How to Test for Chloramine in Tap Water (The Free vs Total Trick)
Water Testing Guide
How to Test for Chloramine in Tap Water (The Free vs Total Trick)
Chloramine is invisible to the free-chlorine strip most people reach for, which is why so many homeowners test their water, see a low number, and still smell a swimming pool. Here is how to detect chloramine at home with a simple two-number comparison, when a lab test earns its money, and why the answer decides which carbon filter actually works in your house.
TL;DR
Chloramine is chlorine bonded to ammonia, and utilities that use it serve more than one in five Americans according to the EPA. A single test strip cannot identify it. The reliable home method is a comparison: measure free chlorine and total chlorine on the same water, then subtract. If total is meaningfully higher than free, the gap is chloramine. The even easier method is asking your utility or checking your Consumer Confidence Report, which names the disinfectant outright. If you want a certified answer plus the rest of the city-water picture, the $199 City Water Test Kit measures free chlorine, total chlorine, and chloramine in one lab panel.
- Chloramine = total chlorine minus free chlorine. The gap between the two numbers is the diagnostic
- EPA legal ceiling (MRDL): 4.0 mg/L for chloramine, the same as chlorine, per 40 CFR 141.65
- Free-chlorine strips read near zero on chloraminated water. That false negative is the most common testing mistake we see
- Chloramine requires catalytic carbon. Standard GAC removes it poorly and needs far more contact time
- At normal tap levels this is a taste and filter-sizing question, not an emergency. The exceptions are fish tanks and home dialysis, where chloramine must be removed completely
Aidan Walsh, Mid Atlantic Water: "Half the chloramine calls I get start the same way: the customer already tested, the strip said almost nothing was there, and the water still tastes like a pool. The strip was not lying, it just answered a different question. Free-chlorine strips are blind to chloramine. You need two numbers, free and total, and the difference between them tells you what your utility is really sending you. Get that one fact right and the carbon filter decision makes itself."
What This Guide Covers
- What Chloramine Is and Why Utilities Use It
- Does My Water Have Chloramine? Start Here
- The Free vs Total Method: How the Math Works
- Three Ways to Test for Chloramine
- Chloramine Detector: Enter Your Two Readings
- Why Chloramine Changes the Filtration Answer
- Fish Tanks, Dialysis, and Rubber Parts
- 4 Common Chloramine Testing Mistakes
- Frequently Asked Questions
What Chloramine Is and Why Utilities Use It
Chloramine is what you get when a utility adds a small, controlled amount of ammonia to chlorinated water. The chlorine and ammonia bond into monochloramine, a disinfectant that has been used in American water systems since the 1930s. According to the EPA, more than one in five Americans drink water treated with chloramine. By system count it is less common (2019 EPA data puts it at roughly 17 percent of disinfecting public water systems), but the systems that use it tend to be big-city systems, which is why the population share is so much larger. Washington DC, San Francisco, Denver, Dallas, Boston, and Philadelphia all chloraminate.
Utilities do not switch to chloramine to save money or cut corners. They switch for two engineering reasons:
- Stability. Free chlorine decays as water travels through miles of distribution pipe, which means the far ends of a large system can run short on disinfectant. Chloramine holds its residual for weeks instead of days, so it protects the whole system evenly.
- Fewer regulated byproducts. Free chlorine reacts with natural organic matter in the water to form trihalomethanes and haloacetic acids, which the EPA limits because of long-term health concerns. Chloramine forms far less of them, and many systems adopted it specifically to comply with the EPA's disinfection byproduct rules.
Like chlorine, chloramine is regulated under a Maximum Residual Disinfectant Level of 4.0 mg/L measured as an annual average (40 CFR 141.65). Typical taps run well below that, usually in the 1 to 3 ppm range. At those levels, chloramine in your drinking water is legal, considered safe by the EPA and CDC, and, for most households, a taste and filtration question rather than a health problem. The three genuine exceptions (fish, dialysis, and certain rubber parts) get their own section below.
Does My Water Have Chloramine? Start Here
Before you buy any test, know that this question has a free, definitive answer: your utility will tell you. Chloramination is a deliberate, documented treatment choice, not a contaminant that sneaks in. Two ways to get it:
- Read your Consumer Confidence Report. Every community water system publishes one annually, and the disinfectant is named outright, usually as "chloramine" or "monochloramine" on the disinfectant residual line. Our guide to reading your water quality report shows exactly where to look.
- Call the utility. The number is on your water bill. Ask "do you use chlorine or chloramine as your secondary disinfectant?" and you will have your answer in under a minute. Ask also whether they do an annual free-chlorine conversion (a temporary switch, often called a chlorine burn), because that affects when you test.
So why test at all? Two reasons. First, the CCR describes the system, not your tap: if you are verifying that a carbon filter is removing chloramine, only a measurement at your own faucet answers that. Second, some utilities blend sources or switch disinfectants seasonally, and a test tells you what is in the water today. There are also softer clues worth knowing:
The Free vs Total Method: How the Math Works
Here is the part that trips people up, and it is also the entire trick. Chlorine tests come in two flavors. A free chlorine test measures disinfectant that is unbonded and active (hypochlorous acid and hypochlorite). A total chlorine test measures everything chlorine-based in the water, both free chlorine and chlorine that has bonded to ammonia. Chloramine registers on total but not on free. So no single reading identifies it; the comparison does:
Reading the result is straightforward:
- Total 1.0, free 0.9: nearly all free chlorine. Your utility chlorinates. Standard carbon handles it.
- Total 1.2, free 0.1: the 1.1 ppm gap is chloramine. Your utility chloraminates, and your carbon needs to be catalytic.
- Total and free both near zero: either a filter upstream is doing its job, or the water sat in your plumbing long enough to lose its residual. Run the tap 60 seconds and retest.
In practice you run the comparison with a DPD kit (the pink-color drop or tablet chemistry utilities themselves use in the field): DPD #1 reagent gives you free chlorine, adding DPD #3 to the same sample gives you total. Two strip products (one free-range, one total-range) work too, just less precisely. The step-by-step sampling technique (run the cold tap first, read within the time window, test fresh water) is identical to a chlorine test, and our companion guide on how to test for chlorine in tap water walks through it in detail, so we will not repeat it here.
Why "Combined Chlorine" Means Chloramine
Chemists call the total-minus-free gap "combined chlorine," meaning chlorine bonded to ammonia or organic material. In a swimming pool, combined chlorine is a waste product. In city tap water, it is almost entirely monochloramine that the utility created on purpose by dosing ammonia at the plant (typically around a 5:1 chlorine-to-ammonia ratio). Same chemistry, opposite intent.
Three Ways to Test for Chloramine
Ranked from cheapest to most complete. Note that the first two answer "which disinfectant do I have and roughly how much," which is all most homeowners need. The lab earns its cost when you want a certified number plus everything else in city water at the same time.
Two-Strip Comparison
- One bottle of free-chlorine strips, one of total-chlorine strips
- Dip both in the same fresh sample, subtract
- Good enough to identify which disinfectant you have
- Buy low-range drinking water strips, not pool strips
DPD Kit or Digital Meter
- DPD #1 reads free; DPD #3 added after reads total
- The same field chemistry utilities use
- Digital colorimeters remove the color-matching guesswork
- Best repeatable option for monitoring a filter
Certified Lab Panel
- Free chlorine, total chlorine, and chloramine reported separately
- Plus lead, copper, disinfection byproducts, and 40+ other city-water contaminants
- Our $199 City Water Test Kit, expert review by Aidan included
- The right call before sizing a whole-house system
An honest note on timing: chloramine is best measured on fresh water at the tap because disinfectant residuals start changing the moment the sample leaves the faucet. Good mail-in panels (ours included) handle this with field-test components and preserved bottles, but if your only question is "chlorine or chloramine," the $20 two-strip comparison at your own sink answers it today. The lab panel is for when you are about to spend real money on a whole-house system and want the full picture: chloramine level, the disinfection byproducts it left behind, and the lead and copper your own plumbing may be adding. You can compare all our water test kits here, see the best tap water test kit comparison, or start from the city pillar guide, how to test your tap water. On a private well none of this applies (wells are not chloraminated); see city water testing vs well water testing for which world you are in.
Chloramine Detector
Enter your free and total chlorine readings from the same water sample. We will do the subtraction and tell you what it means.
Why Chloramine Changes the Filtration Answer
If the test says chloramine, the practical consequence is simple but expensive to get wrong: the carbon filter that works on chlorine will underperform on chloramine. Standard granular activated carbon (GAC) destroys free chlorine almost on contact, which is why a modest GAC tank can dechlorinate a whole house for years. Chloramine is a much more stable molecule. Plain GAC removes it slowly and needs far more contact time than a typical tank provides, so a GAC system installed on chloraminated water either lets chloramine slip through from day one or exhausts in a fraction of its rated life.
The fix is catalytic carbon: activated carbon whose surface has been modified to accelerate the chemical breakdown of chloramine into harmless chloride and nitrogen compounds. Same tank format, same maintenance-free operation, different media inside, and the sizing math is more conservative because chloramine needs longer contact with the media. This is exactly why we ask "chlorine or chloramine?" before quoting any city-water carbon system, and why the free-vs-total test (or one lab panel) is worth running before the purchase, not after.
| Behavior | Free Chlorine | Chloramine |
|---|---|---|
| Residual life in pipes | Days; decays across the system | Weeks; holds to the far ends of the system |
| Boiling / letting water sit | Gasses off in hours to overnight | Barely budges; not a practical removal method |
| Standard GAC carbon | Excellent, long media life | Poor; needs far more contact time than normal tanks provide |
| Catalytic carbon | Excellent | Designed for it; the correct media choice |
| Shows on a free-chlorine strip | Yes | No; reads at or near zero |
| Shows on a total-chlorine test | Yes | Yes, lumped into the total |
Browse the whole-house carbon filter collection for backwashing catalytic systems, or the non-backwashing carbon systems if you want a unit with no drain, no electricity, and no moving parts. If you are not sure which media your water calls for, tell Aidan your utility's name or send your free/total readings to 800-460-5810 and he will spec it in a couple of minutes.
Fish Tanks, Dialysis, and Rubber Parts
For drinking and bathing, chloramine at normal residual levels is a comfort question. Three situations are different, and they are worth naming plainly because they are the cases where "roughly zero" is not good enough:
Aquariums and ponds
Chloramine is toxic to fish at tap-water concentrations. It crosses gill membranes and binds hemoglobin directly, and unlike free chlorine it does not gas off if you let the water sit for a day, so the old fill-a-bucket-and-wait trick fails completely. Water conditioners that only neutralize chlorine make it worse: they break the chlorine-ammonia bond and leave the ammonia behind in the tank. If you keep fish on chloraminated water, use a conditioner rated for chloramine, and test with a total-chlorine method, not a free strip.
Home dialysis
Chloramine in water used for hemodialysis can cause hemolytic anemia because the dialysis membrane puts water in near-direct contact with the bloodstream. Dialysis providers know this and specify carbon pretreatment with strict contact-time requirements and routine testing. If anyone in your home dialyzes, do not improvise: follow your provider's water spec exactly and tell them your utility chloraminates.
Rubber and elastomer parts
Chloramine degrades certain rubber compounds faster than chlorine does, especially natural rubber and some older elastomers used in toilet flappers, faucet washers, supply-line gaskets, and water-heater components. If you have replaced the same flapper twice in three years on city water, chloramine is a plausible suspect. Chloramine-resistant parts exist (look for materials rated for chloraminated water), and a whole-house catalytic carbon system removes the cause at the point of entry.
The Annual "Chlorine Burn" Can Confuse Your Test
Many chloraminated systems temporarily switch to free chlorine for a few weeks each year (often in spring) to deep-clean the distribution pipes. During the burn, your free reading jumps, the pool smell gets stronger, and a test run that week will tell you the system is chlorinated when it usually is not. If your readings seem to contradict the CCR, ask the utility whether a conversion is running, and retest a few weeks later.
4 Common Chloramine Testing Mistakes
1. Trusting a single free-chlorine strip
The classic false negative. Free-chlorine strips are blind to chloramine, so a chloraminated tap reads near zero while still smelling like a pool. Any time a low strip reading disagrees with your nose, run a total-chlorine test before concluding anything.
2. Subtracting readings from two different samples
The free-vs-total math only works if both numbers come from the same water. Residuals change as water sits, so a free reading from this morning minus a total reading from tonight produces a meaningless gap. Draw one fresh sample and run both tests within a minute or two.
3. Testing during the annual free-chlorine conversion
If your utility runs a spring chlorine burn, a test that week shows a chlorinated system even though you get chloramine the other eleven months. Check the CCR or ask the utility, and if a conversion is running, retest after it ends before making a filter decision.
4. Buying carbon before identifying the disinfectant
This is the expensive one. A standard GAC system bought for "chlorine taste" on chloraminated water disappoints from the first month and exhausts early. The $20 two-strip comparison, a call to your utility, or one lab panel before the purchase prevents it entirely.
Frequently Asked Questions
How can I tell if my water has chloramine?
Two reliable routes. Easiest: check your utility's annual Consumer Confidence Report or call the utility; chloramination is a documented treatment choice and they will name the disinfectant outright. At your own tap: measure free chlorine and total chlorine on the same fresh sample (a DPD kit with both reagents, or one free-range strip plus one total-range strip). If total is meaningfully higher than free, the difference is chloramine.
What test kit detects chloramine?
Any kit that measures both free and total chlorine can detect chloramine by subtraction: total minus free equals combined chlorine, which in city water is almost entirely chloramine. DPD drop and tablet kits ($15-50) do this with two reagents, digital colorimeters do it with less guesswork, and a certified lab panel like the $199 City Water Test Kit reports free chlorine, total chlorine, and chloramine separately alongside lead, copper, and disinfection byproducts. A single "chlorine" strip by itself cannot identify chloramine.
What is the difference between chlorine and chloramine?
Chlorine (free chlorine) is the traditional drinking water disinfectant. Chloramine is chlorine deliberately bonded to ammonia (monochloramine), used by utilities because it stays active far longer in distribution pipes and forms fewer regulated disinfection byproducts. Practically, chloramine does not gas off when water sits, survives boiling, is blind to free-chlorine test strips, and requires catalytic carbon rather than standard GAC to remove.
Is chloramine in tap water safe to drink?
At regulated levels, yes. The EPA sets a Maximum Residual Disinfectant Level of 4.0 mg/L for chloramine, the same ceiling as chlorine, and states that water containing chloramine within that limit is safe for drinking, cooking, and bathing. More than one in five Americans drink chloraminated water, some cities for many decades. The exceptions are indirect: chloramine is toxic to fish, must be removed from water used for kidney dialysis, and can shorten the life of certain rubber plumbing parts.
How do I remove chloramine from my water?
Catalytic activated carbon is the standard whole-house answer. Chloramine is far more stable than free chlorine, so ordinary GAC carbon removes it poorly and needs much more contact time than a typical tank provides. A catalytic carbon system sized with adequate contact time breaks chloramine down into harmless chloride at the point of entry, covering every tap and shower. Reverse osmosis systems with carbon prefilters handle it at a single faucet.
Does boiling or letting water sit remove chloramine?
Not in any practical timeframe. Free chlorine gasses off an open pitcher overnight and boils off in minutes, but chloramine is stable by design: that stability is exactly why utilities use it. Boiling chloraminated water for the many hours it would take is not realistic, and letting it stand barely changes the level. If you need chloramine gone, filtration through catalytic carbon (or a chloramine-rated conditioner, for aquariums) is the answer.
Why is chloramine dangerous for fish but not for people?
Route of exposure. When people drink chloraminated water, digestion neutralizes it before it reaches the bloodstream. Fish take water across their gill membranes, where chloramine enters the blood directly and binds hemoglobin. Dialysis is the human parallel: the dialysis membrane puts water in near-direct contact with blood, which is why dialysis water must have chloramine removed completely and why providers specify carbon pretreatment and routine testing.
How long does chloramine last in water?
Weeks. Monochloramine holds a usable residual for far longer than free chlorine, which typically decays within days in distribution pipes. That persistence is the main reason large systems use it: the residual survives to the far ends of long distribution networks. It is also why the sit-overnight and boiling tricks that work on chlorine fail on chloramine, and why an aquarium bucket left out for a day is still not fish-safe.
Not sure whether your carbon filter should be catalytic? Tell Aidan your utility's name, or send him your free and total chlorine readings, and he will tell you which system fits in a couple of minutes. Email support@midatlanticwater.net or call Aidan directly at 800-460-5810. No obligation, no hard sell, no charge for the recommendation.
Written by Aidan Walsh, owner of Mid Atlantic Water. 32+ years installing water treatment systems across Pennsylvania, Maryland, Delaware, New Jersey, Virginia, and beyond. Article reviewed July 2026.