OWASA has resumed the disinfection of drinking water with a compound of chlorine and ammonia called chloramines.

In March, OWASA used only chlorine, which is a somewhat more intense disinfectant than chloramines, in accord with a State requirement. The purpose of the State’s requirement for chlorine disinfection one month per year is to help ensure that harmful bacteria do not grow in pipes that carry drinking water to homes, businesses, schools, etc. OWASA has over 400 miles of water mains.

Chlorine disinfection resulted in chlorine taste and odor in drinking water in March and early April.

Background information about water disinfection with chlorine and chloramines 

To remove chlorine taste and odor from OWASA water in March and early April, customers can:

  • Filter the water with activated carbon. Water pitchers with activated carbon filters are sold locally.
  • Let water sit for a day or so. (We suggest keeping the water in an open container stored in a refrigerator.)
  • Boil the water for one minute to evaporate the chlorine.
  • Add a few lemon slices to a pitcher of water.  The lemon has ascorbic acid, which neutralizes the chlorine. 

Before 2002, OWASA used chlorine in the form of sodium hypochlorite (bleach) for disinfection. 

In January, 2002, OWASA began using chloramines to disinfect drinking water. Disinfection with chloramines has improved the taste and odor and the overall quality of drinking water.

The change to chloramine disinfection in 2002 has reduced the levels of disinfection byproducts which may be harmful at high levels over a lifetime. The disinfection byproducts result from the chemical reaction of chlorine with organic material, and they are called trihalomethanes (THMs) and haloacetic acids (HAAs). Small particles of organic material are naturally present in the water from lakes.

According to the U.S. Environmental Protection Agency and the N.C. Department of Environment and Natural Resources’ Public Water Supply Section, a person would have to drink 2 liters of water with elevated THM/HAA levels every day for a lifetime to have a one-in-a-million chance of having cancer or certain other health effects.

OWASA’s water is safe to drink when disinfected with either chlorine or chloramines. OWASA carefully controls chlorine and chloramines in the water to comply State and Federal drinking water standards, which limit chlorine and chloramines to four parts per million. One part per million is like a penny in $10,000.

Chlorine and chloramines are toxic to fish and amphibians because these species absorb chlorine/chloramines through their gills (which also absorb oxygen). When OWASA releases water from fire hydrants, OWASA uses special equipment and a chemical to neutralize the chlorine or chloramines so they will not harm fish if the water reaches a stream or creek.

However, chlorine and chloramines are not absorbed into the blood stream when they pass though the intestines of people and other mammals such as pets.

When OWASA water is used for dialysis, which involves contact between blood and water, the dialysis facility uses carbon filers to remove chlorine or chloramines.

Some people may have allergies or sensitivity to chlorine and/or chloramines. Special carbon filters can be used to remove chlorine and chloramines from drinking water. Some bottled water does and some does not contain chlorine or chloramines. It is necessary to check the contents label and/or contact the supplier for specific information. 

Drinking water disinfected with chlorine or chloramines can over time deteriorate the rubber compounds in toilet flappers and washers in faucets and other water fixtures.  OWASA suggests getting advice from a plumber or company that sells plumbing supplies about choosing a toilet flapper and washers. Some are made with a material that is intended to be resistant to chlorine and chloramines. (OWASA does not evaluate or recommend particular brands.)

OWASA is strongly committed to protecting the public health and safety. Although chloramines and chlorine can affect toilet flappers, etc. OWASA believes that the public health is the most important consideration in treating water to control bacteria and minimize disinfection byproducts.

In the Triangle region, water utilities including OWASA, the City of Raleigh and the Town of Cary use chloramines for disinfection except for one month of the year (March or a similar period).

For more information, please contact:

  • Rachel Monschein, Laboratory Supervisor at the Jones Ferry Road Water Treatment Plant, 919-537-4227 or
  • Ken Loflin, Water Supply and Treatment Manager, 919-537-4232;