Salt-based water softeners: Fleck systems by grain size, twin tanks and cabinets

A salt-based softener is the only kind that lowers the hardness reading. Hard water runs through a bed of resin beads that trade sodium for calcium and magnesium; when the beads are full, the valve rinses them with brine from the salt tank and sends the hardness down the drain. Size comes from your hardness and household, and the valve decides how it regenerates.

A twin-tank water softener beside its brine tank

Single tank, twin tank or cabinet

Every softener here uses the same ion exchange resin. What differs is the valve that runs it and how the tanks are packaged. How a water softener works walks through a regeneration cycle step by step.

Two tanks side by side

Single tank, metered

A resin tank with the valve on top and a separate brine tank. A metered valve counts gallons and regenerates once the resin is nearly spent, usually overnight. Fleck 5600SXT systems and the Aquasure Harmony are built this way.

Always one ready

Twin alternating

Two resin tanks under one valve, such as the Fleck 9100SXT. One softens while the other regenerates or waits, so there is never a stretch of hard water and the resin is used to the last grain.

All in one shell

Cabinet

The resin tank sits inside the salt bin. Store brands (GE, Whirlpool, Morton) use this layout. It fits tight spaces and holds less resin than a two-tank system at the same price.

Inside the tank

8% or 10% crosslink resin

Standard resin is 8% crosslink. Ten percent resin is tougher and stands up longer to chlorine and chloramine, which is why the Fleck sellers push it for city water.

Quick picks

The short answer for common situations. Each links to the full card below.

Two to five people, city water
Fleck 5600SXT 48,000 grain, 10% resin
The Fleck 5600SXT on 1.5 cu ft of 10% resin: the size most houses land on, with parts any Fleck dealer stocks.
Everything in one box
Aquasure Harmony Series 48,000 grain
Drain line, brine line, fittings and transformer included, and a manual that spells out pressure and chlorine limits.
Large household or 20+ gpg
Fleck 5600SXT 64,000 grain
Two cubic feet on the same valve, so it goes longer between regenerations.
Soft water at every hour
DuraWater Fleck 9100SXT twin tank, 48,000 grain
Two tanks under one valve: one is always ready while the other regenerates.
Small household, tight closet
DuraWater Fleck 5600SXT 32,000 grain
One cubic foot in a 48 in tank, for one to three people on moderately hard water.
One cabinet, an app
GE Smart Water Softener 35,000 grain
Salt bin and resin tank in one shell, WiFi reminders, and a capacity table at three salt settings.

Compare the six

Valve, resin and flow from each seller's or maker's page; figures that come only from the Amazon listing say so. Sellers rate the same 1.5 cu ft Fleck build anywhere from 6 to 12 gpm, so the flow column names whose number it is.

Product links on this page go to Amazon. If you buy through them, Which Water Softener earns a commission. How we pick and earn

Salt-based water softeners
Model	Valve	Resin	Service flow	Regeneration	Link
Fleck 5600SXT 48,000 grain, 10% resinSingle-tank softener, metered regeneration	Fleck 5600SXT	1.5 cu ft, 10%	6–8 gpm (AFW)	Metered	Amazon
Aquasure Harmony Series 48,000 grainSingle-tank softener, metered regeneration	Aquatrol (Aquasure)	48,000 grain	12 gpm max (listing)	Metered	Amazon
Fleck 5600SXT 64,000 grainSingle-tank softener, metered regeneration	Fleck 5600SXT	2 cu ft	10 gpm (AFW)	Metered	Amazon
DuraWater Fleck 5600SXT 32,000 grainSingle-tank softener, metered regeneration	Fleck 5600SXT	1.0 cu ft, 10%	Not published	Metered	Amazon
DuraWater Fleck 9100SXT twin tank, 48,000 grainTwin-tank softener, alternating	Fleck 9100SXT twin	2 × 1.5 cu ft	Not published	Twin alternating	Amazon
GE Smart Water Softener 35,000 grainCabinet softener with WiFi	GE smart valve	1 cu ft	8 gpm	Metered, WiFi	Amazon

Single-tank softener, metered regeneration

Fleck 5600SXT 48,000 grain, 10% resin

AFWFilters Fleck 5600SXT 48k with 10% crosslink resin

The common do-it-yourself build: Pentair's Fleck 5600SXT valve on a 10 x 54 in tank holding 1.5 cubic feet of 10% crosslink resin, which tolerates chlorinated city water longer than standard 8% resin. The valve counts gallons and regenerates only when the resin is close to used up.

Valve: Fleck 5600SXT, digital metered
Resin: 1.5 cu ft, 10% crosslink, preloaded
Tank: 10 × 54 in; brine tank holds 250 lb of salt (listing)
Flow: 6–8 gpm service, 9–10 gpm peak (AFW)
Ports: 1 in NPT with bypass (listing)
Warranty: 5 years valve, 10 years tank (AFW)

Suits: Two to five people on city or well water up to the high teens in grains per gallon, and an owner who will set the hardness and salt dose from the manual.

Weigh: You program it yourself, and the 3/4 in valve sets the flow ceiling for a large house with several showers running. The 48,000 figure is the capacity at the maximum salt dose; at a thriftier setting it delivers closer to two thirds of that.

View on Amazon

Single-tank softener, metered regeneration

Aquasure Harmony Series 48,000 grain

Aquasure Harmony Series AS-HS48D

A complete kit on Aquasure's own Aquatrol metered valve, with the drain line, brine line and transformer in the box. The owner's manual is unusually clear about limits: 25 to 125 psi, and chlorine or chloramine at 2 ppm at most before a carbon filter goes in front. A 64,000-grain version sits on the same listing.

Valve: Aquatrol digital metered, 3/4 in MNPT
Flow: 12 gpm maximum (listing)
Water: 25–125 psi; chlorine or chloramine 2 ppm maximum (manual)
In the box: Valve, resin tank and resin, brine tank, bypass, brine and drain lines, transformer
Warranty: 5 years valve, electronics and resin; 10 years tanks

Suits: A first softener install where everything should arrive in one box, on city water within the manual's chlorine limit.

Weigh: The valve is Aquasure's own, so parts and programming come from Aquasure and the wider Fleck parts trade does not apply. Aquasure rates the 48k for 4–5 bathrooms and 5–6 people; size it from your hardness instead.

View on Amazon

Single-tank softener, metered regeneration

Fleck 5600SXT 64,000 grain

AFWFilters Fleck 5600SXT 64k

Two cubic feet of resin on the same 5600SXT valve: more grains between regenerations for a large household or very hard water. AFW rates its 10% version of this build at 10 gpm service and 15 gpm peak.

Valve: Fleck 5600SXT, digital metered
Resin: 2 cu ft high-capacity resin (listing)
Flow: 10 gpm service, 15 gpm peak (AFW, 10% build)
In the box: Valve, resin tank, brine tank with safety float, bypass (listing)

Suits: Five or more people, or hardness in the 20s, where a 48k would regenerate every few days.

Weigh: Two cubic feet is near the top of what a 3/4 in 5600 valve is usually paired with, and the listing does not say 10% crosslink resin. For a big house with high peak flow, a 1 in valve or a twin tank is the step up.

View on Amazon

Single-tank softener, metered regeneration

DuraWater Fleck 5600SXT 32,000 grain

DuraWater Fleck 5600SXT 32k with 10% resin

One cubic foot of 10% crosslink resin in a 9 x 48 in tank under the 5600SXT valve, with a brine tank and bypass. The smallest standard Fleck size, and the one that fits a small household on moderately hard water.

Valve: Fleck 5600SXT, digital metered
Resin: 1.0 cu ft, 10% crosslink, preloaded (listing)
Tank: 9 × 48 in; brine tank 14 × 36 in with float (listing)
Flow: Not published; AFW's 1 cu ft build: 5 gpm service, 7.5 peak
Bypass: 1 in (listing)

Suits: One to three people with hardness under about 12 gpg, or a condo utility closet where a 54 in tank will not fit.

Weigh: DuraWater publishes no flow rating; AFW rates its own 1 cu ft 5600SXT at 5 gpm service and 7.5 gpm peak, which two showers and a washer can reach. Undersizing means regenerating every two or three days.

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Twin-tank softener, alternating

DuraWater Fleck 9100SXT twin tank, 48,000 grain

DuraWater Fleck 9100SXT twin alternating

Two resin tanks under one Fleck 9100SXT valve: one softens while the other regenerates or stands by, so the house has soft water around the clock and a spent tank regenerates right away, at any hour.

Valve: Fleck 9100SXT, metered twin alternating (listing)
Resin: 1.5 cu ft per tank, two 10 × 54 in tanks (listing)
Brine tank: 14 × 36 in with safety float (listing)
Bypass: 1 in plastic (listing)

Suits: Large households, very hard water, and houses where water runs at night (shift workers, irrigation off the softened line, a busy rental).

Weigh: Two tanks take more floor space and cost more than a single 64k. Each tank holds 1.5 cu ft, the 48,000-grain figure; the second tank adds standby, so a bigger tank is the answer for more grains between regenerations.

View on Amazon

Cabinet softener with WiFi

GE Smart Water Softener 35,000 grain

GE Appliances GXSH35W

A one-piece cabinet with the resin tank inside the salt bin, an app through SmartHQ, and a spec table more complete than most: 37,065 grains at 17.1 lb of salt, 32,636 at 9.8 lb, and 13,311 at 2.6 lb. NSF/ANSI 44 certified.

Capacity: 13,311 gr at 2.6 lb salt; 32,636 at 9.8 lb; 37,065 at 17.1 lb
Resin: 1 cu ft Indion 225 in a 10 × 35 in tank
Flow: 8 gpm, 9 psi drop
Water: Up to 165 gpg hardness, 5 ppm clear-water iron, 20–125 psi
Salt: 200 lb cabinet (listing)
Certification: NSF/ANSI 44

Suits: A laundry room or garage with no space for two tanks, and an owner who wants salt and usage reminders on a phone.

Weigh: Cabinet units hold less resin (1 cu ft here) than a Fleck build of the same price, and the valve is GE's own. Service flow is 8 gpm at a 9 psi drop.

View on Amazon

The grain rating depends on the salt

A softener's name gives its capacity at the maximum salt dose, roughly 15 lb of salt per cubic foot of resin. GE publishes the curve for its 35,000-grain unit: 37,065 grains at 17.1 lb of salt, 32,636 at 9.8 lb and 13,311 at 2.6 lb. Most installers set a Fleck valve between 6 and 10 lb per cubic foot, where each pound of salt removes more hardness, and accept about two thirds of the nameplate capacity. That is why the sizing calculator works from usable grains.

Sodium

Penn State Extension puts the added sodium at 7.5 mg per quart for each grain per gallon removed. At 12 gpg that is about 90 mg per quart. Potassium chloride works in the same softeners in place of sodium chloride; the salt guide covers the trade-offs.

Sold off Amazon

Store-brand cabinets and direct-sale Fleck builds publish specs worth comparing, though Amazon does not carry them. Morton's manual is unusually complete: the M34 uses 31.6 gallons of water per regeneration at its maximum salt dose.

Salt-based softeners sold elsewhere
Model	Capacity	Service flow	Where sold
Morton System Saver M34Cabinet, 0.91 cu ft resin	34,900 gr at 14.5 lb salt; 29,200 at 8.6 lb; 13,700 at 2.7 lb	7.8 gpm	Home centers
US Water Systems Fleck 5600SXTSingle tank, metered	26k to 70k, 0.75 to 2.0 cu ft	7 to 20 gpm peak by size	US Water Systems direct
AFW Fleck 2510AiQ 80kSingle tank, 1 in valve	80,000 gr, 2.5 cu ft 10% resin	20 gpm	AFWFilters store

An 80,000-grain Fleck build on Amazon runs the 3/4 in 5600SXT valve, which limits flow no matter how much resin is in the tank. A big house with high peak demand needs the 1 in 2510 valve or the 9100SXT twin.