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The temporary change takes place annually and usually occurs for about a month each year from the end of February through early April. It is done before the summer hotter temperatures which can increase the potential for bacterial growth in pipes.
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North Texas Municipal Water District (NTMWD) first disinfects water using ozone and chlorine as part of the treatment process to eliminate bacteria and viruses. Then, for most of the year, NTMWD also adds chloramine (chlorine plus ammonia) as a secondary disinfectant to keep drinking water clean as it travels from the treatment plants through miles of pipes to homes and businesses. Each spring for one month, NTMWD temporarily suspends the use of ammonia and uses free chlorine as the secondary disinfectant to maintain water quality year-round. This process is also commonly referred to as annual chlorine maintenance. Check out this ’Protecting Water Quality’ fact sheet (PDF) from NTMWD for detail information.
This change is a common water system maintenance practice among water providers in states with warmer climates. North Texas Municipal Water District (NTMWD) uses it to maintain the system and ensure high water quality year-round. It’s important to do this before summer because hotter temperatures can increase the potential for bacterial growth in pipes. Learn more about why public water systems may make a temporary change in disinfectant from the Texas Commission on Environmental Quality (TCEQ).
Yes, chlorine is tested, and many other compounds in water are monitored continuously. North Texas Municipal Water District (NTMWD) conducts a quarter-million tests each year in a state-certified laboratory to monitor, regulate, and report water quality. In some cases, NTMWD is voluntarily increasing the frequency of testing above what is required. During the disinfectant change in 2018, the Texas Commission on Environmental Quality (TCEQ) also collected 117 samples from 31 public water systems that deliver NTMWD water to confirm compliance.
While the levels of chlorine in the water during the temporary disinfectant change are consistent with levels found in the water throughout the year, the temporary suspension of ammonia can make the chlorine more noticeable. Outdoor temperatures and overall water use also influence the reaction of chlorine to other materials in the water supply. This may cause smell and taste to fluctuate year to year. The intensity of the chlorine taste and smell can depend on the distance you are from the water treatment plant. North Texas Municipal Water District (NTMWD) does not increase the amount of chlorine in the water during its four-week change in disinfectant; its taste and smell are more pronounced due to the absence of the ammonia (PDF).
Not everyone notices a change in the water during this period. The closer you live to the water treatment plant, the more noticeable the chlorine odor or taste may be. However, those who are sensitive to the changes can reduce chlorine taste and the odor by following these tips:
If looking to use a filter of some kind, recommend using a National Science Foundation (NSF/ANSI) approved water filter.
Local water providers (cities or utility districts) who receive North Texas Municipal Water District (NTMWD) water may help move the chlorine-disinfected water through the system faster by flushing water out of fire hydrants. Frequent flushing helps maintain the system, ensure high water quality, and reduce the chlorine odor and taste. Performing system flushing in the spring also helps save valuable water during the summer months.