Flooding - Water Quality & Health Considerations

If your household is served by a private well and that well is reached by the floodwaters, it will need to be tested and disinfected after the waters recede. Below, you'll find basic details about treating wells. However, specific questions and concerns about testing the quality of your well water should be directed to the Hunterdon County Department of Health.

Basic Health Guidelines to Follow After a Flood

Water for Drinking, Cooking, and Personal Hygiene Safe water for drinking, cooking, and personal hygiene includes boiled, bottled, or treated water. Remember:

  • Do not use contaminated water to wash your hands, wash dishes, brush your teeth, wash and prepare food, make ice, or make baby formula. If possible, use baby formula that does not need to have water added. And if you have it, use an alcohol-based hand sanitizer to wash your hands.
  • If you use bottled water, be sure it came from a safe source. If you do not know that the water came from a safe source, you should boil or treat it before you use it. Use only bottled, boiled, or treated water until your supply is tested and found safe.
  • Boiling water, when practical, is the preferred way to kill harmful bacteria and parasites. Bringing water to a rolling boil for 1 minute will kill most organisms.
  • When boiling water is not practical, you can treat water with chlorine tablets, iodine tablets, or unscented household chlorine bleach (5.25% sodium hypochlorite):
    • If you use chlorine tablets or iodine tablets, follow the directions that come with the tablets.
    • If you use household chlorine bleach, add 1/8 teaspoon (~0.75 mL) of bleach per gallon of water if the water is clear. For cloudy water, add 1/4 teaspoon (~1.50 mL) of bleach per gallon. Mix the solution thoroughly and let it stand for about 30 minutes before using it.

Note: Treating water with chlorine tablets, iodine tablets, or liquid bleach will not kill parasitic organisms. Only boiling can do this.

Use a bleach solution to rinse water containers before reusing them. Use water storage tanks and other types of containers with caution. For example, fire truck storage tanks and previously used cans or bottles may be contaminated with microbes or chemicals. Do not rely on untested devices for decontaminating water.

Disinfecting Wells

If you suspect that your well may be contaminated, contact the Hunterdon County Department of Health for specific advice. Here are the department's recommended procedures for disinfecting wells.

To Disinfect Potable Wells

Disinfection is accomplished most effectively with a chlorine-containing chemical. Any common household liquid bleach that contains approximately five (5) percent "active" ingredients — usually sodium hypochlorite — is the most convenient chemical to use.

The following table shows the proper amount of liquid bleach to be added directly to the well. All taps should be opened until chlorine odor is detected, and then held overnight or at least for several hours. The entire system should then be flushed out prior to reuse.

Important: All electrical power to the well pump should be shut off prior to removing well cap.

Required: Volume of five (5) percent bleach solution.

(Disinfection strength approximately 50 parts per million)

Diameter of Well

Depth of Well

20 feet30 feet40 feet50 feet100 feet200 feet
Up to 6"4 ounce 6 ounce 80 ounce 10 ounce 20 ounce 4 quart
6" to 12"16 ounce  24 ounce  32 ounce  2 ounce  3 ounce  4 ounce  
12" to 24"
2 quart3 quart4 quart---
24" to 48"2 gallon3 gallon4 gallon---

The table above represents bleach volume in liquid ounces (oz).

Note: 32 ounces (oz) = 1 quart (qt). A standard measuring cup = 8 ounces (oz).

Additional Information