Also in: Disaster Response and Recovery
Well Shock-Chlorination Dose
The household bleach to shock-chlorinate a private well from the casing diameter and standing water column.
Example
You enter
- Casing inside diameter (in) 6
- Standing water column (ft) 100
- Target concentration (ppm) 100
- Bleach available chlorine (%) 6
You get
- Well water volume 147 gal
- Available (100%) chlorine 0.122 lb
- Bleach (gal) 0.245
Checked against published worked examples from: Montana DEQ.
Details, formula, and sources
ScopeWell volume, the available chlorine for the target ppm, and the bleach to pour in. The local health department governs the procedure and clearance.
Formula or tablewell_volume_gal = 0.0408 x casing_in^2 x column_ft; bleach_gal = volume x target_ppm / (1,000,000 x (bleach% / 100)); available_cl_lb = (volume / 1,000,000) x target_ppm x 8.34.
Source and editionAWWA A100 / state private-well shock-chlorination guidance (by name).
Free accessState and extension well-disinfection guides are public; bleach strength is on the label.
What governsEstimate. AHJ and licensed professional govern.
API field namescasing_diameter_in, water_column_ft, target_ppm, bleach_pct, well_volume_gal, available_cl_lb, bleach_gal
- Target concentration default 100 ppm; a shock is commonly about 50 to 200 ppm held overnight (often 12 to 24 hours)state well guidance
- Bleach strength plain unscented household bleach, about 5 to 8.25% available chlorine; ignores the slight bleach specific gravity, so round upproduct label
- Clearance pump to waste until the chlorine clears, then retest; the health department governs the bacteriological clearancestate well code