Water main installation in process (C) Daniel Friedman Chloramine Secondary Disinfectant Treatment in Drinking Water
Tests for chloramine in water

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This article explains the use of chloramines, a secondary disinfectant used to treat drinking water.

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Chloramine Treatment of Drinking Water

Photo of slime formation inside of a garden hose (C) Daniel FriedmanThis series of articles explains many common water contamination tests for bacteria and other contaminants in water samples. We describe what to do about contaminated water, listing common corrective measures when water test results are unsatisfactory.

We include water testing and water correction measures warnings for home owners and especially for home buyers when certain conditions are encountered, with advice about what to do when these circumstances are encountered.

Chloramine disinfectants are used to treat drinking water because of the ability of these chemicals to provide longer-lasting disinfection of drinking water as it moves through water mains and piping between the community water source and the end-using water consumer.

Our photo (left) shows common slime formation inside of a garden hose. Similar slime layers may form inside of water pipes where water is not treated for its prevention.

U.S. EPA Information on Chloramines in Drinking Water

Chloramines in Drinking Water used as disinfectants: ammonia + chlorine

Chloramines are disinfectants used to treat drinking water. Chloramines are most commonly formed when ammonia is added to chlorine to treat drinking water. The typical purpose of chloramines is to provide longer-lasting water treatment as the water moves through pipes to consumers.

This type of disinfection is known as secondary disinfection. Chloramines have been used by water utilities for almost 90 years, and their use is closely regulated. More than one in five Americans uses drinking water treated with chloramines. Water that contains chloramines and meets EPA regulatory standards is safe to use for drinking, cooking, bathing and other household uses.

Many utilities use chlorine as their secondary disinfectant; however, in recent years, some of them changed their secondary disinfectant to chloramines to meet disinfection byproduct regulations. In order to address questions that have been raised by consumers about this switch, EPA scientists and experts have answered 29 of the most frequently asked questions about chloramines. We have also worked with a risk communication expert to help us organize complex information and make it easier for us to express current knowledge.

The question and answer format takes a step-wise approach to communicate complex information to a wide variety of consumers who may have different educational backgrounds or interest in this topic. Each question is answered by three key responses, which are written at an approximately sixth grade reading level. In turn, each key response is supported by three more detailed pieces of information, which are written at an approximately 12th grade reading level. More complex information is provided in the

Additional Supporting Information section, which includes links to documents and resources that provide additional technical information.

EPA continues to research drinking water disinfectants and expects to periodically evaluate and possibly update the questions and answers about chloramines when new information becomes available.

The Environmental Protection Agency regulates the safe use of chloramines in drinking water.3

  • EPA requires water utilities to meet strict health standards when using chloramines to treat water.
  • EPA chloramines regulations are based on the average concentration of chloramines found in a water system over time.
  • EPA regulates certain chemicals formed when chloramines react with natural organic matter4 in water.

Additional Supporting Information Concerning the Use of Chloramines in Drinking Water

  1. Dichloramine is formed when the chlorine to ammonia-nitrogen weight ratio is greater than 5:1, however, this reaction is very slow. Organic chloramines are formed when chlorine reacts with organic nitrogen compounds. Source: Optimizing Chloramine Treatment, 2nd Edition, AwwaRF, 2004
  2. Trichloramine formation does not usually occur under normal drinking water treatment conditions. However, if the pH is lowered below 4.4 or the chlorine to ammonia-nitrogen weight ratio becomes greater than 7.6:1, then trichloramine can form. Trichloramine formation can occur at a pH between 7 and 8 if the chlorine to ammonia-nitrogen weight ratio is increased to 15:1. Source: Optimizing Chloramine Treatment, 2nd Edition, AwwaRF, 2004
  3. The drinking water standard for chloramines is 4 parts per million (ppm) measured as an annual average. More information on water utility use of chloramines is available at http://www.epa.gov/safewater/disinfection/index.html and in the 1997-1998 Information Collection Rule, a national survey of large drinking water utilities for the Stage 2 Disinfection Byproducts Rule (DBPR).

    Information on the Stage 2 DBPR is available at http://www.epa.gov/safewater/disinfection/stage2/.
    More information on EPA’s standard setting process may be found at: http://www.epa.gov/OGWDW/standard/setting.html.
  4. Natural Organic Matter: Complex organic compounds that are formed from decomposing plant, animal and microbial material in soil and water. They can react with disinfectants to form disinfection by products. Total organic carbon (TOC) is often measured as an indicator of natural organic matter.

-- Chloramines in Drinking Water, U.S. Environmental Protection Agency

Public Concerns Regarding Use of Chloramines

Quoting from Drinking Water Issues: Chloramine, U.S. Environmental Protection Agency:

Recently San Francisco Public Utility Commision (SFPUC - http://www.sfwater.org )changed from using free chlorine to chloramine in its drinking water transmission pipes. Some people are concerned for possible public health implications and for reported effects on fish and amphibians.

Using chloramine to disinfect drinking water is a common standard practice among drinking water utilities. A number of utilities have made this switch from chlorine to chloramines to enhance water safety and compliance with drinking water health standards. For example, the East Bay Municipal Utility District (EBMUD - http://www.ebmud.com/), which serves drinking water to customers in parts of the greater San Francisco Bay area, switched from chlorine to using chloramine in February, 1998.

Background information on chloramines

Chlorine has been safely used for more than 100 years for disinfection of drinking water to protect public health from diseases which are caused by bacteria, viruses and other disease causing organisms. Chloramines, the monochloramine form in particular, have also been used as a disinfectant since the 1930's.

Chloramines are produced by combining chlorine and ammonia. While obviously toxic at high levels, neither pose health concerns to humans at the levels used for drinking water disinfection.

Chloramines are weaker disinfectants than chlorine, but are more stable, thus extending disinfectant benefits throughout a water utility's distribution system. They are not used as the primary disinfectant for your water. Chloramines are used for maintaining a disinfectant residual in the distribution system so that disinfected drinking water is kept safe. Chloramine can also provide the following benefits:

  • Since chloramines are not as reactive as chlorine with organic material in water, they produce substantially lower concentrations of disinfection byproducts in the distribution system. Some disinfection byproducts, such as the trihalomethanes (THMs) and haloacetic acids (HAAs), may have adverse health effects at high levels. These disinfection byproducts are closely regulated by EPA. EPA recently reduced the allowable Maximum Contaminant Levels for total THMs to 80 ug/L and now limit HAAs to 60 ug/L.

    The use of chlorine and chloramines is also regulated by the EPA. We have Maximum Residual Disinfectant Levels of 4.0 mg/L for both these disinfectants. However, our concern is not from their toxicity, but to assure adequate control of the disinfection byproducts.
  • Because the chloramine residual is more stable and longer lasting than free chlorine, it provides better protection against bacterial regrowth in systems with large storage tanks and dead-end water mains.
  • Chloramine, like chlorine, is effective in controlling biofilm, which is a slime coating in the pipe caused by bacteria. Controlling biofilms also tends to reduce coliform bacteria concentrations and biofilm-induced corrosion of pipes.
  • Because chloramine does not tend to react with organic compounds, many systems will experience less incidence of taste and odor complaints when using chloramine.

Other concerns with chloramines in drinking water

Chloramines, like chlorine, are toxic to fish and amphibians at levels used for drinking water. Unlike chlorine, chloramines do not rapidly dissipate on standing. Neither do they dissipate by boiling. Fish owners must neutralize or remove chloramines from water used in aquariums or ponds.

Treatment products are readily available at aquarium supply stores. Chloramines react with certain types of rubber hoses and gaskets, such as those on washing machines and hot water heaters. Black or greasy particles may appear as these materials degrade. Replacement materials are commonly available at hardware and plumber supply stores.

- Source: Drinking Water Issues: Chloramine, U.S. Environmental Protection Agency,

Thanks to reader Frank A. Marshall, AIA, LEED AP, at SMB&R, an Architecture, Structural Engineering, Interior Design firm in Camp Hill, PA for suggesting the addition of Chloramine drinking water treatment information

Basic water purification procedures that can be used in an emergency areat DRINKING WATER - EMERGENCY PURIFICATION. If community or private wells are back in operating and providing water, do not assume that the water is sanitary and ok to drink until responsible authorities have said so.

Even then, local water pipes in a building may be unsanitary and additional cleaning or disinfection may be needed.

See WELL CHLORINATION SHOCKING PROCEDURE and See WATER TESTS, CONTAMINANTS, TREATMENT for advice on using a private well for drinking water.

Tests for Chloramine in Water

Chloramine testing is provided by a variety of laboratories, including companies who provide tests used by aquarium enthusiasts (chloramine at sufficient concentration and depending on the pH of the water, can injure fish).

Before becoming too worried, note that as with any chemical, "the dose makes the poison", and we undestand that Chloramine-T is under study as a treatment to kill bacteria and parasites in koi fish ponds.

Sources for Kits or Equipment for Chloramine Tests in Water

Because chloramine remains stable for a longer period in water, and because (sticking around longer) that may permit chlorine molecules to bond with other materials, different tests may be appropriate. A test kit that you intend to use to screen water for chlorine should include a test for "total chlorine" not just "free chlorine" because of this binding problem.

  • Aquarium suppliers sell chlorine test kits that can detect chloramine in water.
  • Chlorine/Chloramine Test Kits produced by Ecological Laboratories are sold through Amazon and at other outlets.
    [Disclosure: Amazon pays us a pittance for readers who buy from the above links]
  • Here are two additional Chloramine Test Kits sold at Amazon, but you should check online fdor a supplier and price that you like.
    [Disclosure: Amazon pays us a pittance for readers who buy from the above links]
  • Local water testing labs in your area may also offer these tests as they are quite simple to perform.

Prices for these tests typically run from under $8.00 to $15.00.

Chlorine in water is tested for as hypochlorite (Cl2O2) (bleach solution). We discuss chlorine testing at CHLORINE TESTS, WATER, where we detail our procedure to test well water for trace levels of chlorine.


Also see DRINKING WATER EMERGENCY PURIFICATION for a discussion of various methods used to purify emergency drinking water.

Chloramine Disinfectant Water Treatment Effectiveness & Chloramine in Drinking Water Research

  • Also see citations at REFERENCES
  • Brodtmann Jr, Noel V., and Peter J. Russo. "The use of chloramine for reduction of trihalomethanes and disinfection of drinking water." Journal (American Water Works Association) (1979): 40-42.
  • Glaze, William H. "Drinking-water treatment with ozone." Environmental science & technology 21, no. 3 (1987): 224-230.
  • Kim, B. R., J. E. Anderson, S. A. Mueller, W. A. Gaines, and A. M. Kendall. "Literature review—efficacy of various disinfectants against< i> Legionella</i> in water systems." Water Research 36, no. 18 (2002): 4433-4444.
  • LeChevallier, Mark W., Nancy J. Welch, and Darrell B. Smith. "Full-scale studies of factors related to coliform regrowth in drinking water." Applied and Environmental Microbiology 62, no. 7 (1996): 2201-2211.
  • Regan, John M., Gregory W. Harrington, and Daniel R. Noguera. "Ammonia-and nitrite-oxidizing bacterial communities in a pilot-scale chloraminated drinking water distribution system." Applied and Environmental Microbiology 68, no. 1 (2002): 73-81.
  • Reynolds, Kelly A., Kristina D. Mena, and Charles P. Gerba. "Risk of waterborne illness via drinking water in the United States." In Reviews of environmental contamination and toxicology, pp. 117-158. Springer New York, 2008.
  • Richardson, Susan D., Michael J. Plewa, Elizabeth D. Wagner, Rita Schoeny, and David M. DeMarini. "Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: a review and roadmap for research." Mutation Research/Reviews in Mutation Research 636, no. 1 (2007): 178-242.
  • Richardson, S. D., A. D. Thruston Jr, T. V. Caughran, P. H. Chen, T. W. Collette, K. M. Schenck, B. W. Lykins Jr, Ch Rav-Acha, and V. Glezer. "Identification of new drinking water disinfection by-products from ozone, chlorine dioxide, chloramine, and chlorine." In Environmental Challenges, pp. 95-102. Springer Netherlands, 2000.
  • Stewart, Mic H., Roy L. Wolfe, and Edward G. Means. "Assessment of the bacteriological activity associated with granular activated carbon treatment of drinking water." Applied and environmental microbiology 56, no. 12 (1990): 3822-382



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