How to Shock a Well

Do You Have Coliform Bacteria in Your Well Water?

Your well water may have tested positive for coliform bacteria and you're seeking a solution. Bacteria, including total coliform bacteria, iron bacteria, and E. coli are commonly found in private wells.  

If you’re one of the 19 million U.S. households on private well, you understand that water is complicated and constantly changing. Bacterial contamination of private wells is common, and studies show that more than 40 percent of individual water wells are contaminated with bacteria and viruses

chemical well shock vs UV water disinfection system

How to Treat Bacteria in Well Water? 

Two options for treating bacteria in well water: 

  1. Shock Your Well Water Using Chemicals:  A quick, temporary solution and less expensive upfront. 
  2. Continual Disinfection of Well Water Using Ultraviolet (UV) Light:  Reliable, long-term, permanent solution.   

Difference Between Chlorine Well Shock and UV Water Filtration

What are the differences in shocking a well with chlorine versus ultraviolet disinfection for well water treatment? 

Authorities like US EPA and Health Canada recognize both chlorine and ultraviolet (UV) light as an effective means of disinfecting a water supply. Check out this video explaining UV Water Disinfection vs. Chlorine. Comparison of UV well shock with chemicals vs UV water sterilize

Well Shocking means high levels of chlorine are introduced into the water source and plumbing system for a temporary period in order to kill bacteria. While shock chlorination is a relatively economical, "quick fix" to treat bacteria in a well, the solution is only temporary and not always reliable. It also requires re-testing, which can become very expensive.

Ultraviolet Disinfection can protect your whole home from the threat of illness-causing microbes in your water. Installing a UV light for well water provides the following benefits:

  • UV light for well water provides a long-term reliable method of treating well water by running the water over a UV light that kills bacteria and viruses
  • This process of exposing water to UV light is simple but effective, and destroys 99.99 percent of harmful microorganisms, including some that are chlorine resistant (such as Cryptosporidium and some forms of Giardia). 
  • No chemicals added with UV disinfection, so there is no change to the taste or odor of your water. And, with UV, you don’t have to handle noxious chemicals, monitor the chemicals, or worry that someone in your home will become sick. 
  • Well Treatment with a UV Disinfection system (like the Viqua IHS12-D4 or IHS22-D4) provides peace of mind that your well water is being disinfected continuously, 24/7.

    How Often Should I Shock My Well?  

    How often should you chlorinate your well depends on if and when bacteria is present. Since you can’t see, smell, or taste bacteria in your water, you'll need to test your well water often.

    With chemical shock treatments, the process will need to be repeated every time bacteria is present, understanding that even after you’ve shocked your well, re-tested, and received a clear "total coliform test", you might need to repeat this process again and again. 

    How Long Does it Take for a Well to Clear up After Disinfecting Well? 

    With chemical well shocking, once you’ve added the chlorine and circulated through the plumbing system, you should wait 12-24 hours before using your water.  

    After flushing the whole system, you should test your water again to make sure the shocking was effective, and your water is free of bacteria. But keep in mind that water quality is NOT static and it changes throughout the year – even from day to day.  

    With a UV system, your water is disinfected instantly, as it runs through the stainless steel chamber. It doesn’t address the contamination in the well itself, but instead treats the water as it enters the home, destroying 99.99% of microorganisms. 

    Is Shocking a Well Safe?

    Shocking or chlorinating a well may temporarily correct the bacteria problem (or taste and odor issues). One to two weeks after shocking, you should test the water again for E. coli, iron bacteria, and coliform bacteria. Also, CAUTION: If you do the shocking yourself, keep in mind that chlorine is corrosive and should be handled with care. If you’re uncomfortable handling corrosive chemicals and dealing with plumbing systems, consider calling a water treatment professional. An expert will know exactly how to solve your water issues and can also identify well deficiencies that may contribute to repeat contamination.  

    How to Shock a Well with Chlorine? 

    With the short-term solution of treating bacteria with chemicals, how much bleach, hydrogen peroxide or chlorine is needed to shock a well will vary, depending on: 

    • Depth of water well 

    • pH of the water 

    • presence of slime or biofilm 

    Step-by-step Instructions for Shocking a Well

    If the temporary method of well shocking with chemicals is the right method for you right now, here are the basic steps:  

    Step 1: Turn off the power to your well pump before starting to work. 
    Step 2: Clear the area around the well head and remove the cap. If the cap’s cracked or broken, you should replace it. 
    Step 3: Double-check your calculations, mix the chlorine solution, and pour it down the well. 
    Step 4: Circulate the water by connecting a hose to the faucet closest to the well. Put the other end of the hose in the well and open the faucet. Turn the pump back on and wash down the inside of the well casing for about 15 minutes. Once you’ve finished washing down the well, open all the faucets inside and outside the home. Run the water until you can clearly smell chlorine, and the shut off the tap. Don’t forget to flush all the toilets. If there isn’t a strong chlorine smell, add more chlorine to the well and repeat the steps to this point. 
    Step 5: Turn the power off on the well pump again. Close and seal the well cap and let everything sit for 12-24 hours. 
    Step 6: After 12-24 hours, flush the chlorine from the plumbing system. Open the outside faucets first, then the ones inside. Let each faucet run until you can no longer smell chlorine. It can be tough to properly flush chlorine from a hot water tank, so you may want to drain it after flushing the system. 

    If you were shocking your well because of a positive bacteria test, wait one to two weeks and test your water again. 

    Is Pre-Filtration Needed in Treating Well Water?

    When it comes to well water, it may be necessary to have a water softener installed before the UV system to treat calcium that causes “hard water”. Hard water can build up scaling on the UV lamp sleeve, which decreases the efficacy of the ultraviolet process. Testing for minerals and installing the necessary pre-treatment is essential in order to achieve optimal disinfection of your water. 

    Also, if your water smells or tastes swampy, musty, or oily, is yellow or reddish brown, and there’s rust-colored slime deposits in standing water, you could have iron bacteria in your water. Contact your local water treatment professional for advice. The water expert can also test for hydrogen sulfide and manganese. 

    How Does Well Water Become Contaminated with Bacteria? 

    • Contamination from septic systems is the biggest risk to well water. Sources of well water contamination from

    • Water levels in a well rise and fall over time, introducing new opportunities for bacterial growth.  

    • Seasonality plays a significant role, with a general increase in well water contamination in the Spring due to thawing snow runoff. 

    • Significant rainfall and flooding can introduce bacteria to a private well. 

    • Manure from large-scale animal feeding operations is a threat to drinking water. 

    • Run-off from fertilizers and pesticides is a common concern of well owners. 

    • Poorly constructed, cracked or unsealed wells can provide a path for bacteria to enter groundwater and contaminate your well. 

    This short video explains more about how microbes enter well water. (Image courtesy

    UV water filter for well water

    Is UV a Safe Way to Treat Water?  

    UV technology has been used for decades by municipal water suppliers and commercial water bottling plants. Because ultraviolet is safe, economical and reliable, millions of homes and businesses now use UV technology to disinfect their water. 

    In fact, many municipalities are now using UV light as their PRIMARY method of disinfection, and use chlorine as a secondary disinfectant to maintain low bacteria levels in distribution lines. 

    While most skin cancers are a result of exposure to UV rays in sunlight, the UV rays in water disinfection do NOT cause cancer. The process of exposing water to UV light to well water takes place in an enclosed stainless-steel chamber, posing no risk to family or pets. 

    UV disinfection is an environmentally-friendly disinfection method approved by the US EPA and is . It is a chemical-free way to disinfect and creates no byproducts.


    How to know if a UV system is working properly? 

    To tell for sure if your UV system is disinfecting properly and killing all the bacteria in your water, test your water. If the test shows no bacteria, you can rest assured the UV system is doing its' job. But testing is not something you can do every day. 

    UV systems generally have both audible and visual alarms to let you know if the system isn’t working properly. Some UV systems even feature a UV sensor that measures the intensity of the UV lamp, ensuring there’s a high enough UV dose to provide optimal disinfection.  

    You can be confident your UV Light for Well Water system is working correctly if:

    • the power of the UV system is on
    • you keep up with scheduled maintenance of changing the lamp every year
    • you clean the quartz sleeve each year, replacing it every 2 years
    • you have the proper pre-treatment in place
    • There are no alarm signals on your UV unit

    How does UV water filter work

    How Does UV Work? 

    UV is a physical disinfection process. It gets the job done with UV-C light. In a nutshell, UV light sterilizes organisms as they pass through a stainless steel chamber of the UV system, and leaves the microorganisms unable to reproduce. If an organism cannot reproduce, the organism dies.  

    The preeminent method of controlling organisms in your water is at the point-of-entry into the home with a whole-home water disinfection system. When you install an ultraviolet water treatment system (like the Viqua IHS12-D4 or IHS22-D4), you can be confident that the water is being disinfected night and day, destroying 99.99% of harmful microorganisms, including cryptosporidium and giardia, which are highly resistant to chlorine.