How to Shock a Well

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As a private well owner, it’s your responsibility to maintain your well and make sure it’s safe to drink from. You don’t have the advantage of having your water treated for you by your local authority, which means it’s down to you to make sure your water is continuously free from bacterial contamination throughout your well’s lifespan.

A positive test for contamination can be scary, but it’s easy enough to solve the problem with shock chlorination.

In this guide, I’ll help you to understand the ins and outs of shock chlorination, allowing you to confidently take the appropriate steps for the health of your family.

🤔 What is Shock Chlorination?

Shock chlorination involves treating your well with a chlorine solution in order to kill bacteria.

It’s a quick and effective method of disinfection if you’ve discovered that your well is contaminated with bacteria. Iron bacteria, coliform bacteria and e. coli are the three most common types of bacteria that are likely to be found in a well.

📆 How Often Should You Shock Your Well?

The frequency of how often you use shock chlorination for your well depends on a number of factors. Generally, it’s wise to shock your well every 3 to 5 years, after testing your water for contamination.

Aside from that, you should shock-chlorinate your well in any of the following circumstances:

  • You’ve constructed a new well water system
  • Your well has been contaminated with floodwater
  • You’ve had to open your well to carry out repairs
  • You’ve tested your drinking water supply and discovered bacterial contamination
  • You’ve had plumbing or piping work done
  • You have replaced your well’s pressure tank, holding tank or pump
  • There’s slime in your well water that indicates iron bacteria
  • Your drinking water has taken on an odor that indicates sulfur bacteria
  • You’ve discovered that your well water runs near a septic tank, or you’ve received word of a malfunctioning septic system
well water diagram
source: United States Environmental Protection Agency (EPA)

🔠 Type of Chlorine Bleach to Use to Shock a Well

The most common shock chlorination options available involve the use of dry chlorine pellets, chlorine granules, and liquid chlorine bleach. All options are relatively affordable, costing less than $20 for the job.

Dry Pellets

Dry pellets that contain 70% calcium hypochlorite are ideal for shock chlorination of wells, cisterns and storage tanks. The exact number of pellets required will be determined by how much water the well contains. Dried pellets tend to be the easiest and safest treatment option.

Dry Chlorine Granules

Dry chlorine granules are very similar to dry pellets. You simply add a measured amount of granules to standing water and pour the solution into your well system. This is another safe and easy treatment option that’s worth considering.

Liquid Chlorine Bleach

You can use bleach for disinfecting your bathroom to clean your well, and this is generally an affordable option – most of us have a stock of bleach in our cupboards already.

If you’re using liquid chlorine bleach to shock your well water, make sure to use a plain, unscented bleach with a minimum of 5% sodium hypochlorite.

Keep in mind, too, that chlorine solution is a little more dangerous to use for water treatment, and requires protective gear for the process.

1️⃣ How to Shock Chlorinate a Well Using Dry Chlorine Pellets or Granules

When carrying out shock chlorination of a well, you ideally should aim for a chlorine concentration of 100 PPM.

You can produce this by measuring out two ounces of chlorine pellets or granules for every 100 gallons of water you’re treating.

Note that well water with a particularly high sulfur or iron content may require slightly higher levels of chlorine.

To shock your well with chlorinated water, follow the below steps:

  1. Make sure your treatment bypasses any water filters, softeners or purification systems. Clean out the equipment you’ll be chlorinating, including the spring house, storage tank, well house and reservoir. Make sure you wash away any sediment, dirt or debris that may have built up on the inside surfaces. Pump your well to get rid of any lingering foreign or suspended materials. Scrub the inside or your equipment with a cloth and a water-chlorine mix (preferably half a gallon of household bleach for every 5 gallons of water).
  2. Lift the plug that’s used for inspection on the top of your well. Your well might have no inspection hole, especially if it has a buried pressure tank or pitless adapter. Take the well cap or seal off and measure the depth of your water. From this, you can determine how much chlorine you’ll need. Use table below will help you with your calculations.
  3. Fill a 5-gallon container with standing water, then measure out the pellets or granules needed and add them to the container. Always add the pellets to standing water and not the other way around. Next, carefully pour the solution into your well system. This will clean the upper part of the well.
  4. To make sure the chlorine is thoroughly mixed throughout the well system, attach a garden hose to the well’s hose bib (it should be near to your pressure tank) and send water back down your well system. This will also give the upper area of the well a rinse. Once around 15 minutes have passed, you should detect a strong chlorine odor. Check your hot water faucets for a strong chlorine odor. Be patient – but if you can’t detect a chlorine smell after 20 minutes, you may need to mix up some more.
  5. Let your chlorinated water sit in the well system for a minimum of 6 hours. If you can leave the water overnight, even better. Once the time has passed, open any outside faucets/ turn on a garden hose and allow your system to flush until the strong chlorine odor is no longer present. Repeat this process with every faucet in your home. Don’t run high levels of chlorine into your septic system.
Well Casing Diameter (inches)Gallons of Water/ 100 FeetOunces of Granules for 100 PPM# of Pellets for 100 PPM
8 - 122605.1183
12 - 1659011.6415
20 - 242,350461,654
30 - 365,2901043,724

2️⃣ How to Shock Chlorinate a Well Using Liquid Chlorine Bleach

  1. Again, start by cleaning the components of the well system you plan to shock chlorinate, following step 1 above. Scrub away any debris with a household bleach mix and use the pump to remove any lingering foreign contaminants.
  2. Your next job is to figure out the amount of chlorine you require for disinfection. For this, you’ll need to know the depth of water in your well. Check out the table below to find out how much 5% household bleach you should use (for pool bleach, which is usually about 10-12%, use half the stated amount).
  3. In a large container, combine your chlorine solution with a minimum of 10x the amount of water. You shouldn’t pour high levels of chlorine down the well system – it should always be diluted first.
  4. Remove the well cap and the seal (if your well has one). Seek professional advice before doing this if you’re unsure, especially if you have to remove a sanitary seal.
  5. At this stage, if your well has a packer jet pump, you’ll need to remove the pump, jet unit and pipe before you can properly disinfect your system.
  6. Pour the chlorinated water solution carefully into the well, making sure to stay protected from splashes and chlorine fumes. Additionally, you should avoid directly pouring the chlorine onto the well’s wire connectors at the pump.
Well Casing Diameter (Inches)Water Depth (feet)
0 - 5050 - 100100 - 200200 - 300300 - 400400 - 500
48 oz16 oz24 oz1 qt1.5 gal2 gal
61 qt 2 qt.1.5 gal2 gal2.5 gal3 gal
8 - 121 gal1.5 gal2 gal2.5 gal5 gal6 gal
12 - 161 gal2 gal4 gal6 gal8 gal10 gal
20 - 242 gal6 gal10 gal14 gal18 gal22 gal
30 - 366 gal10 gal20 gal30 gal40 gal50 gal

🔆 UV: An Alternative to Chlorinated Water for Well Disinfection

Shocking a well takes some effort, and not everyone likes the idea of drinking chlorinated water – even if most of the chlorine should dissipate if you leave plenty of time after the chlorination process.

There’s an alternative to chlorinating a well that requires no chemicals, produces no chlorine smell and works instantly to eliminate the bad stuff from your drinking water – I’m talking about UV disinfection.

UV disinfection uses a UV lamp to kill bacteria and other pathogens in water. When water flows through the UV chamber, the UV light will effectively destroy more than 99.9% of bacteria, viruses and protozoa – even some pathogens that are resistant to the chlorination process, like Giardia.

There are a number of advantages of UV water treatment for your well water system rather than chlorine. You won’t have to worry about the amount of bleach you’re using, for one, as you’re using a failsafe method of disinfection.

You also won’t have to wait for 12 to 24 hours for the water treatment to work, as UV works instantly.

You won’t have to protect yourself with rubber gloves and other protective gear if you opt for a UV disinfection water system – and, in fact, you won’t have to do anything yourself, as the lamp will automatically clean your water as it flows through it.

UV is a safe way to disinfect drinking water, and you can use it as a primary means of disinfection for your home’s plumbing system if you prefer. In the US, UV disinfection is approved by the EPA, so you can rest assured that this is an effective method of eliminating bacteria and improving water quality.

UV System installed on whole house filter
Whole house water treatment + UV disinfection diagram

❔ Frequently Asked Questions

How long will I have to wait before I can use my well after shock chlorination?

The exact waiting time ranges from 30 minutes to 24 hours after you’ve added the chlorine and allowed it to circulate through your household plumbing system, including your pipes, pressure tank, and hot water heater. You’ll have to flush your whole water system once the period of 24 hours has passed, then do a test of your water in the well system again to check that the chlorine solution did its job. If your water is free from bacterial contamination once more, you’re good to start drinking it again.

Is it safe to shock a well?

Yes – though you should take appropriate care when handling the chlorine solution. Be sure to follow the manufacturer’s instructions and wear protective/safety gear if you have any. Don’t add too much chlorine to your well water – this could prove dangerous. You can always use a chlorine test kit to detect chlorine levels in your well water supply for extra reassurance.

It’s also worth noting that shocking your well system doesn’t provide a permanent solution. About 1-2 weeks after shock chlorination, you should test your well water supply again. If bacteria is present, this points to a bigger problem that may require solving, such as a nearby leaking septic tank or a cracked well casing.

Will water filters remove bacteria?

No. You may use whole-home carbon filters to filter your well water. While carbon filters are effective at removing certain well water contaminants, like sediment and VOCs, they typically don’t have a small enough pore micron size to remove pathogens as small as bacteria.

How can I be sure that shocking my well worked?

Test the water in your well for contamination after you’ve completed the shock chlorination process. A water test will let you know whether the process has worked or not.

  • Michael Claybourn
    Water Treatment Specialist

    With 25+ years in water treatment, Michael Claybourn Sr. (WT Specialist 3) leads his company, Water of Texas LLC, in solving industrial, commercial, and residential water challenges. From filtration to ozone, he tackles any task, from initial consultation to equipment maintenance. His passion, honed in nuclear power and Culligan of Brazosport, fuels his commitment to delivering pure, healthy water for every client.

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