When Bacteria Threatens Your Well Water: The Essential Guide to Shock Chlorination

Well water contamination by bacteria is one of the most common water quality problems facing private well owners today. Shock chlorination is the most widely recommended means of treating bacterial contamination in home water systems. This powerful disinfection process can eliminate harmful bacteria and restore your water’s safety, but knowing when and how to perform it correctly is crucial for protecting your family’s health.

Understanding Shock Chlorination

Shock chlorination is the process by which home water systems such as wells, springs, and cisterns are disinfected using household liquid bleach (or chlorine). Shock chlorination is a process of disinfecting a private water supply and plumbing system by circulating a concentrated chlorine solution throughout the system. The process involves introducing high levels of chlorine into your entire water distribution system to kill bacteria, viruses, and other harmful microorganisms.

Shock chlorination introduces very high levels of chlorine into a water system. During the disinfection process, water from the system is not suitable for consumption or extended contact by people or animals.

When Should You Shock Chlorinate Your Well?

Several situations require immediate shock chlorination of your well water system:

• Wells should be shock chlorinated when a well water sample result shows that there is bacteria in the water.
• Shock chlorination is required following well construction and is recommended following a positive total coliform water test or any maintenance or repair of a private water supply system.
• Upon completion of a new well or after pump replacement or repair. When the distribution system is opened for repairs or maintenance or when the system has not been used on a regular, i.e., weekly basis. Following contamination by flood water, a contamination incident, or damage to the system.
• Any time a well is opened for repair it must be disinfected. Newly-built wells should also be shock chlorinated following construction.

However, some positive bacteria tests are the result of a less serious, one-time contamination incident. For example, bacteria may be introduced when a new submersible pump is installed in a well or from surface runoff during an unusually heavy rainfall. Shock chlorination is a simple and inexpensive process that can be used to disinfect water supplies that have been contaminated as a result of these one-time contamination incidents.

Essential Safety Precautions

Before beginning the shock chlorination process, several critical safety measures must be taken:

Concentrated chlorine solutions like those required to shock chlorinate a private water system can be dangerous. It is important to wear appropriate clothing, including goggles, a protective apron, and rubber gloves and boots. The area where the chlorine solution is to be mixed and added to the water supply must be well-ventilated.

Your water pump is electric. To prevent an electric shock, turn the pump circuit breaker off before removing the well cap or cover. You will need to turn the power on during Step 3 of the shock chlorination process (below), but be sure to turn the pump circuit breaker off again before replacing the well cap or cover (Step 4).

It is critical to plan ahead and have a 12 to 24 hour supply of nonchlorinated water to use for drinking and cooking during the shock chlorination process. It is important NOT to use any water from your supply system during the shock chlorination process.

Protecting Your Water Treatment Equipment

Shock chlorinating a water supply system can potentially damage components such as pressure tanks, some filters and filter media, and other treatment devices. Before you begin, disconnect all carbon filters and reverse osmosis units attached to your household water lines. The strong chlorine solution can damage these filters.

For homeowners in Central Florida who rely on comprehensive water treatment systems, consulting with professional services like well water filtration Lake County, FL specialists can ensure proper equipment protection during the disinfection process.

The Shock Chlorination Process

Use the plain (and generally least expensive) unscented household chlorine bleach with at least 5% sodium hypochlorite found in supermarkets; do NOT buy fresh scent, lemon or other scented chlorine products. When using ordinary laundry bleach, 3 pints should be added for every 100 gallons of water in the well.

The basic process involves:

1. Calculating the proper amount of bleach based on your well’s diameter and water depth
2. Mixing the chlorine solution and adding it to the well
3. Circulating the chlorinated water throughout your entire plumbing system
4. Wait 6-12 hours for the chlorine to work, then flush the chlorinated water from your well and pipes.
5. Running all faucets until you smell chlorine at each outlet
6. Allow chlorinated water to stand in the well and pipes for at least 8 hours (preferably 12 to 24 hours).
7. Flushing the system until chlorine odor dissipates

Post-Treatment Testing and Follow-Up

Proper testing after shock chlorination is crucial to ensure the treatment was successful. After completing shock-chlorinating the water supply system as outlined in this publication, wait for 5–7 days with a discharge of 250–280 gallons of water each day to retest for total coliform and E. coli bacteria. Follow sample collection instructions carefully. If the test results show the absence of coliform bacteria, the water is safe to drink.

Approximately 2 weeks after flushing the system, sample the water (according to laboratory instructions) and have it tested for biological contamination. Repeat the test in 2 to 3 months to be sure the system has not been recontaminated.

When Shock Chlorination Isn’t Enough

However, if test results show the presence of coliform bacteria, the source(s) of contamination should be identified and eliminated through a licensed well driller/contractor or a continuous disinfection treatment system should be installed.

A recent Penn State study of wells contaminated by coliform bacteria found that shock chlorination and installation of a sanitary well cap successfully removed the bacteria for one year in 15 percent of the wells. This procedure was most successful in wells that had small numbers of coliform bacteria (fewer than 10 colonies per 100 mL) and no E. coli bacteria.

Although shock chlorination will address bacteria present in your water system, if a continuous source of contamination persists — a malfunctioning septic system or a pathway for surface water to enter a well, such as a loose well cap or cracked casing — bacterial contamination will continue to be a problem. Steps should be taken to identify and address the source of contamination.

Professional vs. DIY Approach

While an accomplished do-it-yourselfer can shock chlorinate his or her own private water supply system, the process can be challenging. If your water supply system needs to be shock chlorinated, consider contacting a licensed and certified well driller to do it for you.

For Florida residents seeking comprehensive water treatment solutions, Quality Safe Water of Florida offers professional expertise in water system disinfection and maintenance. Quality Safe Water of Florida is dedicated to ensuring every Florida family has access to clean, safe, and purified water. We are committed to providing the highest quality, efficient, and affordable water treatment solutions, prioritizing the health and well-being of our customers. We are a Florida-based water treatment company that delivers top-tier solutions for residential and commercial clients. Our unwavering commitment to quality and customer satisfaction sets us apart. We take pride in offering the highest quality, safe, and reliable water treatment systems.

Conclusion

Shock chlorination is an essential tool for maintaining safe well water, but it requires careful planning, proper execution, and thorough follow-up testing. Shock chlorination is the most effective way to eliminate harmful bacteria in wells. Whether you choose to perform the process yourself or hire professionals, understanding when and how to shock chlorinate your well water system is crucial for protecting your family’s health and ensuring access to safe, clean drinking water.

Remember that shock chlorination is most effective as a response to one-time contamination events. If bacterial contamination persists after proper shock chlorination, it’s time to investigate deeper issues with your well system and consider installing continuous disinfection treatment systems to ensure long-term water safety.