How to Shock a Well and Treat Bacteria in Well Water

Shock a well vs filter water with UV system

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.

In fact, studies show that more than 40 percent of individual water wells are contaminated with bacteria and viruses at any given time.

If you’re one of the 19 million U.S. households on a private well, you understand that water is complicated, constantly changing, and requires regular testing.

UV Water Disinfection vs. Chlorine Shock

How to Treat Coliform, E. coli and other Bacteria in Well Water

  1. Shock Your Well Water Using Chemicals: This is a quick, temporary solution and less expensive upfront.
  2. Disinfection of Well Water Using Ultraviolet (UV) Light: This is a long-term, reliable, permanent solution for treating bacteria in well water.  
chemical well shock vs UV water disinfection system

What's the Difference Between Chlorine Well Shock and UV Water Filtration?

Authorities like the US EPA and Health Canada recognize both chlorine chemical treatment and ultraviolet (UV) light as an effective means of disinfecting a water supply.

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 expensive and time consuming.

Ultraviolet Disinfection can protect your whole home from the threat of illness-causing waterborne microbes 24/7. Installing a UV light for well water provides many benefits.

Well Shock vs. UV Light Sterilizers

Well Shocking w/ Chlorine UV Disinfection
Temporary quick fix



Long-term, effective solution that destroys 99.99% bacteria, viruses, and cysts


Essentially trouble-free; annual maintenance of UV lamp change & sleeve clean


Works 24/7 to consistently keep water safe from illness-causing microbes


Environmentally friendly - no disinfection by products and no wasted water


Indicator alarm sounds if water is not being treated


No harsh chemicals that can damage skin


No damage to well casings & pump fittings from chemicals


No dangerous gas (oxidation of organics can generate THMs, a harmful gas)


Taste and odor of water not affected


Key Takeaways

What are the Benefits of UV Water Filters?

  • 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 water treatment with a UV Treatment system (such as the IHS22-D4) provides peace of mind that your well water is being treated continuously, 24/7.

Step-by-step Instructions for Shocking a Well

How to Shock a Well with Chlorine?

Well Shock Steps
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Step 1: Turn off the power to your well pump before starting to work.

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Step 2: Clear the area around the well head and remove the cap. If the cap’s cracked or broken, you should replace it.

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Step 3: Double-check your calculations, mix the chlorine solution, and pour it down the well.

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 the depth of water well, the pH of the water, and the presence of slime or biofilm.

Shocking or chlorinating a well may temporarily correct the bacteria problem. CAUTION: If you complete the well shocking process 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 issues that may contribute to repeat contamination.  

Is Shocking a Well Safe?

If the temporary method of shocking a well with chemicals is the right method for you at this time, here are the basic steps to take for proper shock treatment.

NOTE: If you're shocking your well because of a positive bacteria test, we recommend waiting one to two weeks and test your water again. Continue to repeat the bacteria test and take steps to shock the well until bacteria is no longer present.

Is Pre-Filtration Necessary 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.

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 a chemical-free way to disinfect and creates no byproducts.

Best UV Water Treatment for Well Water

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VIQUA IHS22-D4 UV Water Treatment System
  • The Viqua IHS22-D4 inclues two integrated prefilters to improve the taste and odor of your water.
  • LED Status system indicator.
  • All-in-one UV solution boasting added layers of water filtration and treatment.
  • Safeguards ALL the water coming into your home.

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  • Compact, yet powerful design treats water with UV light, plus includes an
  • Integrated pre-filter that can remove sediment, dirt and rust for improved taste.
  • Includes a lamp replacement timer.
  • Proven UV system with premium-quality parts at a value price.
  • Treats up to 9 gpm, perfect for a home with 1-3 bathrooms.

Viqua VIQUA IHS22-D4 Integrated 12 GPM UV System with Sediment and Carbon with Lead Reduction Filters IHS22-D4-
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Viqua VH200 UV System
  • Compact, 9 gallon per minute UV water sterilizer system.
  • Inactivates Cryptosporidium, Giardia, E.Coli and Fecal Coliform.
  • Utilizes high-output lamp technology.
  • 10-year warranty on system's UV chamber.
  • Treats up to 9 gpm, perfect for home with 1-3 bathrooms.

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. Thankfully, testing is not something you need to 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 there are no warning lights on the system and you've followed the protocol below.

System power
System Power
Power is kept on 24/7 to treat all incoming water
Annual lamp change and sleeve cleaning followed
Proper pretreatment in place to protect system

How Does UV Light for Water Filtration 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 (such as the IHS22-D4), you can be confident that the water is being treated night and day, inactivating harmful microorganisms, including cryptosporidium, giardia, E. coli, legionella, norovirus, and hepatitis A virus †.


How Often Should I Shock My Well?

How often should you chlorinate your well depends on if and or 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?

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 shock 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.

How Does Well Water Become Contaminated with Bacteria?

There are many ways a water well can become contaminated with bacteria or other illness-causing microbes.

  1. Contamination from septic systems is the biggest risk to well water.

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

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

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

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

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

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

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