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

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Chloramine water disinfection:

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

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.

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Chloramine Treatment of Drinking Water

Photo of slime formation inside of a garden hose (C) Daniel Friedman

This 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.

Our photo (above) 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.

[Click to enlarge any image]

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

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 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
    More information on EPA’s standard setting process may be found at:
  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 - )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 -, 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:

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 for CONTAMINANTS 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.

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.

Reader Comment: home inspector concerned with chloramine-treated water

Independent House Diagnosis said:

HomeInspectors may wish to consider informing new end-users of houses receiving chloraminated water. Possible human and building effects are discussed at website of CCAC. For those who would call that inforamtion anecdotal I refer you to the book POISON SPRING , written by a 25 year EPA veteran. EPA is as behind on most issues as the entire world "health" community was on tobacco and asbestos and for similar reasons. - 2015/12/28


Thanks for the book suggestion, HI. Below I've added links to find at both Valliantos' Poison Spring as well as Rachel Carson's famous Silent Spring in the Chloramine references above.

Chloramine Disinfectant Water Treatment Effectiveness & Chloramine in Drinking Water Research


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