The Portland Water Bureau treats drinking water through a process called chloramination.
First chlorine is added to disinfect the source water to ensure that your water is protected from harmful bacteria and microorganisms. Then ammonia is added to ensure the disinfection remains stable throughout the entire distribution system. Portland has been using chloramines successfully for over 50 years, and adds an amount to maintain an effective level of disinfection throughout the distribution system, no more.
The ratio of chlorine to ammonia is approximately 4.9 to 1 by weight, with treatment levels ranging seasonally between 2.2 and 2.5 parts per million. To maintain an effective disinfectant in the system during the warmer months of the year, the concentration may be adjusted. This is to account for seasonally warm water temperatures that may cause chlorine residuals to decrease more rapidly, much like an evaporation process.
Some customers can be sensitive to changes in chlorine levels and will notice the fluctuations more than others. These changes do not signal a significant change in chlorine in the system, but is more likely due to work on the system or a change in outside temperatures, indicating that the chlorine is dissipating more quickly in a certain area. These changes in the chlorine taste and odor generally pass on their own after a few hours, and are not cause for alarm. Even though these changes may be detected, the chlorine level is still well within the accepted range.
Chlorine odor can be minimized by:
- Putting a pitcher of water in the refrigerator overnight to allow some of the chlorine to dissipate.
- Adding a slice of citrus or cucumber to the water to dechlorinate the water in a few hours.
- Boiling water and making coffee or tea to reduce chlorine by approximately 30%
- Putting plain water on a soft boil for 20 minutes
- A Vitamin C tablet of 1000 mg may be crushed and added to bath water
In humans, chlorine is neutralized through the digestive system, however fish are particularly susceptible to changes in chlorine and ammonia levels, as they absorb these elements into their bloodstream directly through their gills. Chlorine and ammonia can be counteracted in fish tanks by using a special filtering system, or using an additive or conditioner to remove them. Fish owners should check with their pet or aquarium store for these products.
For those with sensitivities, other alternatives to minimize chlorine can include the installation of activated carbon based faucet and shower filters. For recommendations on filters, contact NSF, a non-profit organization that tests and certifies drinking water filtration products, online or at 1-800-673-6275.
The Water Line is available 8:30 am – 4:30 pm Monday through Friday at 503-823-7525 or WBWaterLine@portlandoregon.gov. To learn more about home water quality, visit the Water Bureau’s Drinking Water Quality at Home page.