Whole-house carbon filters: chlorine and chloramine out before the softener
A whole-house carbon tank takes out the chlorine or chloramine a utility adds, before the water reaches the fixtures or a softener. Chlorine wears out softener resin over the years, which is why Aquasure's manual caps it at 2 ppm and why the Fleck sellers push 10% resin for city water. The first question is which disinfectant your utility uses: standard carbon handles free chlorine, and chloramine calls for catalytic carbon.
Backwashing or upflow
Carbon beds pack down and trap sediment. The two tank designs deal with that differently.
Valve on top
Backwashing
A Fleck or similar valve reverses the flow every few days to lift and rinse the bed. It needs a drain and an outlet, and the supply has to deliver the backwash rate: 5.5 gpm for AFW's 1.5 cu ft tanks.
In/out head
Upflow
Water enters at the bottom and rises through the carbon, which keeps the bed from packing. No drain or power. AFW says its GreenFlo line is meant for water with little to no sediment, so a sediment filter goes in front on a well.
The media
Standard or catalytic carbon
Granular activated carbon removes free chlorine quickly. Catalytic carbon is treated to break down chloramine, which standard carbon handles slowly. AFW describes catalytic as "better suited for chloramine removal".
The order
Carbon first
Carbon goes ahead of the softener so the resin never sees chlorine. A salt-free conditioner on city water also needs carbon in front: Tier1 wants chlorine under 0.5 ppm.
Quick picks
The short answer for common situations. Each links to the full card below.
Both tanks, the flex line between them and a starter kit, in one order.
Compare the six
Flow is the continuous rating at full contact time where the seller gives one. Sellers rate similar carbon beds anywhere from 2.75 to 26 gpm, so the column says whose number it is.
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AFWFilters Digital Carbon backwashing filter, Fleck 5600SXT
Granular activated carbon in a 10 in tank under a Fleck 5600SXT filter valve, which backwashes the bed on a schedule to keep it from packing. It removes chlorine before the water reaches a softener or the fixtures.
Valve
Fleck 5600SXT digital filter valve, backwashing
Media
1.5 cu ft high-activity GAC
Flow
2.75 gpm service (AFW); backwash needs 5.5 gpm
Bypass
3/4 in (listing)
Suits: City water treated with free chlorine, as a pre-filter in front of a softener or on its own.
Weigh: AFW rates it at 2.75 gpm continuous for full contact time, far below what a house draws at peak, and backwashing needs 5.5 gpm from the supply plus a drain. Standard carbon is slow against chloramine; that is the catalytic model's job.
AFWFilters Digital Catalytic Carbon backwashing filter, Fleck 5600SXT
The same backwashing setup filled with catalytic carbon, which AFW describes as "better suited for chloramine removal than standard activated carbon". Chloramine is what many Florida utilities use as their residual disinfectant.
Valve
Fleck 5600SXT digital filter valve, backwashing
Media
Catalytic carbon, 1.5 cu ft (AFW)
Flow
3.0 gpm continuous; backwash needs 5.5 gpm
Suits: Utilities that disinfect with chloramine, which breaks down resin faster and passes through standard carbon.
Weigh: Same low continuous rating as the standard model (3.0 gpm) and the same 5.5 gpm backwash requirement. The listing gives 1.2 cu ft in one line and 1.5 in the title; AFW's page says 1.5.
Water enters at the bottom and rises through the carbon, which keeps the bed loose without backwashing. It runs with no drain or power, and the catalytic carbon handles chloramine.
Media
1.0 cu ft catalytic carbon
Flow
5 gpm; 1 bathroom, 1–2 people (listing)
Tank
10 in Vortech, 1 in connections, bypass (listing)
Head
Upflow in/out; no backwash, drain or power
Suits: A small household on chloraminated city water where no drain is near the main line.
Weigh: AFW rates the 1.0 cu ft size at 5 gpm for one bathroom and one or two people, and says GreenFlo is "intended for water supplies with little to no sediment". The 2.0 and 3.0 sizes were unavailable on Amazon when checked.
Two cubic feet of standard activated carbon in an upflow tank. No drain or power, and twice the carbon of the small catalytic unit for a whole house on free chlorine.
AFWFilters 48k softener, 10% resin, with 1.5 cu ft upflow carbon
The 48k Fleck softener and a 1.5 cu ft coconut-shell carbon upflow tank, sold together with the 24 in flex line that joins them and a starter kit with sanitizer, silicone lube and hardness strips. Carbon first, then the softener, in one order.
Softener
Fleck 5600SXT, 48,000 grain, 10% resin
Carbon
1.5 cu ft coconut-shell carbon, upflow, no backwash
Flow
Up to 12 gpm (AFW); the softener alone is rated 6–8 gpm
In the box
24 in flex line, sanitizer, silicone lube, hardness strips (listing)
Suits: City water with chlorine and hardness, where both tanks go in at once.
Weigh: AFW quotes this package at "up to 12 GPM" while rating the same 48k softener at 6–8 gpm service on its own listing. Use the lower figure when sizing for peak flow.
One cubic foot of coconut-shell carbon in a 9 x 48 in tank with an upflow head and bypass. A lower-cost way into a whole-house carbon tank.
Media
1 cu ft coconut-shell GAC (listing)
Tank
9 × 48 in, upflow head with bypass (listing)
Flow
"Up to 26 GPM" (listing)
Suits: Smaller houses on free-chlorine city water that want a tank instead of cartridges.
Weigh: The listing claims "up to 26 GPM". That is far above what other sellers rate a similar carbon bed for chlorine contact, so treat it as a pipe-flow figure and size from the bed volume.
Carbon removes chlorine in proportion to how long the water spends in the bed. AFW rates its 1.5 cu ft backwashing tank at 2.75 gpm continuous at full contact time, a figure meant for heavy chlorine loads, while upflow sellers quote 5 to 8 gpm for similar beds and one quotes 26. Two showers at the federal 2.5 gpm limit plus a washing machine come to roughly 6 to 8 gpm, and most of the day the draw is far lower, so a tank sized for the average still does most of the work. When chlorine taste comes through at peak, the next step is more carbon.
Sold off Amazon
Whole-house carbon sold elsewhere
Model
Media
Flow
Where sold
US Water Systems MatrixxBackwashing, Bluetooth valve
Catalytic coconut-shell carbon
5, 10, 15 and 20 gpm sizes
US Water Systems direct
SpringWell CF1, CF4, CF+Upflow with a 5-micron sediment filter
KDF and catalytic carbon
9, 12 and 20 gpm
SpringWell direct
SpringWell says its CF removes PFAS from city water. We found no NSF listing behind that claim, so it is reported here as the maker's statement.
