Brown Water after Shocking the Well

 Brownish or dirty looking water can be caused by many things. Practically always after you shock-chlorinate your well the water turns brown. The chlorine used to shock the well reacts with iron, manganese and reducing bacteria in the well and it is pulled into the water chlorine solution. That is the brown you see. Flushing the well by running the hoses for at least 12 hours or upto several day will clear up the problem. Don't panic, it is completely normal. Though the other major causes of brownish or dirty water are:

1. Surface infiltration or other contamination 
2. Well collapsing or water level dropping 
3. Iron (and/or manganese) in the water
4. Iron Bacteria
5. Earthquakes
6. Rust or breakdown of the metals in in the well or house 

What you are seeing is the gunk that had accumulated in your well. During well disinfection, free chlorine is introduced into the well water; there is no one standard for how much chlorine and methods to accomplish this disinfection so what your experience is will vary, but adequate amounts of chlorine will flush the mineral build up, iron in solution in the water and reducing bacteria out of the well.  Based on a survey of emergency disinfection protocols performed by Dr. Kelsey J. Pieper et. al and published earlier this year “Improving state-level emergency well disinfection strategies in the United States”,the scientists found that there were many differences in the protocols for  chlorine disinfection. 

Most protocols recommended that high chlorine doses be introduced into the well, circulated throughout the system, and stagnated for several hours up to 24 hours. The scientists point out that it is important that residual chlorine be measured because if too much of the chlorine solution reacts with iron or organic substances present in the well the effectiveness for disinfection is reduced. This is key because when iron or iron bacteria or other reducing bacteria react with chlorine (are oxidized) and are flushed out of the well into the water. If there is enough chlorine, the well will shed brown water, and be disinfected. 

Chlorination properly done can not only disinfect, but also rehabilitate the well. As a water well ages, the rate at which water can be pumped (commonly referred to as the well yield) tends to fall. This can be caused by:

• Incrustation from mineral deposits (including iron and manganese) or 
• Bio-fouling by iron bacteria 

The most common methods to rehabilitate a private water well are: acids or chlorine to dissolve the encrusting materials and bacterial slime from the well. This produces the brown water observed in a newly chorine shocked well. The chlorination  dissolves the encrustations and slime build up. These days regularly treating a well with chlorine is the recommended strategy to extend the life of a well and equipment and can improve the taste of the water. See well maintenance tips from Penn State University Extension or Alberta Provencal Government.

When I recently replaced my pump and pressure tank, I used a heck of a lot of chlorine in the powder form (a couple of cups or more of high-test calcium hypochlorite) to sanitize the well. Unfortunately, I was not able to mix the chlorine adequately. Mixing the chlorine  is accomplished by recirculating the water for a couple of hours. The result was that after running the hoses for about 12 hours the water appeared clear, but still had a measurable but low levels of chlorine. So, I need to keep diluting the chlorine solution by pumping the well to rid my well of it. Pockets of discolored water kept appearing for several days. Though I cannot run my well dry-it recharges faster than I can pump, I only ran the hoses only about 6-12 hours a day whenever a pop of rust colored water appeared.  It would still be almost 5 days before all trace of the chlorine was flushed from the system, and the water remained consistently clear,  but we were good with filtered water for coffee until then.

This was the longest it has ever taken to flush all the gunk out of the well which I attribute to not mixing the chlorine adequately. My husband, was briefly worried that I had somehow ruined the well or water supply because it seemed to go on and on. No worries, by the next week the water was clear and tasty. It takes patience to clear a well.