Dechlorinating tap water is easy or awkward depending on two things: what the water is for, and whether your utility uses free chlorine or chloramine. The methods that work for a fish tank are overkill for a houseplant and inadequate for a household's drinking water, so the sensible approach is to start from the use rather than from the method.
Establish which disinfectant you have
This decides half the answer and costs nothing. The EPA notes that every community water system publishes an annual Consumer Confidence Report and maintains a finder for them, and the report names the disinfectant. Free chlorine will dissipate on its own given time, air and warmth. Chloramine is chlorine bound with ammonia, deliberately stable so it survives the distribution network, and it does not evaporate out of a bucket. Utilities also switch seasonally, which is why a method that worked last year may fail this spring.
Aquariums and ponds
This is the use with the least tolerance, because chlorine is directly toxic to fish and invertebrates and a water change is an immediate exposure. Use a dechlorinating product formulated for the purpose, dosed to the volume, which neutralises chlorine and, in the products that say so, chloramine and the ammonia it releases. Do not rely on standing water overnight, particularly on a chloraminated supply, and do not rely on a carbon cartridge whose remaining capacity you cannot see.
Brewing, plants and household cleaning
For brewing and fermentation, chlorine affects flavour and yeast, and the usual answers are a properly sized carbon filter or a measured dose of a campden style treatment, which handles chloramine as well. For seedlings and sensitive houseplants, standing water uncovered for a day works on free chlorine and a carbon filter is more reliable. Established garden plants and lawns tolerate normal municipal levels and need nothing at all, which is worth saying because a great deal of effort goes into this unnecessarily.
Drinking water for the household
Batch methods do not scale to daily use. An activated carbon filter removes chlorine at every draw with no planning, and on a chloraminated supply it must be catalytic carbon with adequate contact time, which usually means a larger cartridge or a slower flow. Boiling drives off free chlorine over several minutes but does little to chloramine and is impractical as a routine. Our tap water guide covers the supply differences that decide which equipment keeps up.
Questions people ask about how to dechlorinate tap water
Does leaving water to stand remove chlorine?
Free chlorine dissipates over hours in an open container. Chloramine does not, which is why the disinfectant type matters first.
What should I use for an aquarium?
A dechlorinating product dosed to the volume, choosing one that states it handles chloramine if your supply uses it.
Do garden plants need dechlorinated water?
Established plants and lawns tolerate normal municipal levels. Seedlings and some sensitive houseplants benefit; most watering does not.
What is best for daily drinking water?
An activated carbon filter, and catalytic carbon with longer contact time if the supply is chloraminated rather than chlorinated.