically do NOT test private well water; they only test public water systems.

Some areas of North Bannock County have been identified as Nitrate Priority Areas. Many of the wells in these areas have nitrate levels close to – or above- the safe drinking water limit.  Be sure to find out if you live in a Nitrate Priority Area. http://www.deq.idaho.gov/media/473071-nitrate_ground_water_fs_0710.pdf

Test your water at least annually. Many people claim their water tastes great and that they’ve never gotten sick from it. The truth of the matter is you can’t tell if your water is safe by the taste, smell, or color of the water. The only way to know is to test it. Locally, the most likely contaminants are bacteria and nitrate.

Type of Contaminant When to Test Treatment Level
Bacteria Once a year Treat any amount
Nitrate Once a year 10 mg/L or higher

mg/L = milligrams per liter of water


Well Construction Issues

How can my private well become contaminated?

Bacteria, chemicals, or biological waste may contaminate your well in one or more of the following ways:

  1. The well may not have a vermin-proof cap, allowing insects that carry bacteria to enter the well.
  2. There is a source of contamination, such as a septic system, too close to the well or the well casing and surface seal are not deep enough to assure that recharge water receives sufficient filtration to remove bacteria.
  3. The well may be constructed using poor sanitary practices. New wells often show contamination because:
    • The drillhole was contaminated by dirty tools, pipe or drilling water.
    • New piping, pump or pressure system components were not disinfected prior to use, assembly or installationNote: The state well code requires disinfection of new wells, pumping equipment, and water systems prior to use.
  4. Contaminated surface water or groundwater can enter an improperly constructed well in the following ways:
    • Hand dug wells lined with boards, brick, stone or tile sections permit unfiltered surface water and near-surface waters to seep into the well through cracks in the lining.
    • Improperly sealed casing may permit surface water or contaminated groundwater to move vertically downward along the space between the borehole wall and the casing, contaminating clean aquifers.
    • The well casing does not extend far enough above the ground allowing surface water to enter the well or because a hand pump base does not have a watertight seal where it attaches to the casing.
    • The well casing ends in a poorly designed well pit that is likely to flood or collect seepage of contaminated groundwater.
    • Old well casings may rust through, leaving holes near the ground surface where surface water or near-surface waters can seep in and contaminate deeper groundwater.
    • The aquifer supplying the well is composed of fractured rock, which has poor water-filtering properties
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