Water filter type
Whole-house filtration
A filter plumbed into the main line where water enters the building, so every tap, shower, and appliance downstream is fed treated water.
What a whole-house filter actually changes
A whole-house filter sits on the main line, before the water splits off to the kitchen, the bathrooms, the laundry, and the water heater. Everything downstream is fed filtered water. That is the appeal, and it is also the limit worth understanding before you spend anything.
The media inside is almost always activated carbon, sometimes with a sediment stage ahead of it. Carbon is very good at the things that bother people about municipal water: the chlorine smell, the flat chemical taste, the faint swimming pool note in a hot shower. It is not a barrier against dissolved metals, salts, or microorganisms. Those need different physics.
The most common misunderstanding we correct on site is about lead. A carbon filter at the main line is upstream of nearly all the lead risk in an older building, because lead enters from the service line, from solder at joints, and from brass fittings closer to the tap. Filtering at the point of entry does nothing about metal picked up in the fifty feet of pipe after it.
Sizing, flow rate, and the mistake that causes low pressure
Filters are rated for a flow rate in gallons per minute. Fit one rated below the demand of the building and you get a pressure drop that shows up as a weak shower when the washing machine is running. The fix is not a bigger pump. It is a correctly sized housing in the first place.
We size on fixture count and on the incoming pressure measured at the hose bib, not on the square footage of the house. Two properties of the same size can have very different demand depending on how many bathrooms run at once.
Pressure drop also rises as the filter loads. A cartridge that gave good flow in month one and poor flow in month eight has not failed. It has done its job and reached the end of its life.
When we tell people not to buy one
If your water tastes fine and your only worry is a contaminant you read about, a whole-house carbon filter is unlikely to be the right purchase. It will not reduce nitrates, arsenic, fluoride, or hardness, and unless it carries a specific certification it will not reduce lead either.
If the concern is drinking water quality alone, treating one tap costs a fraction as much and covers more contaminants. A certified under-sink unit or a reverse osmosis system gives you broader coverage at the place you actually drink from.
If you rent, this is the wrong category entirely. The unit fixes to the building and stays there when you leave.
What it reduces, and under which standard
Each row names the NSF/ANSI standard the category is tested under. A standard describes what the test covers. It does not mean every unit on the market carries that certification, so check the specific model against its listing before you buy.
| Contaminant | Standard | Note |
|---|---|---|
| Chlorine taste and odour | NSF/ANSI 42 | |
| Sediment and particulates | NSF/ANSI 42 | |
| Lead | NSF/ANSI 53 | Only on models specifically certified for lead. Most whole-house carbon units are not. |
What it does not do
Every filter has a boundary. These are the things this one will not fix, listed so you can rule it out quickly if your problem is on the list.
- Hardness. A carbon filter does not soften water and will not stop scale.
- Dissolved solids, nitrates, and most salts. Those need reverse osmosis.
- Bacteria and viruses, unless a UV stage is added.
- Lead already picked up from pipes downstream of the filter, which is most of the lead risk in an older building.
When it fits
- You want chlorine taste and smell gone from every tap, not just the kitchen
- Visible sediment is fouling fixtures and appliances
- You are on city water and the complaint is aesthetic rather than a specific health contaminant
When it does not fit
- Your concern is lead from interior plumbing, which sits downstream of this filter
- You want to reduce dissolved solids or nitrates
- You rent, because the unit is fixed to the building
Space, services, and upkeep
Roughly 3 to 4 feet of clear space at the main line, with room to swing a housing wrench.
No drain connection is required. It needs no power. This is not a rental option, because it fixes to the building and stays there.
Replacement interval. Sediment pre-filter every 3 to 6 months. Carbon media every 3 to 5 years depending on volume and chlorine level.
Problems this is used for
We recommend this equipment against these confirmed problems. Each page explains how to confirm the problem before spending anything, and when treatment is not warranted.
- Chlorine and chloramine taste. Utilities add a disinfectant residual and are required to maintain it through the distribution network.
- Sediment and cloudy water. Sand, silt, rust flakes, or air.
Property types where this comes up
Common questions
Will a whole-house filter reduce lead?
Only if that specific model is certified under NSF/ANSI 53 for lead, and most whole-house carbon units are not. Even then it sits upstream of the pipework that contributes most of the lead in an older building, because lead dissolves out of the service line, the solder, and the brass fittings between the main and your tap. A filter certified for lead at the kitchen tap will usually reduce your actual exposure far more, for far less money.
Will it lower my water pressure?
Not if it is sized for the building's demand. Pressure loss happens when a filter rated for a lower flow than the property uses is fitted, which shows up as a weak shower whenever another fixture runs. We measure incoming pressure at an outside tap and size on fixture count rather than square footage. A gradual pressure drop over months is different: that is the cartridge loading up and telling you it is due for replacement.
How long does the carbon media last?
Three to five years for a tank-based media bed, and three to six months for a sediment pre-filter cartridge ahead of it. The real driver is volume and chlorine concentration rather than the calendar, so a large household on heavily chlorinated water reaches the end sooner. We set the interval at handover based on your usage and note it on the housing.
Other filter types to compare
If the notes above rule this out, these are the neighbouring options worth reading before you decide.
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