How to Sanitize Your Well Yourself: DIY Shock Chlorination Guide

When to Shock Chlorinate Your Well

Shock chlorination (also called "shocking" or "disinfecting" a well) is a one-time treatment that kills bacteria and other microorganisms in your well and plumbing system. It's not a permanent solution for ongoing contamination, but it's effective for specific situations.

You should shock your well when:

• A water test shows positive for coliform bacteria
• After any well repairs or pump service that opened the system
• After flooding or surface water intrusion
• When a new well is first put into service
• After an extended period of non-use
• If you notice sudden changes in taste, odor, or color

When shocking WON'T solve the problem:

• Ongoing contamination from a nearby septic system or livestock
• Damaged well casing allowing surface water infiltration
• Iron bacteria (requires specialized treatment)
• Chemical contamination (chlorine only kills organisms)

If bacteria returns within weeks of shock treatment, you likely have a structural problem with your well that needs professional investigation.

Calculating Bleach Amounts for Your Well

Getting the chlorine concentration right is important—too little won't disinfect effectively, while too much wastes bleach and extends flushing time. You'll need to know your well's diameter and the depth of water in it.

Quick Reference Chart

For standard household bleach (5-6% sodium hypochlorite), use these amounts per 100 feet of water depth:

• 4-inch diameter well: 1 quart (32 oz) bleach
• 6-inch diameter well: 2 quarts (64 oz) bleach
• 8-inch diameter well: 1 gallon bleach

Calculating Your Specific Amount

First, calculate gallons of water in your well:

Gallons = Diameter (inches)² × Depth of water (feet) × 0.0408

Then use 3 pints (1.5 quarts) of household bleach per 100 gallons of water.

Step-by-Step Shock Chlorination Process

Step 1: Prepare for 24+ Hours Without Well Water

You won't be able to use your water during treatment. Fill containers for drinking, cooking, and essential needs. Plan to do this when water demand is lowest—starting in the evening is ideal.

Step 2: Bypass or Remove Water Treatment Equipment

If you have a water softener, carbon filter, or reverse osmosis system, bypass or disconnect it before shocking. Chlorine can damage filter media and shorten equipment life.

Step 3: Access the Well

Remove the well cap. If you have a sanitary well seal (the kind bolted down with a rubber gasket), you'll need to unbolt it. Older wells may have a simple cap that lifts off. Inspect the opening for debris, insects, or rodents—remove anything that shouldn't be there.

Step 4: Mix and Add the Bleach

For safer handling, dilute the bleach in a 5-gallon bucket of water before pouring it into the well. Pour the mixture directly into the well casing. You can use a hose to help wash the chlorine down the sides of the casing.

Step 5: Recirculate to Mix Thoroughly

Connect a clean hose to an outside faucet and run it back into the well opening. Turn on the water and let it recirculate for 15-30 minutes. This ensures chlorine reaches the entire water column and coats the well casing.

Step 6: Run Chlorinated Water Through the House

Open each faucet inside the house (hot and cold) and let it run until you smell chlorine, then shut it off. Do this for every tap, shower, toilet, and appliance that uses water. This ensures the entire plumbing system is disinfected.

Step 7: Let It Sit

Replace the well cap and let the chlorine solution sit for 12-24 hours. Overnight is ideal. Don't use any water during this time—doing so will reduce the chlorine concentration.

Step 8: Flush the System

After the contact period, you need to flush all the chlorinated water out. Start with an outside faucet that doesn't go to your septic system (or run the hose to a safe area away from plants). Run until you no longer smell chlorine—this may take several hours and hundreds of gallons. Then flush each inside tap.

After Treatment: Testing and Follow-Up

Shock chlorination is only effective if you verify it worked. Follow these steps after treatment:

• Wait 1-2 weeks before retesting: Testing too soon may give false results
• Retest for coliform bacteria: Use a certified lab or home test kit
• If bacteria returns: The well may have a structural problem—call a professional
• Consider annual testing: Private wells should be tested at least once per year

When to Call a Professional

DIY shock chlorination works well for simple contamination events, but some situations require professional help:

• Bacteria returns within a few weeks of treatment
• You can't access the well safely
• The well has known structural issues
• You're dealing with iron bacteria (orange/red slime)
• The contamination source is unknown

A well professional can perform video inspection to identify casing problems, conduct more thorough disinfection, and recommend permanent solutions if contamination is ongoing.