Temporary Disinfectant Conversion from Chloramine to Free Chlorine

[Slaphppy7]

The following was posted to Facebook (which I finally joined, not long ago), for a town near me. My town occasionally "flushes" the water system, so I assume they do it the same way, and for the same reasons. But, I did not know that free chlorine was used during the process...anyhow, thought it was a bit interesting, and good to know for fishkeepers in towns that do this. I'm assuming the "extreme weather conditions" highlighted below refers to the recent summer-long drought we experienced.

The City of Port Neches public water system, (PWS) ID 1230010, will temporarily convert the disinfectant used in the distribution system from chloramine to free chlorine. The conversion will begin on 1/13/2024 and continue through 1/17/2024. During this period, you may experience taste and odor changes associated with this type of temporary disinfectant conversion.
Public water systems are required to properly disinfect their water and maintain an adequate disinfectant residual in the distribution system. Chloramine, free chlorine combined with ammonia, is widely used as a disinfectant because it persists for long periods while also limiting the formation of disinfection by-product contaminants. Prolonged use of chloramine coupled with other factors that can affect water quality, such as high temperatures or stagnation of water, may result in the growth and/or persistence of organic matter within the pipes of the distribution system, which may hinder the ability to maintain an adequate disinfectant residual. A temporary conversion to free chlorine, partnered with flushing activities, helps to rid distribution pipes of this organic matter and improve the quality of your water overall.
City of Port Neches has chosen to implement a temporary disinfectant conversion to free chlorine based on the following:
__Due to the extreme weather conditions and the unusual demand for water.
Please share this information with all people who drink this water, especially those who may not have received this notice directly (i.e., people in apartments, nursing homes, schools, and businesses). You can do this by posting this notice in a public place or distributing copies by hand or mail.

 

[Uberhoust]

Our community changes up the treatment during yearly flushing processes as well. When they do a flush in our community, they quadruple the free chlorine added, and it is noticeable just with the odor of the water coming out of the tap. For us it occurs in the middle of spring just after the spring run off. Also the amount of chlorine is increased based on the sediment load in the water, the higher the sediment the more chlorine is added, we don't get any notification of this. I believe this is a common process for most public water supplies.

 

[GaryE]

Where I am now, we get notice. In my previous city, we got a week's warning, as apparently someone tried suing because some sediment stained their laundry...

The flush used there wasn't just free chlorine though, as we didn't have chloramines. It wasn't unsafe to drink, but it could kill a tank. I check by running water into a clear cup before I start water changes. Pipe flush water is greyish.

Here's it's a May and November problem.

 

[Uberhoust]

I knew of a fellow who raised South American catfish of various types in Victoria BC who had an automated water change system that effectively aged the water as part of a continuous process. A rockslide occurred at Sooke reservoir, one of the water supplies for Victoria, the city engineers upped the chlorine heavily and he ended up losing a large number of his fish.
The variability of the concentration of disinfectants in our water supply is one of the reasons I am not overly concerned about the precision of measuring the chlorine treatment, I just make sure it is within 10% deviation from the recommended amount.