The Portland Water Bureau disinfects water from the Bull Run Watershed to ensure your water is safe to drink. Below you will find commonly asked questions about this process.
How is Portland’s drinking water disinfected?
The treatment process begins with chlorine, the primary disinfectant used to protect the public against waterborne bacteria and viruses. Ammonia is then added to combine with the chlorine to create a long lasting disinfectant: chloramine.
Chloramine is a type of oxidant that is formed when chlorine and ammonia combine. Chloramine has been used since the early 1900’s, and Portland has been using chloramine as a secondary disinfectant since 1957. Chloramines prevent harmful bacteria from re-growing in our water system.
Why is drinking water disinfected?
Before disinfectants were commonly used to treat drinking water, many people died or became ill from contaminated water. Disinfection dramatically minimizes water borne illness and is one of the greatest public health advances of the 20th century.
Is chlorine safe to consume?
The level of chlorine in your drinking water is safe to consume. The Portland Water Bureau is required to meet strict drinking water standards which are regulated by the Environmental Protection Agency (EPA) and Oregon Health Authority. The use of chlorine is one of the most common and cost effective methods to protect public health from waterborne diseases. The EPA allows up to 4 parts per million (4 milligrams/liter) of chlorine in drinking water. The chlorine levels in Portland’s system are below this standard.
Some people are more sensitive to chlorine than others. Individuals with health concerns should consult with their health practitioner to learn more. Some customers choose to use filters to remove taste and odor.
The Portland Water Bureau reports use of chloramine in our annual Drinking Water Quality Report, under Disinfectant Residual as the total chlorine residual (table on pages 5 and 6).
Does chlorine affect the taste and smell of my water?
Some customers can detect chlorine in drinking water while others do not. Chlorinated water can taste and smell differently than untreated water and water from other sources. Some people like the taste and smell of chlorinated water, while others choose to use filters that remove chlorine taste and odors.
How much chlorine is added to our water, and does that amount change?
Adjusting the amount of chlorine that is used for disinfection is based on precise water quality sampling data that is collected throughout our distribution system. Chlorine levels are carefully controlled and can change seasonally. The amount that is added is between 2.2 mg/L (fall and winter) and 2.5 mg/L (spring and summer).
While chlorine residual is one of the most essential components of public drinking water treatment, it can be influenced by other water quality parameters including pH and temperature. Understanding these interactions is critical to providing clean and safe drinking water, which is why chlorine levels are routinely tested and closely monitored.
What are the benefits of using chloramination?
Because chlorine breaks down more quickly than chloramines, using chloramines allows the Portland Water Bureau to add lower levels of chlorine for disinfection while maintaining an effective disinfectant level throughout the system. Additionally, the use of chloramines compared to chlorine produces fewer regulated disinfection byproducts (DBPs), including trihalomethanes (THM) and haloacetic acids (HAA).
My water tastes more chlorinated than usual; what’s going on?
It may one of a few different reasons for observing a change in taste:
1) Seasonal Change
Colder water during the fall and winter can hold more dissolved gases, including chlorine, which will escape when you open your faucet. Also, microbial organisms are less active in colder conditions, resulting in a slower decline in chlorine levels.
2) Personal Sensitivity
Some customers’ palettes are more sensitive than others.
The Portland Water Bureau may have flushed fire hydrants in your neighborhood, and you may be noticing a slightly higher level of chlorine. We manually flush fire hydrants as a part of maintaining high quality drinking water, and flushing brings in fresh water with slightly higher chlorine levels. The amount of chlorine you detect is safe to drink.
4) Adjustment to Different Water
Some customers that travel out of town and return to Portland may also notice a difference in taste if they temporarily get used to a different water source.
A change in taste and smell are common side effects from some medications. Some medications can taste bitter or contribute to dry mouth which may influence how drinking water tastes. Be sure to consult with your physician if you are concerned with the side effects.
Does the Portland Water Bureau add additional chlorine in the distribution system?
We do not add additional chlorine boosters in the distribution system. Instead, chloramines serve as a long-acting and stable disinfectant used to deliver safe drinking water as it travels through over 2,200 miles of pipe. The Portland Water Bureau, along with many other drinking water systems in the country, has been using chloramines as a disinfectant for public health since 1957.
What if I am sensitive to chlorine or chloramines? How can I reduce my exposure?
While from a public health perspective it is not necessary to remove chloramines, some people are more sensitive to chlorine than others. Individuals with health concerns, including skin sensitivities to chloramines, should consult with their health practitioner to learn more.
Some customers choose to use filters to remove chlorine taste and odor from their drinking water and shower. The Portland Water Bureau recommends NSF/ANSI Standard 42 certified filters for reducing chloramines for consumption.
The NSF/ANSI Standard 177 is for showerheads that reduce free chlorine. Since Portland uses chloramine (chlorine + ammonia) and not free chlorine, filters with the NSF/ANSI 177 standard may not work effectively. Some certified granular activated carbon showerheads claim to reduce chloramine. Customers may have success with vitamin C showerhead filters, but these are not certified.
An inexpensive option to dechlorinate water for drinking purposes includes adding dissolvable vitamin C tablets, acidic fruit (e.g. orange, lemon, lime), or sliced cucumber to a pitcher of water. The vitamin C or ascorbic acid neutralizes chloramines, and according to the Center for Disease Control, “reduces the disinfectant to tasteless and colorless form of chloride.”
What should I do if I receive dialysis treatment?
Dialysis requires a large amount of water to clean a patient’s blood. Dialysis centers remove all chemical disinfectants including chlorine and chloramines. Consult with your health care professional if you have specific questions. For customers with dialysis systems inside their home, contact the Portland Water Bureau Water Line at 503-823-7525 to sign up for notifications when chlorine levels are adjusted.
Will chloramines affect my pets or aquatic animals?
Chloramines and ammonia must be removed for indoor or outdoor fish, reptiles, shellfish, and amphibians. Safe treatment products including granular activated charcoal filtration systems, dechlorinator products, and water conditioner additives are available at aquarium supply stores. Hobbyists should always follow product instructions.
Will chloramines affect plants or gardens?
According to the Center for Disease Control, “Plants are not harmed by water treated with chloramine.” Some customers, however, use dechlorinator tablets to remove chloramines before applying water to plants or making compost teas.