Activated carbon filters: what they remove, and what they do not
Carbon is the cheapest way to make tap water taste better. It is not a cure-all, and an overdue cartridge can make things worse.
An activated carbon filter removes chlorine, bad tastes and odours from tap water. It does not remove dissolved salts, hardness or most microbes. If taste is your complaint, carbon is usually the right starting point. If it is anything else, look elsewhere.
The carbon is full of tiny pores, and the chemicals that cause taste and smell stick to the surface as the water passes through. That is why the filter works well for a while and then stops.
What does an activated carbon filter remove?
- Chlorine and chloramine taste. The most common reason people fit one.
- Odours. Earthy or musty smells in mains water often improve.
- Some organic chemicals. The range depends on the product, so check what it is certified for.
It is not designed to soften water, so a carbon cartridge will not stop scale. See hard water for that problem.
What does it leave behind?
| Concern | Carbon alone | What does the job |
|---|---|---|
| Chlorine taste | Reduces it well | Carbon is the right tool |
| Dissolved salts and minerals | Does not remove them | Reverse osmosis |
| Hardness and scale | Does not remove it | A water softener |
| Rust, silt and grit | Partly, and it clogs | A sediment pre-filter |
| Rainwater or bore water safety | Does not make it safe | Testing by an accredited laboratory |
Never treat a carbon filter as proof that tank, bore or dam water is safe to drink. Only an accredited (NATA) laboratory can tell you that.
Where do you fit one?
Carbon filters come as jugs, tap-mounted units, under-sink cartridges and whole-house housings. The under-sink filter page compares the kitchen options. A whole-house filter usually pairs carbon with a sediment stage.
Anything plumbed into the drinking water supply, under the sink or on the mains, counts as plumbing work. In most states and territories that means a licensed plumber.
Change the cartridge on schedule
Carbon cartridges do not fail loudly. They fill up and stop working, and a neglected one can hold bacteria. Change it on the maker's schedule, not when the water tastes off, and write the date on the housing. Skipping the change is the commonest way these filters go wrong.
Which type of carbon filter suits you?
Block carbon filters pack the carbon into a solid shape, so water has to pass through it. Granular carbon is looser and cheaper, but water can find channels around the grains. For most households the block type gives the more reliable result.
Look for a product certified to a recognised standard for the claim you care about, such as chlorine reduction. A box that only says it filters water tells you nothing. If a maker will not say what the filter removes, pick another maker.
When is carbon not worth buying?
If your water tastes fine, you do not need one. Australian mains water is treated and tested by the supplier, and a carbon filter adds nothing to its safety. It is a taste upgrade, not a safety device.
If your real problem is scale on taps and the hot water system, spend the money elsewhere. If the problem is a brown or cloudy supply, read our page on hard water and talk to your water supplier first, since the cause may be in the mains or the pipes inside your home.
What does a carbon filter cost to run?
The cost sits in the replacement cartridges, not the housing. Compare the cartridge life and the price of refills before you buy, because a cheap unit with an expensive cartridge costs more over a few years. Ask what a year of cartridges will run, and what the maker says about their life.
Frequently asked questions
What does an activated carbon filter remove from water?
It mainly reduces chlorine, bad tastes and odours, and some organic chemicals. It does not remove dissolved salts, hardness or reliably remove microbes.
How often should I change a carbon filter cartridge?
Follow the maker's schedule. Cartridges fill up without any warning, so changing by date is safer than changing when the taste turns.
Does a carbon filter make tank or bore water safe to drink?
No. Water from rain tanks, bores or dams should be tested by an accredited (NATA) laboratory before you drink it.
Does a carbon filter need a plumber to install?
A jug does not. A unit connected to the drinking water supply, such as under the sink or on the mains, generally needs a licensed plumber.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Sydney Water. Water supply, wastewater and stormwater services