How to Get Rid of Chloroform in Water

Chloroform in drinking water is almost always a byproduct of the disinfection process itself, formed when chlorine reacts with naturally occurring organic matter in the source water. Removing it depends on whether you’re dealing with a household tap or an entire municipal supply, and the options range from something as simple as boiling to engineered systems like reverse osmosis membranes and packed-tower aeration. The wrinkle most people miss is that drinking is only part of the exposure: showering and bathing can deliver roughly as much chloroform into your body through your skin and lungs as swallowing the water does.

Why Chloroform Forms in Tap Water

Chloroform does not typically enter water from industrial pollution or a contaminated aquifer, though that can happen near waste sites. The far more common source is your local water utility. When a treatment plant adds chlorine to kill bacteria and viruses, that chlorine reacts with organic substances already dissolved in the water, producing a family of compounds called trihalomethanes. Chloroform is the most abundant of these.¹ The organic precursors come from decaying leaves, soil runoff, and algae in the source water. Research on Lake Zürich water, for instance, identified phenol-type compounds in natural organic matter as likely chloroform precursors, though other functional groups also contribute.²

This means chloroform levels in tap water fluctuate seasonally and geographically. In spring and fall, when runoff carries more organic material into reservoirs and rivers, chloroform formation tends to spike. Groundwater sources generally have less organic matter and produce lower levels than surface water, but they are not immune. Understanding that the chlorine-plus-organics reaction is the root cause matters because the most effective long-term strategies attack one side of that equation or the other: either remove the organic precursors before chlorination, or switch to a disinfectant that produces less chloroform in the first place.

Simple Household Removal Methods

If you’re looking for something you can do today without buying specialized equipment, boiling is the most accessible option. Chloroform is volatile, meaning it evaporates from water more readily than water itself, especially at high temperatures. Research on chlorinated and chloraminated tap water found that boiling reduced trihalomethane concentrations by roughly 64 to 98 percent, depending on the type of disinfection and how long the water boiled.³ There is a catch, though. In chlorinated water (as opposed to chloraminated water), a one-minute boil reduced chloroform by only about 34 percent because new chloroform was still forming from the residual chlorine reacting with organics even as existing chloroform was escaping into the air. In chloraminated water, a one-minute boil cut chloroform by about 75 percent, since chloramines are less reactive in generating new trihalomethanes at those temperatures. To get the best results from boiling chlorinated water, you need to keep it at a rolling boil for several minutes in an open pot, preferably in a well-ventilated kitchen so you’re not just breathing the chloroform you’ve driven off.

For everyday convenience, a carbon filter is the most popular household choice, but not all carbon filters are equally effective against chloroform. Activated carbon adsorbs chloroform onto its surface, and performance depends heavily on the carbon’s pore structure. Research on specialized carbonaceous adsorbents found that chloroform removal improved with higher surface area in the microporous range, but that larger pore sizes actually hurt performance.⁴ Among commercially available materials, activated carbon fibers outperformed standard granular activated carbon for chloroform adsorption in some comparisons.⁵ Meanwhile, simple sand-replacement filter beds using granular activated carbon have been found to function poorly for removing trihalomethanes and other volatile organics.⁶

What does that mean for the pitcher filter sitting on your counter? Pitcher filters, faucet-mounted units, and under-sink carbon block systems vary enormously. The ones that have been tested and certified to NSF/ANSI Standard 53 for volatile organic compound removal are much more likely to deliver real results than a generic carbon cartridge. Activated carbon block filters, which compress the carbon into a solid block rather than loose granules, must pass specific performance assessments to meet that certification.⁷ If a product doesn’t explicitly claim NSF 53 certification for trihalomethanes or volatile organics, treat its chloroform-removal claims with skepticism. And regardless of the filter type, carbon eventually becomes saturated and stops adsorbing new contaminants. Replacing cartridges on schedule is not optional if you’re relying on the filter for chloroform reduction.

Reverse Osmosis and Membrane Filtration

For a more thorough household solution, reverse osmosis units represent the high end of point-of-use treatment. These systems force water through a semipermeable membrane under pressure, and the right membrane can reject the vast majority of dissolved contaminants. Pilot-plant testing of composite RO membranes showed that one high-performance membrane achieved better than 99.5 percent rejection of trihalomethanes in both tap water and brackish water, though a different membrane type reached only about 80 percent retention.⁸ The takeaway is that membrane quality matters. Not every RO unit will strip chloroform equally well, so look for systems tested specifically against volatile organics. RO systems also waste water and can be slow, producing treated water at a trickle into a storage tank. They are best suited for drinking and cooking water rather than whole-house treatment.

Why Showering Matters as Much as Drinking

Most people think of water contamination as a drinking problem. Chloroform exposure doesn’t work that way. Research measuring chloroform in people’s exhaled breath found that every route of exposure from daily water use contributed meaningfully: ingestion, inhalation, and skin absorption.⁹ A study specifically designed to separate inhalation from skin absorption during showers found that the internal dose from dermal exposure was roughly equal to the dose from inhalation alone. Breath concentrations after a normal shower ranged from about 6 to 21 micrograms per cubic meter, compared to about 2.4 to 10 micrograms per cubic meter for inhalation-only exposure, and the difference was highly statistically significant.¹⁰

Modeling work estimated that the amount of chloroform absorbed through the skin during a 10-minute shower falls in the range of 0.25 to 0.66 milligrams per milligram-per-liter of tap water concentration.¹¹ What that means in practical terms is that a kitchen faucet filter or a pitcher won’t solve the problem on its own. If you’re concerned enough about chloroform to filter your drinking water, it’s worth considering your shower and bath exposure too. Risk assessments have estimated that the risk from a single 10-minute shower can be in the same ballpark as the risk from drinking a couple of liters of tap water per day.¹² Showerhead filters with activated carbon exist, though their capacity is limited by high flow rates and warm water, which makes adsorption less efficient. A whole-house carbon filter installed at the water main is the more reliable option for tackling both drinking and bathing exposure simultaneously.

How Water Utilities Tackle Chloroform at the Source

The most effective way to reduce chloroform in tap water is to prevent it from forming in the first place. Utilities do this primarily through two strategies: removing organic precursors before adding chlorine, and switching to disinfectants that produce fewer trihalomethanes.

Enhanced Coagulation and Pre-Treatment

Enhanced coagulation uses higher doses or more effective coagulants to pull dissolved organic matter out of the water before disinfection. A study comparing titanium, aluminum, and iron-based coagulants found that titanium chloride outperformed the other two for controlling chloroform formation potential, largely because it was better at removing aromatic organic compounds, which are particularly reactive with chlorine.¹³ Combining pre-oxidation steps with conventional coagulation, sedimentation, and filtration pushes performance further. Research found that micro-ozone pre-treatment followed by coagulation-sedimentation-filtration and then ozone-activated-carbon polishing was the most effective sequence for reducing chloroform precursors.¹⁴

Analyses of different treatment approaches have shown that enhanced coagulation, granular activated carbon adsorption, and membrane filtration all reduce the cancer risks associated with trihalomethanes, with the benefit increasing in waters with higher bromide levels.¹⁵ Filtration of raw water through granular activated carbon or strong-base ion-exchange resins, sometimes combined with coagulation, also changes the rate at which chloroform forms when the water is later disinfected.¹⁶

Switching Disinfectants

The other major lever is replacing free chlorine with chloramines, which are formed by combining chlorine with ammonia. Chloramination dramatically reduces chloroform output. One study found that chloramination produced, on average, 10 times less chloroform than free chlorine.¹⁷ Another measured a 75 to 87 percent reduction in chloroform formation when pre-formed monochloramine was used in place of chlorine.¹⁸ However, chloramination is not a free lunch. It tends to increase the formation of certain other byproducts, including some nitrogen-containing compounds that carry their own health concerns. Utilities that switch to chloramines trade one set of byproducts for a different, generally smaller set, and they need to manage the chemistry carefully.

Aeration and Air Stripping

Because chloroform is volatile, you can remove it by increasing the contact between water and air, encouraging it to transfer from the liquid phase to the gas phase. At the household scale, this is essentially what happens when you boil water with the lid off. At the utility or industrial scale, the same principle is engineered into packed-tower air strippers. These are tall columns filled with packing material that creates a large surface area. Water trickles down through the packing while air is blown upward, and volatile compounds like chloroform transfer into the airstream and are vented away. Design procedures for these towers account for water and air temperature, the volatility of the target contaminant, and the type of packing material.¹⁹

Air stripping works well for chloroform because the compound has a reasonably high Henry’s law constant, meaning it prefers to move from water into air at low concentrations. The tradeoff is that you need to manage the off-gas, since you’re essentially moving the chloroform from water into air. In some regulatory settings, the exhaust air has to be treated with a vapor-phase carbon adsorber before release. For a homeowner, a simpler version of aeration might mean using a spray aerator on your faucet or simply letting water sit in an open container for a period, though neither approach is as efficient as a designed packed tower.

Advanced Oxidation and Chemical Reduction

When conventional treatment is not enough, advanced oxidation processes can break chloroform down chemically rather than just moving or trapping it. The UV/hydrogen peroxide process generates hydroxyl radicals, which are among the most reactive oxidants known. Researchers measured rate constants for the reaction of hydroxyl radicals with 37 different halogenated disinfection byproducts, including trihalomethanes, and found that the reactivity spanned four orders of magnitude.²⁰ Chloroform, being a relatively stable small molecule, sits at the lower end of that reactivity range. That means UV/peroxide systems can degrade it, but you may need higher doses or longer contact times compared to some other byproducts.

On the chemical reduction side, zerovalent iron has been studied for decades as a way to break down chlorinated compounds in groundwater. The problem is that chloroform is one of the most stubborn targets. Even with nano-sized particles, bimetallic formulations, and sulfidated versions of zerovalent iron, transformation of chloroform tends to be slow.²¹ Recent work on simultaneously sulfidated and nitridated iron, prepared through mechanochemical ball milling, showed improved performance, but this remains a research-stage approach. When nanoscale zerovalent iron is combined with activated carbon as a support material, the system can degrade trihalomethanes, though chloroform is the last to go compared to the brominated species.²² None of these chemical reduction methods are available as consumer products; they exist in the realm of contaminated-site remediation and experimental treatment trains.

Bioremediation for Contaminated Groundwater

At sites where chloroform has contaminated the subsurface, whether from industrial spills or landfill leachate, biological treatment is another option. Certain microbes can break down chloroform, though they rarely use it as a direct food source. Instead, the process is usually cometabolic: bacteria growing on a primary substrate like butane, methane, propane, toluene, or ammonia produce enzymes that happen to also attack chloroform on the side.²³ Under anaerobic conditions, methane-producing microbes are the most commonly reported chloroform degraders, though some sulfate-reducing and fermenting bacteria can also contribute.

Field-relevant research in soil and groundwater microcosms showed that butane-utilizing bacteria could degrade chloroform aerobically, and that adding these organisms to the soil (bioaugmentation) shortened the time before degradation started. Temperature mattered enormously: at 15°C, no chloroform breakdown was observed after weeks, while warmer conditions allowed activity to begin within days.²⁴ The practical limitation of bioremediation is that chloroform itself can inhibit the very bacteria you’re counting on to degrade it, particularly at higher concentrations. It is a viable strategy for low-level groundwater contamination at moderate-to-warm temperatures, but it requires patience and monitoring that a homeowner is unlikely to manage. It’s used primarily by environmental engineers cleaning up contaminated aquifers.

Choosing the Right Approach for Your Situation

The best removal strategy depends on whether your concern is routine tap water with typical disinfection byproduct levels or a specific contamination event. For everyday municipal water, the hierarchy roughly shakes out like this:

Drinking water only: An under-sink activated carbon block filter certified to NSF 53 for volatile organic compounds handles most people’s needs. Reverse osmosis adds a second layer of protection if levels are high.
Drinking plus bathing: A whole-house granular activated carbon system installed at the point of entry addresses all taps, showers, and baths at once. These systems require periodic media replacement and flow-rate monitoring.
Boiling as a stopgap: Effective for chloroform reduction, but only if you boil for several minutes with the lid off and ventilate the kitchen. A one-minute boil may not remove much from chlorinated water.
Letting water sit: Leaving a jug of water uncovered for several hours allows some chloroform to off-gas, but the process is slow and incomplete at room temperature.

For well water contaminated by a spill or industrial source, the calculus changes. You’re likely dealing with higher concentrations than typical disinfection byproducts, and the contamination may include other chlorinated solvents. In that case, professional testing and a tailored treatment system are warranted. Packed-tower aeration, advanced carbon adsorption, and possibly even in-situ bioremediation of the aquifer itself may come into play, all of which require engineering input rather than a trip to the hardware store.

Getting Your Water Tested

Before investing in treatment, it helps to know what you’re actually dealing with. Chloroform in water is measured using gas chromatography, often with an electron capture detector, which is sensitive enough to pick up trace-level concentrations.²⁵ Your local water utility is required to test for total trihalomethanes and publish results in annual consumer confidence reports. These reports tell you the average and peak trihalomethane levels at the plant, though concentrations at your tap may be higher because chloroform continues to form as water travels through the distribution system. If you want your own measurement, state-certified testing labs can analyze a water sample for trihalomethanes, typically for a modest fee. Collect the sample after the water has been sitting in your pipes for a few hours, such as first thing in the morning, to get a realistic picture of what you and your household are actually exposed to.

It is worth keeping in mind that the U.S. Environmental Protection Agency limits total trihalomethanes in municipal water to 80 parts per billion. Chloroform usually makes up the majority of that total. Most municipal systems stay well below the limit, but older distribution networks, warm seasons, and source water with heavy organic loading can push levels up. If your water report shows total trihalomethanes consistently above 60 or 70 parts per billion, an activated carbon or whole-house treatment system is a reasonable investment. If levels are in the low teens or single digits, a kitchen pitcher filter may be all you need, or you may decide the risk is small enough not to worry about at all.