How to Remove Chlorine From Tap Water: 5 Methods Compared
UK water companies add chlorine to tap water as a disinfectant. It works extremely well, keeping our water safe through the distribution network. The downside is that residual chlorine reaching your tap creates a noticeable taste and smell that many people find unpleasant. Removing it is straightforward, with five effective methods ranging from completely free to specialised filter systems. Here's an honest comparison of all five, with effectiveness rates, time required, and which method is right for which situation.
The fastest, most effective way to remove chlorine from tap water is activated carbon filtration, which removes 95-98% of chlorine instantly as water passes through the filter. The cheapest method is leaving water in an open container for 24 hours so chlorine evaporates naturally (free, but slow). Boiling for 15-20 minutes works (effective but uses energy). Vitamin C (ascorbic acid) neutralises chlorine instantly with a small dose. Reverse osmosis systems are most thorough but expensive. For UK daily drinking, a carbon-based filter bottle is the most practical balance of speed, cost, and convenience.
Why Is There Chlorine in UK Tap Water?
UK water companies add chlorine as a disinfectant during the water treatment process. The Drinking Water Inspectorate requires water to be disinfected before it reaches consumers, and chlorine is the most cost-effective and reliable method. It kills harmful pathogens like E. coli, cryptosporidium, and other waterborne bacteria, then provides residual protection through the distribution network of pipes, reservoirs, and storage tanks.
The chlorine that reaches your tap is the residual amount left after treatment, typically 0.2-0.5 mg/l in UK water (well below the safety threshold). Heavily-treated regions like London and the South East tend to have stronger residual chlorine because the water travels longer distances through more complex distribution networks. Soft-water regions like Scotland and Wales generally have less noticeable chlorine taste because their source water needs less treatment.
Chlorine in tap water is safe to drink and meets the highest UK safety standards. The point of removing it is taste and odour, not safety.
Why Remove Chlorine From Tap Water?
UK tap water is safe to drink with chlorine in it. Removing chlorine isn't a safety upgrade, it's a quality upgrade. Here are the most common reasons UK households remove chlorine.
Better taste and smell
The most common reason. Strong chlorine taste makes tap water less pleasant, especially in heavily-treated regions like London and the South East.
Better tea and coffee
Chlorine affects the flavour profile of brewed drinks. Removing it reveals subtle flavours in tea and coffee.
Bread and fermentation
Chlorine inhibits yeast activity and can affect sourdough starters, kombucha, and home brewing.
Aquariums and ponds
Chlorine kills beneficial bacteria and is harmful to fish. Dechlorination is essential before adding tap water to aquariums.
Plants and gardens
Most plants tolerate chlorine, but sensitive species (orchids, carnivorous plants) benefit from dechlorinated water.
Pets
Some pets are sensitive to chlorine taste and drink less when water has noticeable chlorine. Filtering encourages better hydration.
5 Methods to Remove Chlorine: At a Glance
Side-by-side comparison of effectiveness, time required, cost, and best use case for each chlorine removal method. Ranked by everyday practicality for UK drinking water.
| Method | Effectiveness | Time | Cost | Best for |
|---|---|---|---|---|
| Activated carbon filter | 95-98% | Instant | £10-£50 + filters | Daily drinking |
| Letting water sit out | ~70-100% (slow) | 24 hours | Free | Pets, plants, aquariums |
| Boiling | ~30-50% (15 mins) | 15-20 min | Energy cost | Emergencies, cooking |
| Vitamin C | 99%+ (instant) | Instant | ~£5 per pack | Aquariums, baths, brewing |
| Reverse osmosis | 98-99%+ | Instant | £200-£600 | Whole-home, advanced needs |
Note on effectiveness: Percentages refer to typical chlorine reduction in standard UK tap water (0.2-0.5 mg/l residual chlorine). Results vary based on water conditions, equipment quality, and method execution.
Activated Carbon Filtration
Activated carbon (also called activated charcoal) is the most widely used dechlorination method globally and the most practical for UK daily drinking. The carbon's microscopic pore structure adsorbs chlorine molecules as water passes through, removing 95-98% of free chlorine instantly. The same filter typically removes microplastics, lead, heavy metals, and other contaminants in the same pass, which makes it a multi-purpose upgrade rather than a single-issue fix.
The Water Quality Association notes that a 10-inch granular activated carbon (GAC) cartridge with a flow of 0.5 gallons per minute can remove 95% of incoming chlorine for up to 2,500 gallons before needing replacement. NSF/ANSI Standard 42 specifically certifies filters for chlorine reduction.
How it works
Activated carbon has an enormous internal surface area (one gram has roughly 500-2,500 m² of surface area). When chlorinated water passes through, chlorine molecules bond chemically to the carbon surface and stay there, while the now-dechlorinated water passes through. The carbon eventually saturates and must be replaced, which is why filter bottles, jugs, and under-sink systems all have replacement filter schedules.
Available formats
Activated carbon filtration comes in several practical formats:
- Filter water bottles (Filtrate, BRITA Vital, LifeStraw): filter as you drink, portable, lowest entry cost
- Filter jugs (BRITA, ZeroWater, Aqua Optima): fill, pour, drink. Good for households
- Tap-mounted filters: attach to your kitchen tap, filter on demand
- Under-sink filters: plumbed-in systems, higher upfront cost but high capacity
- Whole-house filters: filter all incoming water, including showers and baths
- 95-98% chlorine removal, instant
- Removes microplastics, lead, heavy metals too
- No energy cost, no waiting
- Affordable entry (filter bottles from £15)
- Portable for travel and gym
- Improves taste and odour completely
- Filters need replacement every 2-3 months
- Standard carbon doesn't remove chloramine well (see below)
- Carbon filter quality varies significantly between brands
- Less effective on hot water
Activated carbon, in a bottle
Filtrate's alkaline filter system uses activated carbon plus mineral filtration to remove chlorine, microplastics, lead, fluoride, heavy metals, pesticides, and bacteria. TÜV SÜD safety inspected, replacement filters from £2.99. Free UK shipping over £50.
Shop Filtrate Filter Bottles →Letting Water Sit Out
Chlorine is volatile, meaning it naturally evaporates from water exposed to air. The simplest dechlorination method is to fill an open container with tap water and leave it sitting out for 24 hours. By the end of that period, most or all of the free chlorine will have evaporated. No equipment, no cost, no energy required, just patience.
This method is widely used by aquarium owners and gardeners. It's effective for free chlorine but has practical limitations: it doesn't work for chloramine (which doesn't evaporate easily), takes a full day, and requires open containers that can collect dust and contaminants. For drinking water, it's a slow option compared to instant filtration.
How to do it properly
- Fill an open container (jug, large glass, or bowl) with tap water
- Leave it uncovered at room temperature
- Stirring occasionally speeds the process
- Sunlight and warmth help (a sunny windowsill works)
- After 24 hours, most free chlorine has evaporated
- Cover and refrigerate for use within 2-3 days
- Completely free, no equipment needed
- No energy use, environmentally friendly
- Effective for free chlorine
- Used widely for aquariums and gardens
- Takes 24 hours, not practical for daily drinking
- Doesn't work on chloramine
- Open containers collect dust and contaminants
- Doesn't remove other contaminants (lead, microplastics)
- Risk of bacterial growth if left too long
Boiling Tap Water
Boiling accelerates chlorine evaporation. At 100°C, chlorine evaporates roughly 100x faster than at room temperature. Industry research suggests boiling tap water for 15-20 minutes removes most free chlorine, though peer-reviewed water research often cites 30-50% removal in standard 15-minute boils. The result depends heavily on initial chlorine concentration, pot shape, and how vigorous the boil is.
Boiling has practical drawbacks for routine dechlorination. It uses energy (a 15-minute boil costs roughly 8-12p in UK energy), takes time, and requires the water to cool before drinking. It's also useless against chloramine (chlorine bonded to ammonia), which is increasingly used by some UK water companies. For one-off cooking or emergency use, boiling works. For daily drinking, it's inefficient.
How to do it properly
- Fill an open pot with tap water
- Bring to a rolling boil on the hob
- Maintain rolling boil for 15-20 minutes (lid off)
- Allow to cool to room temperature before drinking
- Refrigerate any unused water within 2 hours
- Doesn't need special equipment
- Also kills any waterborne bacteria
- Useful for emergency use
- Good for cooking applications where water gets boiled anyway
- Lower removal rate than carbon or vitamin C methods
- Uses energy and costs money over time
- Doesn't work on chloramine
- Time-consuming for daily drinking
- Concentrates non-volatile contaminants (lead, fluoride) by reducing water volume
- Requires cooling time before drinking
Vitamin C (Ascorbic Acid)
Vitamin C, in either ascorbic acid or sodium ascorbate form, neutralises chlorine through a chemical reaction in seconds. The chlorine reacts with the vitamin C and converts to harmless chloride ions. The US Environmental Protection Agency has approved sodium ascorbate as a dechlorination agent for water discharge into sensitive ecosystems, and the same chemistry works in your kitchen. A small amount of vitamin C neutralises a large volume of chlorinated water almost instantly.
This method is popular among home brewers, aquarium owners, and people who want fast batch dechlorination without specialist equipment. It works on both chlorine and chloramine, which makes it more flexible than evaporation methods. The trade-off is taste: ascorbic acid is mildly sour. Most people don't notice it at the dosage required for chlorine neutralisation, but it's not entirely flavour-neutral.
How to do it properly
For typical UK chlorine concentrations (~0.5 mg/l):
- Add roughly 1mg of vitamin C per litre of water (a tiny pinch)
- Vitamin C tablets work, crushed and dissolved
- Powdered ascorbic acid (available cheaply online or at brewing suppliers) is more practical
- Stir briefly, the reaction is near-instant
- For larger volumes (bath, aquarium), 1g of vitamin C neutralises around 1000 litres at typical concentrations
- Instant, complete neutralisation
- Works on both chlorine and chloramine
- Cheap (one £5 pack lasts months)
- Natural and food-safe
- Used by professional aquarists and brewers
- Effective for any volume of water
- Adds a slight sour taste at higher doses
- Doesn't remove other contaminants (lead, microplastics)
- Requires accurate measurement for best results
- Less practical for individual glasses than batches
- Breaks down in storage if left in solution
Reverse Osmosis Systems
Reverse osmosis (RO) is the most thorough water filtration method available for home use. Water is forced through a semipermeable membrane under pressure, leaving behind dissolved chlorine, heavy metals, fluoride, microplastics, dissolved solids, and most other contaminants. RO systems typically include carbon pre-filters and post-filters, achieving 98-99%+ chlorine removal alongside almost everything else.
RO systems are typically installed under the kitchen sink with a dedicated tap for filtered water. They're the gold standard for households wanting hospital-level water purity. The trade-offs are significant cost (£200-£600 for the system, plus annual filter changes), water waste (most RO systems waste 2-4 litres of water for every 1 litre of pure water produced, though newer systems are more efficient), and they remove beneficial minerals along with contaminants, requiring some users to remineralise.
What's included in a typical RO system
- Sediment pre-filter (removes physical particles)
- Carbon pre-filter (removes chlorine before it damages the membrane)
- RO membrane (the main filtration step)
- Carbon post-filter (final polishing)
- Dedicated tap installed alongside main kitchen tap
- Storage tank under the sink
- Removes 98-99% of chlorine and almost everything else
- Permanent home installation
- Works on chloramine, fluoride, lead, heavy metals, microplastics
- Dedicated tap for filtered water on demand
- High capacity (no daily refilling)
- Significant upfront cost (£200-£600+)
- Wastes water (2-4L wastewater per 1L pure)
- Requires under-sink plumbing installation
- Removes beneficial minerals along with contaminants
- Annual filter replacement costs
- Not portable (whole-home solution only)
Which Method Should You Use?
The right method depends on what you're trying to do, how often, and how much you're willing to spend. Here's the practical decision tree.
For daily drinking water
Activated carbon filter (bottle, jug, or tap-mount). Best balance of speed, cost, and convenience for everyday use.
For aquariums & ponds
Vitamin C (instant) or sit-out method (24 hours). Both work; vitamin C is faster and works on chloramine.
For cooking applications
Either filter (instant) or boil (which often happens during cooking anyway). Carbon filters are easier for batch use.
For sourdough & brewing
Vitamin C for batch dechlorination. Sit-out method also works if you have 24 hours notice.
For sensitive plants
Sit-out method. Most plants tolerate chlorine; only sensitive species (orchids, carnivorous plants) need dechlorinated water.
For whole-home use
Reverse osmosis system or whole-house carbon filter. Premium investment for premium results.
For tightest budget
Sit-out method (free) or vitamin C (~£5 a year). Both work, just slower or with mild taste impact.
For travel & portability
Filter water bottle. Activated carbon in a portable format that works at home, gym, office, and travel.
For most UK buyers, the answer is the same
If you're trying to remove chlorine from tap water for daily drinking, an activated carbon filter bottle is almost always the right answer. It removes 95-98% of chlorine instantly, costs less upfront than reverse osmosis, doesn't require 24-hour planning like the sit-out method, doesn't need energy like boiling, and works on every glass of water you drink throughout the day. Filtrate's alkaline filter system goes further by removing microplastics, lead, fluoride, heavy metals, pesticides, and bacteria alongside chlorine.
- Filter bottles are the most practical pick for daily drinking, gym, office, and travel
- Filter jugs work for households who prefer batch filtering
- Sit-out method is the right answer for aquariums, plants, and one-off batches
- Vitamin C is the right answer for fast batch dechlorination and chloramine
- Reverse osmosis is the right answer for whole-home use with specific contaminant concerns
The simplest way to remove chlorine from tap water
Filtrate's Stainless Steel filter bottle removes chlorine, microplastics, lead, fluoride, heavy metals, pesticides, and bacteria from UK tap water as you drink. TÜV SÜD safety inspected, replacement filters from £2.99. Free UK shipping over £50.
Shop the Filtrate Stainless → Browse the rangeA Note on Chloramine (and Why It Matters)
Some UK water companies use chloramine instead of chlorine for residual disinfection. Chloramine is chlorine bonded with ammonia, and it lasts much longer in water than chlorine alone, which is why it's preferred for some long-distribution networks. The downside is that chloramine is significantly harder to remove than free chlorine.
The methods that work:
- Vitamin C: Works on both chlorine and chloramine equally well
- Catalytic carbon filters: Specially-treated carbon designed for chloramine removal (more expensive than standard activated carbon)
- Reverse osmosis: Removes both chlorine and chloramine via the membrane
The methods that don't work well:
- Sit-out method: Chloramine doesn't evaporate like chlorine; can take days or weeks
- Boiling: Chloramine takes much longer to break down via boiling than chlorine
- Standard activated carbon: Removes some chloramine but much less effectively than chlorine
If you live in an area with chloramine treatment, prioritise vitamin C, catalytic carbon filters, or reverse osmosis systems. Most UK water companies use free chlorine rather than chloramine, but check your specific provider if you're not sure which they use; this information is on the water company's website or annual quality report.
Frequently Asked Questions
Sources & references
- Drinking Water Inspectorate (DWI): UK water quality regulator
- DWI: Drinking Water 2024 annual report
- US Environmental Protection Agency: dechlorination methods and standards
- Water Quality & Health Council: drinking water disinfection research
- Culligan: chlorine removal industry research
- NSF/ANSI Standard 42 certification framework for chlorine reduction filters
- Pricing and product specs sourced from filtrate.uk, BRITA UK, LifeStraw Europe, and home reverse osmosis suppliers
This guide is updated periodically with refreshed research, UK water company practices, and updated guidance on dechlorination methods. All prices in GBP and accurate at time of writing.