Water treatment · Wells
Well shock chlorination bleach amount.
Pick the casing diameter and the depth of water, and get the bleach amount from the Oregon State table.
Inputs
Result
Enter your numbers.
How Much Bleach to Shock a Well: how it works
Oregon State University's Well Water Program recommends an initial chlorine concentration of 50 to 100 ppm and gives a table of ordinary liquid laundry bleach (5 to 6% sodium hypochlorite, no additives or scents) by well diameter and depth of water; the amounts are "very roughly 100 ppm". You dilute the bleach, pour it into the well, circulate it through the whole plumbing system until you smell chlorine at every fixture, wait 6 to 12 hours, then flush and retest the water after 2 to 3 days.
Worked example. A 6 inch well with 75 feet of water falls in the 50 to 100 foot column: 4 cups (1 quart, about 0.95 L). Dilute it at 2 cups or less per 2 gallon bucket, so 2 buckets. A 4 inch well with the same 75 feet of water needs 2 cups.
Depth bands. The table uses four depth columns: under 50 feet, 50 to 100, 100 to 150, and 150 or more. A depth exactly on a boundary goes into the higher column. Do not remove well cap bolts if pipes stick up from the cap: OSU warns the pump may be resting on the cap. If in doubt, call a well or pump professional.
Frequently asked questions
How much bleach do I need to shock a well?
It depends on diameter and depth of water. A 6 inch well with 50 to 100 feet of water takes 4 cups of ordinary bleach per the Oregon State table.
What bleach should I use?
Plain liquid laundry bleach labelled sodium hypochlorite at about 5 to 6%, without additives or scents.
How long do I wait after shocking a well?
Wait 6 to 12 hours for the chlorine to work, flush the chlorinated water from the well and pipes, and retest the water after 2 to 3 days.
Why should I dilute the bleach first?
OSU says to use 2 cups or less per 2 gallon bucket, because straight chlorine can corrode metal well parts.
Sources
Checked
Runs entirely in your browser. Nothing you type is sent or stored.
Not professional advice
Do not drink or cook with the water during the 6 to 12 hour hold, or afterwards, until a lab coliform test comes back clean (OSU). Do not put the chlorinated flush water on plants. Amounts are a rough starting point from a university table for ordinary drilled wells. Dug wells, large storage tanks and treatment equipment differ. Chlorine solution is hazardous. Follow your local health authority and call a well professional if unsure. Not professional advice.