Chlorine is one of the most effective and affordable disinfectants for well water systems. Homeowners and municipalities rely on it not only to purify water but also to sanitize surfaces, pipes, and storage tanks.

But how much chlorine do you really need—and how much is too much?

Step 1: Clean the Tank First

Before adding chlorine, clean the tank thoroughly:

• Remove any debris or sediment.
• Scrub interior surfaces to eliminate dirt and buildup.
• If needed, pump out suspended solids or floating matter.

Step 2: Scrub With a Strong Chlorine Solution

Use this guideline for creating a chlorine cleaning solution:

• Mix ½ gallon of household bleach or ¼ gallon of pool chlorine with every 5 gallons of water.
• Use this to scrub all interior surfaces.

Step 3: Check for Structural Issues

Inspect your tank for:

• Cracks or leaks around the lid, vents, or manway.
• Missing screens or unsealed lids that allow insects or debris to enter.

Proper sealing prevents contamination after cleaning.

Step 4: Add the Correct Amount of Chlorine

Refer to a chlorine dosage chart to add the right amount of bleach based on your tank size.

• For regular disinfection, bring chlorine levels to 5–10 ppm and let it sit 12 hours or more.
• For faster results, use 50–100 ppm and let it sit for 2–6 hours (shock chlorination).
• Afterward, drain and flush the tank. Do not flush chlorinated water into septic systems or natural water sources.

Extra Tips

• Avoid steel tanks for repeated chlorination—they can corrode and leak over time.
• If your well produces little water, consider hauling water in to avoid overworking it.
• Sanitize at least once a year to keep bacteria and sediment buildup under control.

Preparing the Storage Tank

Before you begin the sanitization process, it is crucial to prepare your storage tank properly. Start by physically cleaning the tank to remove debris, sediment buildup, or other contaminants. This can be done by hosing out the tank and scraping off any stubborn deposits. For tougher stains, a wire brush can be very effective. Additionally, inspect the tank for any cracks, leaks, or other damage that could compromise the disinfection process. Ensuring your tank is clean and intact will make the chlorine treatment more effective.

Choosing the Right Chlorine Solution

Selecting the right chlorine solution is key to effectively sanitizing your storage tank. Household bleach is a common and effective disinfectant, but choosing a bleach specifically designed for water treatment is important. Opt for a non-scented, NSF-approved household bleach with a concentration of 5.25% chlorine. Avoid bleaches with additives or fragrances, as these can contaminate your water. Using the right type of bleach ensures that your water remains safe and clean.

Determining the Correct Chlorine Concentration

Getting the chlorine concentration right is critical for effective disinfection. A chlorine concentration between 1 and 2 parts per million (ppm) is recommended for most storage tanks. However, the exact concentration needed can vary based on the size of your tank, the type of water being treated, and other factors. Consulting with a water treatment professional can help you determine the precise chlorine concentration required for your specific situation. This ensures that your storage tank is properly sanitized without overdoing it.

Sanitizing the Storage Tank

Once you’ve prepared your tank and chosen the right chlorine solution, it’s time to sanitize. Add the chlorine solution to the tank at the recommended concentration. Mix the solution thoroughly with the water in the tank to ensure even distribution of the chlorine. Allow the tank to stand for at least 30 minutes to let the chlorine disinfect the water. After the treatment period, flush the tank to remove any residual chlorine. This step is crucial to ensure that the water is safe for use.

Post-Treatment Precautions

After sanitizing your storage tank, it is important to take a few post-treatment precautions to ensure the water is safe for human consumption. First, thoroughly flush the tank to remove any residual chlorine. Next, test the water for free chlorine residual to ensure it is within the recommended range. Regularly inspect the tank to ensure it remains clean and free of contaminants. By following these steps, you can maintain a safe and efficient water storage system.

Resources:

Also, Read Our How-To Guide: How Much Chlorine To Add to Storage Tanks to Kill Bacteria

Frequently Asked Questions (FAQs)

1. How often should I sanitize my water storage tank?

We recommend cleaning and sanitizing your storage tank at least once a year. If you notice odor, sediment buildup, or bacteria in your water, sanitizing more frequently is a good idea. After chlorination, ensure the water is drained into the distribution system to manage water quality for safe consumption.

2. What kind of chlorine should I use for disinfecting my storage tank?

Household bleach (5–6% sodium hypochlorite) works well for most home systems. Pool chlorine can also be used but should be diluted carefully. Always refer to the chart for the correct dosage. Regularly inspect and disinfect your water tank to maintain its integrity and prevent contamination.

3. Can I use too much chlorine in my tank?

Yes—too much chlorine can corrode pipes, damage components, and leave an unpleasant taste or smell. Based on your disinfection goals, stick to the recommended parts per million (PPM) levels.

4. Is chlorine safe to use in drinking water systems?

When used in the correct dosage and flushed properly after disinfection, chlorine is safe and approved for use in potable water systems by the EPA and CDC.

5. What if I don’t want to use chlorine?

There are alternative methods like hydrogen peroxide or ozone injection, but chlorine remains one of the most accessible and affordable options for well water treatment and storage tank disinfection.