How can I disinfect my water system?

Please read all 8 steps before beginning disinfection

You will need the following equipment:

Several gallons of household laundry bleach, avoid scented products
A plastic mixing container - we recommend a new 25-gallon garbage can
Garden hose attached to the system to be disinfected

Step 1: How much chlorine?

In order to remedy a well contaminated with bacteria, disinfection is required. Chlorine is the most common disinfectant. How much chlorine solution you will need depends on the size and depth of your well. The following chart will help

Casing Diameter Minimum amount of chlorine solution to displace the volume of water in the well

2" Prepare 2 gallons chlorine solution for every 10 feet of well depth

4" Prepare 7 gallons chlorine solution for every 10 feet of well depth

6" Prepare 15 gallons chlorine solution for every 10 feet of well depth

8" Prepare 26 gallons chlorine solution for every 10 feet of well depth

Casing Diameter	Minimum amount of chlorine solution to displace the volume of water in the well
2"	Prepare 2 gallons chlorine solution for every 10 feet of well depth
4"	Prepare 7 gallons chlorine solution for every 10 feet of well depth
6"	Prepare 15 gallons chlorine solution for every 10 feet of well depth
8"	Prepare 26 gallons chlorine solution for every 10 feet of well depth

Step 2: Prepare the chlorine solution

You will need a sanitary container to mix the water and chlorine. Mixing can be done 25 gallons at a time in a new plastic garbage can. Note: Never use (even new) garbage cans to store drinking water.

To prepare the chlorine solution, mix 1 part of the household laundry bleach with 100 parts of water. For example: mix 1 gallon bleach with 100 gallons water. Prepare enough solution to meet or exceed the total volume of the well.

Step 3: Put the solution down the well

Before proceeding, make sure the power is disconnected from the well. Then, carefully remove the cap from the well and pout the entire bleach and water mixture into the well. Take caution not to spill any of the chlorine mixture outside the casing

Step 4: Rinse down the casing

You want to circulate the chlorine solution throughout the water system to insure total disinfection. To do this, rinse down the sides of the well casing with a garden hose for 5-10 minutes. Make sure the garden hose is connected to the system being chlorinated!

Step 5: Disinfect your plumbing system

Turn off the heating element in you water heater to save energy during this next step. After the heating element is off, go to each water tap connected to your plumbing system and run the water until you begin to detect a bleach smell. At that point turn the water off and go to the next tap.

Step 6: Wait

Disinfection is not a quick process! Let the chlorine solution remain in the system for at least 24 hours.

Step 7: Remove the chlorine

Remember, chlorine can kill grass and fish so be sure not to dump the spent chlorine solution where it will cause harm. Also, do not dump the solution into your private septic system and check with your municipality before dumping into any public sewer system.

Attach a garden hose to your system and run the water to an area where the chlorine will do no damage. Pump until you can no longer detect the chlorine smell. If necessary follow this procedure for you plumbing system by running each of the cold water taps.

Step 8: Resample

Wait until all traces of chlorine have been flushed from the system, usually 24 hours; then, resample the well.

Produced By: Wisconsin DNR, Bureau of Drinking Water and Groundwater
Copyright: 1996, Wisconsin DNR