How Much Chlorine Bleach Should I add to a 8000 Gallon Storage Tank?

Q: I have discovered I have coliform bacteria in my holding  tank.  How much bleach should I add to an 8000 gallon tank if it is a 8.25% solution vs a 5% solution (clorox)?


A: For complete disinfection of water systems, it is recommended you apply 50 PPM of chlorine, and let it sit for 24 hours.  Measure the chlorine residuals after the 24 hours, and if there is less than 10 PPM, repeat the procedure.

You have to do a little bit of division to get the right amount for an 8,000 gallon tank, at about 5 quarts, or 1.25 gallons.  But that’s with 5% bleach (50,000 ppm concentration).  So if you’re working with 8.25% bleach instead (82,500 ppm concentration), then it changes to just over 3 quarts, or 0.75 gallons.  That should work for an 8000 gallon tank in order to kill bacteria if you let it sit 12 hours.

Please let us know if you need anything from us; normally this support feature is meant for customers needing technical support or advice on equipment to use that we would provide, so please let us know if there’s anything we can offer you for your water.

See our How To Guide on Disinfecting with Chlorine.

A few points that you might want to remember:

1. While shock chlorination corrects immediate bacteria and/or odor problems in wells and piping systems, it does not correct the source of the bacteria. If bacteria are entering the well from a septic tank or other source, the bacteria will become present again after the well has been sanitized.

2. Shock chlorinating your well may cause the water to turn a dark color and the chlorine may clean the well shaft and pipe of iron and sediment. The water may initially be very high in sludge and rust and cause damage to pipes and fixtures. It is best not to run water high in rust and sediment into water softeners, interior fixtures, water heaters etc.

3. Shock chlorination of wells or piping systems may loosen up scale, iron deposits and other materials, which can clog fixtures, appliances and valves in the piping system. Care should be taken when flushing the piping, and all aerators removed to prevent clogging. In some extreme cases of corroded piping, the piping may fail and start to leak after this procedure. Chlorination will not remove nitrate or other contaminants.