Shock Chlorination: How to Get Rid of Bacteria in Your Well Water
So, you just found out that bacteria live in your well water…
Never fear. This guide give you a clear method for treating your drinking water to remove coliform, E. coli, and other potentially harmful bacteria living in your well water and pipes.
The method we suggest and describe below is broadly called “Shock Chlorination.” It's an affordable, do-it-yourself way to disinfect your well and water lines.
When To Use Shock Chlorination:
If the bacteria live in your well and your pipes then there is hope for shock chlorination to work. If the source of your bacterial problem is your groundwater or your city water system, however, then chlorinating your system will not have the desired effect and bacteria will quickly repopulate your well and distribution system.
If the bacteria not just in your well and pipes, your source water may be contaminated or you may have a running leak from a nearby septic system tank. In these cases, you will need to employ a different method for routinely controlling bacteria in your water. Rather than a “shock” treatment, you will require water treatment like UV, RO or a chlorine drip filter. Learn about water treatments.
If you’ve tested your water and detected certain types of bacterial or viral contamination, then shock chlorination is probably a viable solution for you and your home.
Disinfection by chlorine
Chlorine kills bacteria and other microbes through a process of oxidation. There are certain microbes for which this works very well, but then there are other microbes which are resistant to such disinfection by chlorine.
Microbes readily killed by chlorine:
Microbes not killed by chlorine:
Will shock chlorination work for my well?
Although the general operation and function of most drinking water wells is quite similar overall, it is important to understand that different wells will employ different systems and components. While we do provide a solution for the most common types of drinking water wells, it is possible that your well has idiosyncrasies which our instructions may overlook.
Shock Chlorination Advisory: Don’t drink the water!
The shock chlorination method is a common procedure for disinfecting drinking water by adding a very high amount of chlorine to a water system. Here are some very important things to read through and understand before performing shock chlorination on your water.
Do NOT drink (or use) the water during disinfection
During the disinfection process, NO water from the system is safe to drink or consume in any manner. No human beings or animals should be in contact with the water during a period of at least 12 hours after beginning the shock chlorination process. If possible, no toilets or faucets should be used at all during this time.
Are you ready? Pre-shock chlorination checklist
To confirm you have a coliform or e.coli or other bacterial problem. This Total Microbiology Water Test will be just the test to help. This all-inclusive pathogen and microbiological screening provides identification and enumeration of thousands of species of bacteria, protozoa, algae and more in well water.
Liquid household bleach
Must have 5.25% chlorine for disinfection to work properly.
Do not use bleach with anything else added like fragrance or scent. As a rule of thumb, 1 gallon of bleach can disinfect an 8-inch diameter well holding approximately 100 feet of water.
Large bucket, 10 gallon volume
You’ll use this to mix your bleach with water so that you have more disinfectant solution to work with and promote better mixing.
Garden hose (or equivalent)
This you’ll use to wash down your well and circulate your disinfectant.
Well Water Chlorine Shock Disinfection Instructions
Step 1 - Locate Your Well
Locate your well, remove the sanitary seal, or access plug.
Step 2 - Calculate the amount of chlorine
Use the table below to determine how much chlorine bleach you will need for disinfection. If you have a recent Water Well Bore Report then you can look at it to see how deep your well is and how high the water level is. Otherwise, you can use this table to estimate the amount of chlorine bleach you will need:
Step 3 - Preparing your chlorine bleach
With the right amount of chlorine bleach for your well measured out, mix it with some regular water so that you have more volume of disinfecting solution to work with. Having more volume will help to ensure your disinfectant is properly mixed throughout the well surfaces.
To this end, we advise that you prepare 4 and 8 gallons of chlorine bleach and water mixture in your 10 gallon bucket.
Step 4 - Pour your mixture into the well
Pour the disinfection chlorine contents down your well casing. If the 10 gallon bucket is too difficult to lift then use smaller buckets to scoop from your big bucket down into the well (make sure you’re wearing your gloves!) Try to pour the liquid in a circular motion to promote as much mixing as possible.
Step 5 - Circulate the disinfecting chlorine in a hose loop
Now that the chlorine is in the well, it is time to circulate it around so that the whole well gets disinfected.
Connect one end of a hose to a nearby spigot that draws from your well. Drop the other end of this hose down your well casing. Turn on the water at the spigot. You’ve just created a circular loop: well water goes from the well to your spigot, through the hose, and back into the well.
After 15 minutes of circulating the well water, you should smell a rather strong chlorine odor and perhaps see the water changing color. Once you notice the smell, you can turn off the spigot and remove the hose.
Step 6 - Run your disinfectant solution throughout your system
First, be sure that you have disconnected or bypassed water filters and other chlorine sensitive equipment throughout the house.
To run disinfectant through your system:
- Go to every faucet around the house, one by one, and run your water until you can smell chlorine coming out of the faucet. As soon as you are sure that the chlorine disinfectant is coming out of the faucet, you can turn it off and head to the next one.
- Go to every toilet around the house and flush it.
- Go to your water heater tank and drain it let it refill with the chlorine shocked water.
If at any point while you are running faucets you are unable to detect the smell of chlorine, go back to the well and add an additional half gallon of chlorine bleach to 10 gallons of water and repeat Step 4.
Step 7 - Let it be
Once you’ve run your disinfectant chlorine solution to every faucet in the house (and confirmed the smell of chlorine), then you are ready for the long wait. We suggest letting the chlorine stand in your pipes and well for at least 8 hours. 12 hours is preferable.
During this time, make sure that nobody uses any of the water in your house for anything. It will be dangerous to drink, and harmful if your skin touches it. Make sure you have water for people and animals.
Make sure you turn off automatic sprinklers too because high chlorine concentrations are not good for your plants.
Step 8 - Flush it out
Once you’ve waited 8-12 hours before using the water in your home, we can assume that any bacteria in the system has been killed. It is now time to dump out all of your chlorine water from the system.
Head outside and run your water out of the lines from an available spigot, preferably one with a hose. Dispose of this water away from any plants. Do not drain this water into your septic system.
Keep the water running until you no longer smell any chlorine. This may take twenty minutes or more. You can also flush all of the faucets around the house for a few minutes so that they no longer smell of chlorine.
Step 9 - Test your water to make sure treatment worked!
After one week we suggest you perform another bacterial water test to confirm that your chlorine shock treatment has been successful.
After two months we suggest running one more test to make sure your water has not been recontaminated. If you find re-contamination, there may be another problem causing bacterial contamination.