How to Shock Chlorinate and Sanitize your Water Well

Subscribe: RSS

Note: This podcast transcript has been edited for clarity and length.

In this episode, I discuss how to shock chlorinate and sanitize your well with chlorine bleach. This is sometimes referred to as “shock chlorination” because it uses a high dose of bleach to kill bacteria, eliminate odors, and oxidize iron and other contaminants. I also explain why it is important not to add too much or too little bleach and other safety steps to follow.

What You’ll Hear in this Episode

1. What is shock chlorination?
2. Testing for bacteria and other contamination
3. Reasons for shock chlorinating your well
4. The Right Procedure in chlorinating your well yourself
5. Precautions to take in chlorinating your well yourself
6. What kind of chlorine to use in shock chlorinating your well
7. How to find a certified well contractor in your area
8. Why it’s important to mix and add the chlorine in a well-ventilated area
9. Identifying the source of well contamination
10. When to call a professional well contractor
11. When is it safe to use the water again after chlorination
12. Benefits of shock chlorinating your well

Hello! Thanks again for tuning in to the podcast. I am Gerry Bulfin, a water treatment contractor and WQA-certified Master Water Specialist. I hope you’re having a great day and that everything’s going great for you and your water.

In this podcast series, I’m providing useful, easy-to-follow tips and information, mostly about well water, well water treatment systems, and how to improve the quality of your well water.

Free Download of Guide

In today’s episode, we’ll cover the basics of shock chlorinating and sanitizing your well, pipelines, and storage tanks.I actually have a free guide for this podcast called How to Shock Chlorinate Wells, Pipelines, Storage Tanks, and Systems. This is an easy-to-follow guide with step-by-step lists of what to do and very useful charts to show you how much chlorine bleach pellets or powder to add based on the size and depth of your well.

I’m offering that free to listeners in this podcast. You can get your guide by texting the word SHOCKGUIDE, just one word, to 44222 or going to cleanwaterstore.com/podcast. You can find it there. So text the word SHOCKGUIDE to 44222, and we’ll send it to you.

Shock Chlorination

Shock chlorination means adding enough bleach—either liquid sodium hypochlorite or powdered calcium hypochlorite—to raise chlorine levels in your well to 200–300 parts per million (ppm). This high concentration kills bacteria and eliminates odors. In contrast, city water usually has only 0.2–2 ppm.

How It Works

To be effective, chlorine must remain in the well for 6–12 hours. It works best when pH is between 5 and 7. If your pH is too high, adding citric acid can help. After the waiting period, test for chlorine. If you have less than 10 ppm, repeat the process.

Chlorine gets used up by organic matter, odors, and bacteria. If chlorine levels drop too quickly, that indicates a high chlorine demand.

When To Shock Chlorinate

Shock chlorination is commonly done:

After a new well is built
Following repairs or equipment replacements
If you detect odors or slime
After flooding
When selling or buying a home
If coliform bacteria are found, shock chlorination is often the first step.

DIY or Hire a Pro?

If your well cap has an accessible plug, you might be able to do it yourself, cautiously. Otherwise, contact a licensed well contractor. Be careful not to disassemble parts you're unfamiliar with.

Watch for Sediment and Rust

After chlorination, you may see dark water from loosened sediment or rust. Don’t let this run into softeners or septic systems. Flush through an outdoor hose until the water runs clear and chlorine-free.

Choosing the Right Bleach

Use bleach certified for potable water:

Best: Dry pellets or powdered bleach (calcium hypochlorite)
Good: Liquid pool chlorine (10–12% sodium hypochlorite)
Avoid: Household bleach—it contains extra chemicals
Hydrogen peroxide is not effective for sanitizing wells.

How Much to Use

Use 2 oz of pellets per 100 gallons for 100 ppm. Kits often include pellets and powder. Refer to your well log for depth and volume, or use online tables to estimate chlorine needs.

The Procedure

Bypass softeners and filters.
Clean the well house and equipment.
Remove the well cap and measure the water depth.
Mix bleach with 5–10 gallons of water.
Pour the mix and drop pellets into the well.
Circulate water using a hose until chlorine smell is strong.
Let water sit 6–12 hours.
Flush system through an outside faucet.
Retest in 2–3 weeks for coliform bacteria.

Safety Tips

Wear gloves, goggles, and waterproof boots
Work in a ventilated area
Keep pets and children away
Turn off the pump circuit breaker before opening the well

How Much Water to Flush

Flush 4 well volumes before drinking. For a 4-inch well at 200 feet, that’s about 600 gallons. Larger wells need more. This helps clear disinfection byproducts like trihalomethanes and reduces risks from metals like arsenic.

What If Bacteria Returns?

If coliform returns after one or two shock treatments, contamination may be ongoing. It could be from a cracked cap, poor seals, or proximity to a septic tank. Call a professional to investigate.

Get More Help

For a full guide, visit cleanwaterstore.com/podcast and look for Episode 7. Or text SHOCKGUIDE to 44222 for a free download. It walks you through the full process and helps eliminate odors, iron, and bacteria from your well water.

Have a Storage Tank? Learn How Much Chlorine To Add to Storage Tanks to Kill Bacteria

Like, Share, and Join Our Community