How do I disinfect my well after flooding?

The standard procedure is shock chlorination: calculate chlorine amount based on well depth/diameter, turn off power, remove well cap and add chlorine solution, run water through all fixtures until you smell chlorine, wait 12-24 hours without using water, flush system until chlorine smell is gone, wait 1-2 weeks, then test for bacteria. If contamination persists, repeat the process or consult a professional. For severe flooding with mud/debris in well, professional service is recommended.

When should I call a professional for flood-damaged well?

Call a professional if: floodwater entered the well casing directly, you see mud or debris in the water, the well pump won't run or runs strangely, water remains contaminated after shock chlorination, you're not comfortable performing chlorination yourself, the well was submerged for an extended period, or you notice structural damage to the wellhead or casing. Professional equipment can properly flush debris and verify system integrity.

Can I just let my well 'clear up' naturally after flooding?

No—never assume flooding contamination will resolve on its own. While sediment may settle and water may appear clearer, bacteria and pathogens can persist indefinitely. Untreated flood-contaminated wells have caused serious illness and even death. The well must be properly disinfected, and water must test negative for bacteria before it's safe to drink. Natural flushing doesn't eliminate pathogens.

Well Disinfection After Flood: Emergency Restoration Guide

Q: Is my well contaminated after a flood?

If floodwater reached your wellhead or submerged any part of your well system, assume it's contaminated. Even if water didn't directly enter, flooding can push contaminated groundwater into your aquifer, saturate soil around the casing, and introduce bacteria through compromised seals. Do not drink the water until it has been disinfected and tested negative for bacteria. Use bottled water for drinking, cooking, brushing teeth, and making ice.

Q: How long should I wait to use well water after disinfection?

After chlorinating: wait 12-24 hours for disinfection contact time, then flush all chlorine from system (1-4 hours typically). Continue using bottled water until you receive negative bacteria test results—this takes 1-2 weeks after disinfection. Never assume the well is safe based on chlorination alone; bacteria can survive if the contamination source isn't addressed or if chlorine didn't reach all areas.

⚠️ Immediate Safety

Do NOT drink the water until disinfected and tested
Do NOT turn on pump if electrical components were submerged
Use bottled water for drinking, cooking, brushing teeth, baby formula
Don't assume "clear water" is safe—bacteria are invisible

Flooding is one of the most serious threats to private well safety. Floodwater carries bacteria, viruses, parasites, chemicals, fuel, sewage, and countless other contaminants. Even brief flooding can introduce dangerous pathogens into your water supply.

Step 1: Assess the Situation

Before starting disinfection, evaluate the extent of damage:

Did floodwater reach the wellhead? Even touching the casing base means potential contamination
Was the wellhead submerged? Assume contamination entered the well
Is there visible damage? Cracked casing, displaced cap, damaged wiring
Is the pump running normally? Don't operate if electrical components were flooded
Is there debris/mud in water? May require professional flushing

Step 2: Initial Inspection

Before disinfecting, inspect the well system:

Check well cap and sanitary seal for damage
Look for debris around the wellhead
Inspect electrical connections (have electrician check if submerged)
Verify pressure tank and controls are operational
Clear any mud or debris from wellhead area

Step 3: Shock Chlorination Procedure

Materials Needed

Unscented household bleach (5-6% sodium hypochlorite) or well chlorination tablets
Clean bucket for mixing
Garden hose
Safety glasses and rubber gloves
Funnel (optional, for adding to well)

Chlorine Amount Calculator

Amount of bleach needed depends on well diameter and water depth. For common residential wells:

Well Diameter	Bleach per 100 ft water
4 inch	1 cup
6 inch	2 cups
8 inch	4 cups

Step-by-Step Process

Turn off power to pump
Remove well cap carefully
Mix bleach with water in bucket (dilutes for easier distribution)
Pour chlorine solution into well
Lower a garden hose into well, restore power, run pump to recirculate chlorinated water back into well for 15-20 minutes
Turn off pump, remove hose from well
Open each faucet in house (hot and cold) until you smell chlorine, then close
Replace well cap
Wait 12-24 hours—do not use any water
Flush system: Open outside spigot away from septic; run until chlorine smell is gone (may take several hours)
Flush inside fixtures until chlorine-free

⚠️ Important Warnings

Don't mix chlorine with other chemicals
Ventilate area when working with chlorine
Don't discharge chlorinated water into streams, ponds, or septic systems in large volumes
Highly chlorinated water can damage water treatment equipment—bypass during process

Step 4: Testing

After chlorine is flushed from system:

Wait 1-2 weeks before testing (allows bacteria to repopulate if contamination remains)
Test for bacteria (total coliform and E. coli)
If positive, repeat chlorination or call professional
If negative, water is safe to drink
Consider additional tests for nitrates and other contaminants after major flooding

When to Call a Professional

Seek Professional Help If:

Floodwater entered the well directly
Visible mud or debris in well or water
Pump or electrical system was submerged
Well remains contaminated after shock chlorination
Structural damage to wellhead or casing
You're not comfortable with the process
Well was submerged for extended period

Frequently Asked Questions

Is my well contaminated after a flood?

If floodwater reached your wellhead, assume contamination. Do not drink until disinfected and tested negative for bacteria.

How long should I wait to use well water after disinfection?

Wait 12-24 hours for disinfection, then flush chlorine. Continue using bottled water until bacteria test returns negative—1-2 weeks after disinfection.

Can I just let my well 'clear up' naturally?

No—pathogens can persist indefinitely. Proper disinfection and testing are required. Natural flushing doesn't eliminate bacteria.

Need Emergency Well Service?

Southern California Well Service provides emergency flood response, professional disinfection, and testing coordination.

Call (760) 463-0493

Related Guides

Bacteria in Well Water

Understanding bacterial contamination.

Preventing Contamination

Long-term protection strategies.

Well Disinfection After Flood