Best water softener: the specs compared
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If you want a softener with independently checked numbers, the Whirlpool, Rheem and Morton cabinet softeners all appear on NSF's live NSF/ANSI 44 listings for hardness reduction and salt efficiency. Whirlpool's WHES48 has the highest flow and hardness limit of that group. Aquasana's SimplySoft is a two-tank design that Aquasana says is certified through IAPMO. SpringWell's SS series goes up to 80,000 grains but publishes far fewer specs and no certification.
We haven't tested these softeners. Every figure comes from the manufacturer's own manual or product page, and we checked certifications against NSF's online listings on November 10, 2026. No ratings, no scores. The best one for you is the one sized to your water: try the size calculator first.
The comparison table
| Model | Capacity at max salt (grains) | Capacity at a mid setting | Resin | Service flow | Max hardness | Max clear-water iron | Certification |
|---|---|---|---|---|---|---|---|
| Whirlpool WHES30 | 31,700 (13.1 lb) | 26,600 (7.8 lb) | 0.82 cu ft | 7.3 gpm | 95 gpg | 8 ppm | NSF/ANSI 44 (NSF listed) |
| Whirlpool WHES40 | 40,000 (15.5 lb) | 31,600 (9.0 lb) | 1.14 cu ft | 7.6 gpm | 125 gpg | 10 ppm | NSF/ANSI 44 (NSF listed) |
| Rheem RHS42 | 42,400 (16.3 lb) | 29,900 (8.0 lb) | 1.20 cu ft | 9.9 gpm | 140 gpg | 11 ppm | NSF/ANSI 44, plus barium and radium (NSF listed) |
| Morton M45C | 45,400 (17.2 lb) | 35,700 (9.9 lb) | 1.26 cu ft | 10.0 gpm | 120 gpg | 12 ppm | NSF/ANSI 44 (NSF listed) |
| Whirlpool WHES48 | 48,000 (18.1 lb) | 37,900 (10.5 lb) | 1.33 cu ft | 11.9 gpm | 160 gpg | 12 ppm | NSF/ANSI 44 (NSF listed) |
| Aquasana SimplySoft WH-SF40 | 40,000 (headline) | 13,269 at 3 lb | 1 cu ft | 11.02 gpm | 200 gpg | 1 ppm | NSF/ANSI 44 via IAPMO (maker's claim) |
| SpringWell SS1 / SS4 / SS+ | 32,000 / 48,000 / 80,000 | Not published | Not published | 11 / 13 / 20 gpm | Not published | Not published | None stated |
On a phone, swipe the table sideways to see every column. "Capacity at a mid setting" is the middle salt dose each manual lists. It's a fairer comparison of everyday capacity than the headline number, which needs the most salt.
Who makes what
The Whirlpool, Rheem and Morton manuals all say the softeners are manufactured and warranted by Water Channel Partners of Eagan, Minnesota, and NSF lists them under that company. They share a design: an all-in-one cabinet with the resin tank inside the salt tank, demand-initiated regeneration that varies the salt dose, a 20 to 125 psi operating range, and a 24-volt plug-in power supply. The differences are capacity, flow, iron limit and warranty.
The models
Whirlpool WHES30
The smallest here, for one or two people or softer water. Amazon lists it as the WHES30E; Whirlpool's own documents call it the WHES30.
- Capacity
- 12,500 grains at 2.4 lb of salt; 26,600 at 7.8 lb; 31,700 at 13.1 lb
- Salt efficiency
- 5,094 grains per pound at its lowest setting
- Water per regeneration
- 35.2 gallons at the maximum salt setting
- Flow
- 7.3 gpm rated (NSF's listing shows 7.6)
- Limits
- 95 gpg hardness, 8 ppm clear-water iron; salt tank holds 175 lb
- Warranty
- 1 year full parts and labor (5 years if you use Whirlpool's cleaner every four months and keep proof); 10 years on the tanks; 3 years on the control board
Check current price (link coming soon)
Whirlpool WHES40
A middle size that suits many families on moderately hard water. Sold on Amazon as the WHES40E.
- Capacity
- 17,300 grains at 3.4 lb; 31,600 at 9.0 lb; 40,000 at 15.5 lb
- Salt efficiency
- 5,090 grains per pound at its lowest setting
- Water per regeneration
- 37.1 gallons at the maximum salt setting
- Flow
- 7.6 gpm (matches NSF's listing). Connects to plumbing up to 1ΒΌ inches.
- Limits
- 125 gpg hardness, 10 ppm clear-water iron; 200 lb salt
- Warranty
- Same as the WHES30
Its 7.6 gpm flow is on the low side for a big house with several showers running at once. If that's you, look at the Rheem, Morton or WHES48.
Check current price (link coming soon)
Rheem RHS42 (Preferred Plus)
Close to the WHES40 in capacity but with a noticeably higher flow rate, and the only model here whose NSF listing also covers barium and radium reduction.
- Capacity
- 12,400 grains at 2.5 lb; 29,900 at 8.0 lb; 42,400 at 16.3 lb
- Salt efficiency
- 5,010 grains per pound at its lowest setting
- Water per regeneration
- 45.9 gallons at the maximum salt setting
- Flow
- 9.9 gpm
- Limits
- 140 gpg hardness, 11 ppm clear-water iron
- Extra claims
- Barium (10 mg/L reduced to 2.0) and radium 226/228 (25 pCi/L reduced to 5), NSF listed
- Warranty
- 1 year full (5 years with Rheem's cleaner every four months); 10 years on the tanks; 3 years on the control board. Warranted by Water Channel Partners.
Check current price (link coming soon)
Morton M45C
Wi-Fi connected, with a 10 gpm flow and a high iron limit for its size.
- Capacity
- 13,233 grains at 2.6 lb; 35,700 at 9.9 lb; 45,400 at 17.2 lb
- Salt efficiency
- 5,070 grains per pound at its lowest setting
- Water per regeneration
- 43.7 gallons at the maximum salt setting
- Flow
- 10.0 gpm
- Limits
- 120 gpg hardness, 12 ppm clear-water iron
- Warranty
- 1 year full (5 years with Morton's cleanser every four months); 10 years on the tanks; 3 years on the control board
Check current price (link coming soon)
Whirlpool WHES48
The largest of the cabinet models, with the highest flow (11.9 gpm) and hardness limit in the group, and a longer base warranty than the smaller Whirlpools.
- Capacity
- 14,200 grains at 2.8 lb; 37,900 at 10.5 lb; 48,000 at 18.1 lb
- Salt efficiency
- 5,090 grains per pound at its lowest setting
- Water per regeneration
- 44.2 gallons at the maximum salt setting
- Flow
- 11.9 gpm
- Limits
- 160 gpg hardness, 12 ppm clear-water iron; 200 lb salt
- Warranty
- 2 years full parts and labor (10 years with Whirlpool's cleaner every four months); 10 years on the tanks; 3 years on the control board
Check current price (link coming soon)
Aquasana SimplySoft WH-SF40 and WH-SF60
A two-tank softener: a separate resin tank and brine tank, which gives a bigger salt store (230 lb) and a high hardness limit of 200 gpg. The catch for well owners is its iron limit of just 1 ppm. Aquasana says it's certified by IAPMO to NSF/ANSI 44; IAPMO's directory didn't load for us, so we couldn't confirm the listing ourselves.
- Capacity
- 40,000 or 60,000 grains (headline). The data sheet gives 13,269 grains at 3 lb of salt for the 40,000 model, 4,423 grains per pound.
- Resin
- 1 cubic foot (WH-SF40), 1.5 cubic feet (WH-SF60)
- Flow
- 11.02 gpm rated, 15.5 gpm peak (WH-SF40)
- Limits
- 200 gpg hardness, 1 ppm ferrous iron, pH 6.5 minimum
- Warranty
- Control valve 5 years; pressure vessel and brine tank 10 years; install kit 12 months. 90-day satisfaction guarantee.
Check current price (link coming soon)
SpringWell SS1, SS4 and SS+
Also two-tank, and the only range here that goes up to 80,000 grains, for large homes or very hard water. SpringWell publishes much less detail than the others: no resin volume, no maximum hardness or iron, no salt or water per regeneration, and no certification. An NSF/ANSI 44 search for SpringWell returned no products. Its warranty is lifetime on tanks, valves and fittings, with 5 years on the electronic head.
- Capacity
- 32,000 (SS1), 48,000 (SS4), 80,000 (SS+)
- Flow
- 11, 13 and 20 gpm in the spec table; 9, 12 and 20 in the size guide on the same page
- Limits
- 25 to 80 psi, pH 6.5 to 10
Check current price (link coming soon)
More on SpringWell and Aquasana side by side: SpringWell vs Aquasana.
What about GE? GE's own product pages say its GXSH40V, GXSHC40N and GXSH45V softeners are no longer manufactured, so we've left them out even though some stores still list them.
How to choose between them
- Size first. Use the calculator, then look at each model's capacity at a mid salt setting, not just the headline.
- Check the flow rate against your house. The cabinet models run from 7.3 to 11.9 gpm. A softener that can't keep up lets the pressure drop when several taps run at once.
- On a well, check the iron limit and compare it with your lab result. If you're near the limit, an iron filter ahead of the softener is the safer plan.
- Prefer a certification you can look up. NSF's listings are public; search for the model.
- Read the warranty conditions. Several "5-year" and "10-year" full warranties depend on buying the maker's cleaner and using it every four months, and keeping proof.
- Think about salt and water. The running cost calculator turns these specs into dollars.
Common questions
What's the best water softener for a family of four?
Size it first. On 10 gpg water, Penn State Extension's example family of four uses 3,000 grains a day, which points to a softener of around 32,000 to 40,000 grains. On harder water, or with iron, you'll need more. The size calculator works it out, then pick from the models in that range here.
Are Whirlpool, Rheem and Morton softeners the same?
They're closely related. All three manuals say the softeners are manufactured and warranted by Water Channel Partners, and their spec tables follow the same layout and the same demand-initiated design. The capacities, flow rates, iron limits and warranty extras differ by model, so compare the numbers rather than the badge.
What does NSF/ANSI 44 certification mean?
It's the American national standard for household softeners that work by ion exchange. A certified softener has been independently checked for hardness reduction, and if it's also listed as efficiency rated, it removes at least 3,350 grains of hardness per pound of salt and uses no more than 5 gallons of water per 1,000 grains at its rated setting. Look the model up on NSF's listings, or the certifier named in the manual, rather than relying on a logo.
Why don't you rate or score the softeners?
Because we haven't tested them. A score would suggest we know something about real-world reliability that we don't. What we can do honestly is put the manufacturers' published numbers side by side, flag where they contradict themselves, and check certifications against the certifier's own listings.
Can a water softener remove iron?
Small amounts of dissolved iron, yes. The manufacturer limits here run from 1 ppm (Aquasana SimplySoft) to 12 ppm (Whirlpool WHES48 and Morton M45C), but extension specialists put the practical limit lower, around 2 to 5 mg/L. Above that, put an iron filter first. See iron in well water.
Sources
All opened November 10, 2026.
- Whirlpool Water Solutions, WHES30 / WHES33 installation and operation manual, rev. H, January 30, 2025.
- Whirlpool Water Solutions, WHES40 / WHES44 installation and operation manual, rev. E, May 15, 2024, and the WHES40 product page, no date shown.
- Whirlpool Water Solutions, WHES48 installation and operation manual, rev. E, May 15, 2024.
- Rheem Water Treatment, RHS42 installation and operation manual, rev. F, January 10, 2022.
- Morton Water Softeners, M45C installation and operation manual, rev. F, January 31, 2025.
- Aquasana, SimplySoft 40,000 Grain product page, no date shown, and the WH-SF40 / WH-SF60 owner's manual (PDF), no date shown.
- SpringWell, Salt Based Water Softener System, no date shown, and the SS1 / SS4 installation instructions (PDF), no date shown.
- NSF, certified product listings under NSF/ANSI 44 for Water Channel Partners and SpringWell, current as of November 10, 2026; and a listing showing the efficiency rating criteria.
- GE Appliances, GXSHC40N and GXSH40V product pages, no date shown.
- Penn State Extension, Water Softening, updated September 8, 2025.
- Penn State Extension, Iron and Manganese in Private Water Systems, updated May 29, 2025.