Best Water Softeners: Only Models Certified to NSF/ANSI 44
Buy a softener certified to NSF/ANSI 44, the softener standard. We found 7 certified models sold on Amazon as the exact model. The Kenmore 350 costs the least per grain of capacity today, at about $19.73 per 1,000 grains. Use the calculator below to check the size.
NSF lists this exact model (625.383500) under NSF/ANSI 44, the softener standard, and notes it meets the efficiency rating for salt and water use.
Check price on AmazonBigger home? Kenmore 420 (40,000 grains) ($825.41) →Amazon prices as of October 20, 2026 at 2:01 PM ET. Prices can change; the price on Amazon is the one that counts. As an Amazon Associate we earn from qualifying purchases; some links are affiliate links and we may earn a commission at no extra cost to you. Disclosure.
What size do you need?
Uses 50 gallons per person a day (Water Quality Association: a home of four uses about 200 gallons a day) and one week between regenerations, plus about 25% spare. 1 grain per gallon = 17.1 mg/L. Don't know your hardness? Test it first.
Every certified softener we found on Amazon
Each one is listed for NSF/ANSI 44 by its exact model number. Rows are ordered by price per 1,000 grains of capacity. Prices as of October 20, 2026 at 2:01 PM ET. Certification listings checked October 14, 2026. Rows the calculator says are big enough are marked.
| Softener | Capacity | Certified by | Price | Per 1,000 grains | |
|---|---|---|---|---|---|
| Kenmore 350 Model 625.383500 | 32,000 grains | NSF NSF/ANSI 44 | $631.46 | $19.73 | Amazon → |
| GE GXSH35W Model GXSH35W | 35,000 grains | IAPMO R&T NSF/ANSI 44 | $699.00 | $19.97 | Amazon → |
| Kenmore 420 Model 625.384200 | 40,000 grains | NSF NSF/ANSI 44 | $825.41 | $20.64 | Amazon → |
| Aquasana SimplySoft WH-SF40 Model WH-SF40 | 40,000 grains | IAPMO R&T NSF/ANSI 44 | $848.00 | $21.20 | Amazon → |
| North Star NSC42 Model NSC42 · sold by Voomi Supply | 42,055 grains | NSF NSF/ANSI 44 | $1297.16 | $30.84 | Amazon → |
| GE GXMD30W (softener + filter) Model GXMD30W | 30,000 grains | IAPMO R&T NSF/ANSI 44 | $999.00 | $33.30 | Amazon → |
| North Star NSC31 Model NSC31 · sold by TERRATREE INC | 31,300 grains | NSF NSF/ANSI 44 | $1374.87 | $43.93 | Amazon → |
North Star softeners are sold on Amazon by plumbing supply stores, not by Amazon, so their prices run higher. The GE GXMD30W adds a carbon filter for chlorine taste. Whirlpool, Morton and Rheem softeners are certified too, but we did not find the exact models on Amazon, only parts.
Test your water first
A softener only makes sense if your water is hard. Hard water leaves white crust on faucets, spots on glasses and soap that won't lather. To get a number:
- City water: look for "hardness" in your water utility's yearly water quality report (often called a Consumer Confidence Report).
- Test strips: dip one in cold tap water and match the color. It gives a rough range, which is enough to size a softener. Varify water hardness test strips ($9.99) → We found no certification for hardness test strips.
- Well water: a lab test is best, and it will also show iron, which affects which softener you need.
Under 3.5 grains per gallon is soft, 3.5 to 7 is moderately hard, 7 to 10.5 is hard and above 10.5 is very hard. That is the US Geological Survey scale (60, 120 and 180 mg/L), converted to grains per gallon.
Popular softeners with no certifier listing
We searched the NSF, IAPMO and WQA listings on October 14, 2026 and found no NSF/ANSI 44 listing for these brands sold on Amazon: Aquasure, iSpring, SpringWell, Fleck-based kits (for example DuraWater and AFWFilters). They may work. But no certifier has tested and listed them, so we don't recommend them over a certified model at a similar price.
Salt-free "softeners" don't soften water
Salt-free units (also called conditioners or descalers) do not remove hardness. The Water Quality Association says they "do not provide a reduction of total calcium or magnesium" and are not "proven to achieve soft water." Some may reduce scale buildup in pipes. No US certifier lists any of them as a softener. If you want soft water, you need a salt-based softener.
Shower filters, magnets and drinking water filters don't soften water either.
Which salt to buy
Softener salt is certified to NSF/ANSI 60 (chemicals used in drinking water). NSF lists Diamond Crystal and Morton softener salts for regenerating softener resin. Pellets work in almost every softener and leave less mush in the tank than rock salt.
Diamond Crystal Bright & Soft salt pellets, 50 lb ($34.99) → NSF/ANSI 60 listing, Cargill: Diamond Crystal Bright & Soft (certified for water softener resin regeneration). Heavy bags often cost less at a hardware store; compare before you buy.
Potassium chloride works instead of salt and avoids adding sodium to your water. It costs more. Check your softener's manual before you switch.
Questions people ask
What certification should a water softener have?
NSF/ANSI 44. It is the standard for home water softeners. A certified softener was tested to remove hardness to its rated capacity and is listed by a certifier such as NSF, IAPMO or WQA by its exact model number.
What size water softener do I need?
Multiply the people in your home by 50 gallons a day (the Water Quality Association's figure for a typical home), then by your water's hardness in grains per gallon, then by 7. That is the grains your softener removes in a week. Pick a softener with at least that much capacity plus about 25% spare.
Do salt-free water softeners work?
They do not soften water. The Water Quality Association says these devices do not reduce calcium or magnesium and are not proven to make soft water. Some may reduce scale buildup. No US certifier lists them as softeners.
How do I find out how hard my water is?
Use a hardness test strip in a glass of cold tap water, or look for hardness in your water utility's yearly water quality report. For a well, a lab test is the most accurate. Divide milligrams per liter (mg/L or ppm) by 17.1 to get grains per gallon.
Is Aquasure or iSpring certified?
We searched the NSF, IAPMO and WQA listings on October 14, 2026 and found no listing for Aquasure, iSpring or SpringWell softeners. They may work, but no certifier has listed them.
Salt or potassium for a water softener?
Both work. Salt (sodium chloride) is cheaper. Potassium chloride avoids adding sodium to your water, which the Water Quality Association notes for people limiting sodium. Check your softener's manual before you switch.
Sources, and what we did and did not check
- NSF/ANSI 44 listings: info.nsf.org, read October 14, 2026. North Star and Kenmore models carry NSF's efficiency-rated note.
- IAPMO R&T certificates W-29819 (GE) and WP-16886 (Aquasana): pld.iapmo.org, read October 14, 2026.
- WQA Gold Seal listings: find.wqa.org, searched October 14, 2026.
- Water Quality Association, Getting Smart with Softeners (household water use, potassium chloride) and scale deposits (salt-free devices).
- NSF/ANSI 60 listings for Morton Salt and Cargill (Diamond Crystal): info.nsf.org, read October 14, 2026.
- Amazon listings and prices: Amazon's product API. We matched each listing's brand and model to the certified model. A price shows only if we read it in the last 24 hours.
- We did not: test any softener, check install needs (most need a plumber and a drain), or check every softener sold. The 25% spare and one-week cycle are common sizing rules, not a standard.
Related: white scale and spots · whole-house filters · filter and softener types · our method