How to shock chlorinate a private water well in Texas
Summarized from Texas A&M AgriLife Extension publication ESC-059, How to Disinfect a Water Well Through Shock Chlorination (Texas Well Owner Network). General information, not professional advice. If you are unsure about your well, call a licensed water well contractor.
When to disinfect a well
Wells can become contaminated by flood water, by a septic system that is not working properly, or by livestock grazing near the well. AgriLife also recommends shock chlorination when a water system is contaminated with bacteria, which can happen when a well is installed, when the pump or plumbing is repaired, or when rainfall runoff gets into the well. (AgriLife: Shock Chlorination of Wells)
If your well flooded, the Texas Well Owner Network says to assume the water is contaminated until it has been tested. Until then, do not use it for drinking, cooking, making ice, bathing, or washing clothes or dishes. Use bottled water, water boiled for one minute, or water from a source you know is safe.
Check this first: submersible pumps only
This method is for private wells with a properly functioning submersible pump only (a pump that sits down in the well, under the water). It will not work for a jet pump or a damaged system. A drop in water pressure when the pump turns on can be a sign of damage. In those cases, contact a contractor.
What you need
- A wrench to open the well
- A garden hose that reaches from an outdoor faucet to the well
- Protective goggles and gloves
- A clean 5 gallon bucket and a funnel
- 5 gallons of uncontaminated water, such as bottled water
- Unscented household liquid bleach less than 6 months old
How much bleach to use
Find the water depth in your well by subtracting the static water level (the distance from the ground to the water) from the total well depth. If you do not know the static water level, use the total well depth. Then match that depth with your well diameter.
| Water depth (feet) | 4 inch | 6 inch | 8 inch | 24 inch | 36 inch |
|---|---|---|---|---|---|
| 10 | 6 cups | 7 cups | 8 cups | 20 cups | 2.5 gal |
| 20 | 7 cups | 8 cups | 10 cups | 2.5 gal | 4.5 gal |
| 50 | 8 cups | 10 cups | 14 cups | 5 gal | 10.5 gal |
| 100 | 10 cups | 16 cups | 22 cups | not listed | not listed |
| 150 | 12 cups | 20 cups | 30 cups | not listed | not listed |
| 200 | 14 cups | 1.5 gal | 2.5 gal | not listed | not listed |
| 400 | 22 cups | 2.5 gal | 4.5 gal | not listed | not listed |
16 cups equals 1 gallon. AgriLife warns that too much chlorine can be harmful, so follow the chart carefully. Source: ESC-059, Table 1.
Step by step
- Flush the well. Clear debris from around the well and check it for damage. If the water has been cloudy or muddy, run a hose from the outdoor faucet nearest the well until the water is clear.
- Power off. Turn off the pump's circuit breaker. Put water softeners and household filters in bypass or "out of service" mode.
- Open the well. Remove the threaded plug on a well seal, or unbolt and lift a well cap or sanitary cap. If your well does not look like any of these, call a contractor.
- Mix the bleach. Fill the bucket about three quarters full with bottled water, add the amount of bleach from the chart, and pour it through the funnel into the well without splashing.
- Recirculate. Turn the breaker back on, connect a hose to the outdoor faucet nearest the well, put the hose into the well (through the funnel for a well seal), and let it run for 30 minutes.
- Run it through every faucet. Starting outside and working in, open each tap one at a time, hot and cold, toilets, showers and tubs, until you smell bleach, then close it. Leave the chlorinated water in the plumbing for at least 8 hours or overnight.
- Flush. Run an outdoor hose until you no longer smell chlorine, then run each indoor fixture until the smell is gone.
- Reconnect and retest. Disinfect the softener or filters following the manufacturer's instructions, reconnect them, and send a water sample to a lab. Do not drink the water until it has been tested.
Protect your septic system while flushing
Keep the flushed water away from your septic system, landscaping, ponds and streams. AgriLife's older guide explains why: a large load of chlorine in the septic tank can kill the beneficial bacteria, and the system may then need to be re-inoculated. Let the hose drain to a field or low area away from plants you care about. If you have an aerobic system, see our aerobic septic maintenance rules.
Retest, and what if bacteria come back
Before drinking, cooking, making ice or preparing food, have the water tested by a certified laboratory. If bacteria are still present, repeat the chlorination and test again. If contamination shows up a third time, look for a source of reinfection, and the well may need to be cleaned or repaired by a contractor. If the groundwater itself is the source, AgriLife says you will need continuous disinfection rather than repeated shock treatments.
Find a lab near you on our East Texas well water testing labs page, or read the well water testing guide. You can also search the TCEQ certified laboratory database.