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How to sanitize a well

We'll shock chlorinate the well to kill bacteria and fix contamination.

How-to · Home plumbing
24–48 hours (including wait and flush time)
What you'll need
  • Unscented household bleach (5.25–6% sodium hypochlorite)
  • Garden hose
  • Water test kit or lab test (for bacteria after flushing)

At a glance

  • Use unscented household bleach—about 1 quart per 100 feet of water in the well for a typical 6-inch well.
  • Pour the bleach into the well and run the hose back into the well to circulate for 30 minutes.
  • Run water through every faucet until you smell chlorine, then let it sit for 12–24 hours.
  • Flush the system until chlorine is gone—test with a kit or wait until you cannot smell it.
  • Do not drink the water until the chlorine is flushed and you have retested for bacteria.
Quick triage — pick your path

Get started

Choose the option that matches what you see. You can jump straight to that section.

Steps

Goal: Shock chlorinate the well and restore safe water.

  • Calculate the bleach amount. Bypass softeners and filters. Pour bleach into the well.
  • Good: Bleach is in the well. Proceed to Circulate.
  • Bad: Cannot access the well—call a well driller or pump installer.

Circulate

Goal: Mix chlorine through the well water.

  • Run a hose from a faucet back into the well. Circulate for 30 minutes.
  • Good: Chlorine is mixed. Proceed to Run through fixtures.
  • Bad: No outdoor faucet—use the closest faucet and circulate as best you can.

Run through fixtures

Goal: Get chlorine to every part of the system.

  • Run each faucet until you smell chlorine. Let sit 12–24 hours.
  • Good: Chlorine is throughout the system. Proceed to Flush.
  • Bad: No chlorine smell at a fixture—check that the bypass is correct and water is flowing.

Flush

Goal: Remove chlorine from the system.

  • Run each faucet until you no longer smell chlorine. Start outdoors.
  • Good: No chlorine smell. Proceed to Retest.
  • Bad: Chlorine persists—continue flushing; it can take several hours.

Retest

Goal: Confirm the water is safe for drinking.

  • Wait 24–48 hours. Have the water tested for coliform bacteria.
  • Good: Negative test. Water is safe. Proceed to Verification.
  • Bad: Positive test—repeat shock chlorination or call a well professional.

When to get help

Call a well professional if:

  • You cannot access the well or are unsure of the procedure.
  • The bacteria test stays positive after shock chlorination.
  • The well has a persistent contamination issue (may need structural repair or a new well).

Verification

  • No chlorine smell in the water.
  • Bacteria test is negative.
  • Water is safe for drinking, cooking, and bathing.

Reviewed by Blackbox Atlas

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