The reliable way to remove chlorine from water is activated carbon, which adsorbs it as water passes through. Letting water stand or boiling it also works to a degree, and ascorbic acid neutralizes it chemically. Which of those you should use depends on whether you need a glass, a bath, or the whole house, and on whether your utility uses chlorine or chloramine.
Carbon filtration, the everyday answer
Activated carbon removes chlorine efficiently and is the basis of almost every filter sold for taste and odor: pitchers, faucet mounts, countertop units, under-sink cartridges, refrigerator filters and whole-house tanks are all doing the same thing at different scales. Two variables decide how well it performs. Contact time is the first, which is why a large slow cartridge outperforms a small fast one and why whole-house units are physically big. Capacity is the second: carbon fills up and then stops working, with no change in taste, flow or appearance to warn you. Replace on the rated gallons rather than on symptoms, and size the unit for the flow it will actually see.
Off-gassing, boiling and ascorbic acid
Free chlorine is volatile, so water left standing uncovered loses much of it over hours, and boiling accelerates that considerably. Both are practical for a jug of water for cooking, aquarium top-up or a pot of coffee, and impractical for anything at household scale. Ascorbic acid, ordinary vitamin C, neutralizes chlorine chemically and almost instantly, which is why it is the medium in most dechlorinating shower filters and bath balls and a standard trick for filling a pond or a fish tank. It leaves a small amount of harmless residue and it does not filter anything else out. None of these methods touch metals, hardness, nitrate or bacteria.
Chloramine changes the answer
Many utilities use chloramine, a combination of chlorine and ammonia, because it is more stable in the distribution system. It is also considerably harder to remove. It does not off-gas meaningfully, boiling is ineffective, and ordinary activated carbon removes it slowly and incompletely. What works is catalytic carbon, a carbon treated to accelerate the reaction, in a bed large enough to give real contact time. Ascorbic acid neutralizes it as well, which is why vitamin C shower filters work on both. Find out which your utility uses before buying: every community water system publishes an annual Consumer Confidence Report and the EPA maintains a finder for them.
Whole house or point of use
Decide by where the chlorine bothers you. If it is taste in drinking water and coffee, a point-of-use carbon filter at the kitchen tap is the efficient answer. If it is dry skin and hair, or the smell filling the bathroom during a shower, the exposure is in the bathroom and a shower filter or a whole-house carbon system is the fix, since a kitchen filter does nothing for a shower. A whole-house unit also protects downstream equipment: chlorine damages reverse osmosis membranes and shortens the life of softener resin, so a carbon stage ahead of them is common practice. Our chlorine treatment guides cover sizing for a household's peak flow.
Questions people ask about how to remove chlorine from water
Does boiling remove chlorine from water?
It removes much of the free chlorine, since chlorine is volatile and leaves with the steam. It does not work on chloramine.
How long does chlorine take to evaporate from standing water?
Free chlorine largely dissipates over several hours in an open container, faster in a wide shallow one, and faster still if the water is warm.
Does vitamin C really neutralize chlorine?
Yes. Ascorbic acid reacts with both chlorine and chloramine almost immediately, which is why it is used in shower filters and for filling ponds.
Will a fridge filter remove chlorine?
Yes, it is a carbon cartridge, so it handles chlorine taste well. It works only on the water and ice it feeds, and it exhausts on a schedule.