What does a whole house water filter remove?

1. Sediment + carbon covers particles, chlorine taste and smell at every tap and shower.
2. Hardness, fluoride and dissolved salts need different treatment.
3. UV is for tank and bore water. Reverse osmosis is for drinking water.
4. Only trust claims backed by an NSF/ANSI certificate that lists that contaminant.

The two core stages

Almost every whole house (point-of-entry) system in Australia starts with the same two stages, fitted where water enters your property, usually near the meter.

• Sediment. A pleated or spun cartridge that physically traps particles: silt, sand, rust flakes and pipe debris. This is the cartridge that turns brown. See why your filter goes brown.
• Carbon. A carbon block that reduces chlorine taste and odour by adsorption. Filters certified to NSF/ANSI 42 are, in NSF's words, certified to reduce aesthetic impurities such as chlorine and taste/odor. Where your supply uses chloramine, catalytic carbon with longer contact time is the better choice.

Because these stages sit at the point of entry, the shower, bath, washing machine and hot water system all get filtered water, not just the kitchen tap. That is the difference between whole house and under-sink.

Contaminant by contaminant

Here is what each stage does, and doesn't, do. "Certified" means only when the product's certificate lists that claim.

General capability by technology. A specific product may do more or less; its certificate is the only proof.

What a standard whole house filter doesn't remove

This is where a lot of marketing gets vague, so here it is plainly. Sediment and carbon do not remove:

• Hardness. Calcium and magnesium are dissolved minerals. The guidelines flag scale problems above 200 mg/L. That needs a scale conditioner or softener. See hard water and your hot water system.
• Fluoride and dissolved salts. These need reverse osmosis, which is why we put it at the drinking tap rather than on the whole house.
• Germs in tank or bore water. Carbon is not a disinfection stage. Tank and bore supplies need UV, and the UV needs clear water to work, which is why sediment goes first.
• Dissolved iron and manganese. A sediment filter catches them only once they've turned into particles.

Add-on stages, and when they make sense

We never add these by default. They're recommended only when your test results point to them. Browse the options on our add-ons page.

Where each stage belongs in the house

Not every stage should treat every litre. Putting the right stage in the right place keeps running costs sensible and flow strong.

• At the meter (whole house): sediment and carbon. These protect everything downstream: the hot water system from settling sediment, tap aerators and showerheads from grit, and every shower and bath from chlorine taste and smell.
• At the meter, if needed: a scale conditioner for hard water, or UV for a tank or bore. UV goes after sediment because particles can shade microbes from the light.
• At the kitchen (point of use): reverse osmosis. It's slower and produces some waste water, so it makes sense for the water you drink and cook with, not for flushing toilets or watering the garden.

This is why a sensible system is layered rather than one giant filter. Each layer does one job well, and you only pay for the layers your water needs.

Certification is the only proof

Anyone can print "removes 99%" on a box. In Australia, Standards Australia's AS 3497:2021 for drinking water treatment units now requires performance claims to be certified to NSF/ANSI standards, so there's a single method for checking them. NSF/ANSI 42 covers aesthetic claims like chlorine taste and odour. NSF/ANSI 53 covers health-related contaminants. NSF/ANSI 58 covers reverse osmosis, NSF/ANSI 55 covers UV, and NSF/ANSI 401 covers emerging contaminants.

Separately, any product connected to the water supply must carry WaterMark, the mandatory certification scheme overseen by the Australian Building Codes Board. When you compare quotes, ask for both: the WaterMark licence for the housings and the NSF/ANSI certificate for each claim.

How to tell it's working

You shouldn't have to take a filter on faith. Three simple checks:

• The sediment cartridge changes colour. On mains water it should look noticeably darker at each change. That's what it caught.
• Chlorine before and after. A free and total chlorine test at a tap before the filter and a tap after it shows the carbon stage working. When the after reading creeps up, the carbon is due.
• Flow stays steady. A correctly sized system shouldn't noticeably change your shower. A gradual drop means the sediment cartridge is loading up.

We do a before-and-after test at installation and give you the results, and if you're on the Care Plan we photograph every used cartridge.

How to know what your filter needs to remove

The table above is general. What matters is your tap. Hardness, chlorine or chloramine, iron and dissolved solids vary by suburb and supply, and even by the age of your pipes. A test tells you which rows apply to you, and that decides which stages are worth paying for. See what your filter catches for the stage-by-stage view, or look up your city's water.

Questions

Plumbing and installation details reviewed by a licensed plumber. See our editorial policy.