Wells and Well Water
Disinfection And Samples


The contractor is responsible for properly disinfecting any new well or well subjected to repairs or pump maintenance, upon completion of the work. Likewise, a pump installer must disinfect the well after the pump is installed, or repaired. Sufficient chlorine solution should be introduced into the well and water system to insure a minimum dosage of 100 mg/l. This chlorine solution should remain in the well and water system for a minimum of 24 hours. However, after 24 hours at least 25 mg/l of chlorine should still remain in the water. Under these conditions the well need not be disinfected again until the pump is set.

CAUTION: When working with chlorine, a person should be in a well-ventilated place. Chlorine powder or liquid should not come in contact with the skin or clothing. Chlorine solutions are best handled in wood, plastic or crockery containers because metal containers will corrode.

Every new, modified or reconditioned water source, including pumping equipment and the gravel used in gravel wall wells, should be similarly disinfected before the well is again placed into service. Such treatment should be performed when the well work is finished and again when the pump is installed or reinstalled.

a.      Use Table 6 to determine the amount of water in a drilled or driven well, based on casing size and the total depth of the well:

Table 6
Water in Gallonage of a Drilled or Driven Well

Diameter of Well Casing in inches

Gallons per foot


b.      For each 100 gallons of water in the well, calculated from Table 5 above, use 3 cups of liquid laundry bleach (5.25% chlorine) or 2 ounces of hypochlorite granules (70% chlorine). Mix the calculated amount of chlorine in about 10 gallons of water. For your convenience in measuring out the correct amount, the following conversion factors are listed:

2 cups = 1 pint
4 cups = 1 quart
16 ounces = 1 pound

c.      Pour this solution into the well making sure the casing walls are wetted before the seal or cap is installed.

d.      Connect one or more hoses to faucets on the discharge side of the pressure tank and run them into the top of the well casing. Start the pump, circulating the water back into the well for a least 15 minutes. Then open each faucet in the system until a chlorine smell or taste appears. Close all faucets. Seal the top of the well.

e.      Let stand for at least 12 hours, preferably 24 hours.

f.        After standing, run the pump to discharge water from each outlet until the chlorine odor and taste disappears.

Water Samples

After pumping the well and water system to remove the disinfectant, collect a water sample from the system using a sterile bottle provided by a laboratory that is certified to perform bacteriological analyses. Before the installation can be placed in service for human consumption, the water sample collected should have less than two coliform organisms per 100 milliliters of water. If the first sample is unsatisfactory, the disinfection procedure should be repeated and another sample collected for analysis. This procedure should continue until test results are satisfactory.

In addition to bacteriological testing, all new wells should be sampled for chemical analysis. The analysis should include all parameters listed in Table 7 below:

Table 7
Water Test Parameters and Drinking Water Standards

Test Parameter

State/Federal Drinking Water Standard

Aesthetic Recommendation

* Only one test needs to be performed for nitrates. However, a laboratory can report the results of its nitrate testing in either of the ways listed.

Total hardness, as CaCO3






Specific conductance, in mhos



Alkalinity (Total) as CaCO3




0.01 mg/l


Chlorides, as CI


250 mg/l

Dissolved solids


500 mg/l

Iron, as Fe (Total)


0.3 mg/l

Manganese, as Mn (Total)


0.05 mg/

Nitrates, expressed as Nitrogen *

10 mg/l


Nitrates, expressed as Nitrates *

45 mg/l




250 mg/l


4 mg/l

1 mg/l

If a resident has been advised by a physician to limit their dietary intake of sodium it is recommended that the water also be tested for sodium, so that source of sodium intake can be factored into the resident's total diet. If a water softener will be installed for treatment, then that source of sodium input to the water should also be factored into the resident's total diet. It also is desirable to test in the field for hydrogen sulfide.

It is the well owner's responsibility to obtain the required samples and have the laboratory tests made. Copies of the bacteriological and chemical analysis reports should be filed by with the Indiana Department of Natural Resources.

The well driller and/or water system installation contractor should construct and install the well and/or water system in accordance with these standards and acceptable industry practices. If these criteria are met, the well driller and water system installation contractor should not be responsible for the quality or quantity of water obtained.

5.3 Qualifications

In accordance with Indiana Code 25-39 and Rule 312 IAC 13, all water well drillers must be licensed by the Indiana Department of Natural Resources.

Well Abandonment

If a well is to be abandoned, it must be properly sealed to restore, as far as possible, the hydrologic conditions that existed before the well was drilled. An improperly abandoned well is an uncontrolled invasion point for contaminated water. Unsealed wells are a hazard to public health, safety, welfare, and to the preservation of our groundwater resource. Sealing of wells presents a number of problems, dependant on construction of the well, the geological formations it penetrates, and hydrologic conditions. A properly sealed water well will: (1) eliminate the physical hazard; (2) prevent groundwater contamination; 3) conserve the aquifer's yield; 4) maintain the aquifer's hydrostatic head; and (5) prevent intermingling of waters when more than one aquifer is involved. The Indiana Department of Natural Resources addresses proper well abandonment in its Rule 312 IAC 13-10.