Enter your tank size, or your well casing and water depth, and get the exact amount of bleach or dry chlorine to add.
Units
A tank's rated size is what it holds full. What matters is the water actually in it.
Shock chlorination makes the water unusable until the chlorine has been flushed out completely.
Gallons.
Feet, measured across the widest point.
Feet, from the water surface down to the bottom — not the tank's full height.
Feet.
Feet.
Feet, from the water surface down to the bottom.
Inside diameter of the casing. Most drilled residential wells are 4 or 6 inch.
Feet from the standing water level down to the bottom — not the total well depth. Your well driller's report has both.
Use 50 ppm after repairs, a new pump or tank, or plumbing work. Use 100 ppm when coliform is found, for a new well, or after flooding. Going higher is rarely useful and makes the flush longer. Shock chlorination is a one-time treatment, not a routine one — city tap water carries just a few ppm at most.
What are you using?
Use NSF/potable-grade calcium hypochlorite. Do not use pool Tri-Chlor tablets or stabilized pool chlorine.
Check the bottle before you measure. Household bleach is no longer a single strength — it now runs from about 6% to 8.25% sodium hypochlorite, and the percentage is printed on the label. Use fresh, plain, unscented liquid bleach. Avoid scented, splashless, color-safe and gel bleach, which contain thickeners and additives that do not belong in drinking water.
Add this much liquid chlorine
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What to do with it
Before you start. Bypass the softener, filters and any other treatment equipment. Wear goggles and gloves, and keep the area ventilated — chlorine fumes in an enclosed well house or tank can be dangerous. Never pour chlorinated water into a septic system, onto plants, or into a creek or pond.