Best Water Softener Salt: Pellets vs Crystals, Iron Fighter or Potassium?
Quick answer: for most softeners, high-purity evaporated salt pellets are the safe choice. Diamond Crystal’s Bright & Soft pellets are typically 99.8% sodium chloride and made “for use in all water softeners.” Solar salt crystals are the economical option and work in most softeners too. If you get rust stains, use an iron-fighting salt. If you’d rather not add sodium, use potassium chloride. Avoid rock salt, which Whirlpool says is high in impurities, and check your softener’s manual for the salt it recommends.
How we chose: we haven’t tested these salts ourselves. Purity and additives come from Cargill’s product specs for Diamond Crystal and from Morton’s product pages. Advice on salt types comes from Diamond Crystal’s FAQ and Whirlpool’s softener manual, and health notes from NDSU Extension and Health Canada.
Which water softener salt should I buy?
Answer four questions to get the type of salt that fits your softener and your water.
Our pick: evaporated salt pellets
Choose your answers to see the salt that fits.
Types of water softener salt
| Type | What it is | Typical purity | Best for |
|---|---|---|---|
| Evaporated pellets | High-purity salt compressed into pellets; Bright & Soft has an additive to prevent mushing and bridging | 99.8% sodium chloride (Bright & Soft) | Any softener, including one-cabinet models |
| Solar crystals | Salt evaporated naturally by the sun and wind | 99.6% (Solar Naturals) | An economical choice for most softeners |
| Cubes | High-purity salt compacted for extra hardness | 99.8% (Hardi-Cube) | Any softener; less prone to mushing |
| Blocks | 50 lb compressed blocks | 99.8% (Bright & Soft block) | Only softeners whose manual allows blocks |
| Iron-fighting | Pellets or crystals with an FDA-approved rust-removing additive | 99.6% (Iron Fighter) | Water with iron and rust stains |
| Potassium chloride | A sodium-free salt alternative | 99.1% potassium chloride (Diamond Crystal) | Homes avoiding added sodium |
| Rock salt | Mined salt with more insoluble material | Lower; Whirlpool says it’s high in impurities | Avoid in home softeners |
Purity is Cargill’s “typical” value for each Diamond Crystal product. Cargill says its Diamond Crystal salts are NSF certified to NSF/ANSI/CAN 60, except its blocks, which are certified only as non-food compounds.
Pellets vs crystals: which is better?
Both work. Diamond Crystal says crystals, pellets and cubes “all soften water effectively.” The difference is shape and how they’re made: pellets and cubes are compressed, while crystals form naturally as the water evaporates. Most softeners can use any of them, but check your manual.
- Choose pellets for a one-cabinet softener, if you’ve had salt bridges or mush, or if you just want the safest default. Cargill sells its Bright & Soft pellets for all water softeners, says they’re virtually 100% water soluble, and adds an anti-bridging agent.
- Choose crystals if you have a two-tank softener and want to spend less. Cargill calls its Solar Naturals crystals a “clean, economical salt for all water softeners.”
Whirlpool recommends pellet, nugget or coarse solar salt with less than 1% impurities, and says to keep the salt level lower in humid areas to prevent salt bridges. If you keep getting bridges or mush, Diamond Crystal suggests trying a different form of salt. For fixing a bridge, see brine tank problems.
Sodium chloride vs potassium chloride
Diamond Crystal says both “can effectively regenerate many water softeners.” The difference is what ends up in your water: sodium chloride adds a little sodium, and potassium chloride adds a little potassium instead. NDSU Extension puts the sodium at about 8 mg/L for every grain per gallon of hardness removed, and the potassium works out to about 13.4 mg/L per gpg. See is softened water safe to drink? for what that means per glass.
- Health Canada advises people with kidney disease and some other conditions to avoid water softened with potassium chloride. Ask your doctor if you’re on a sodium- or potassium-restricted diet.
- If your softener has a salt setting, switch it to potassium chloride. Whirlpool, for example, lets you choose sodium chloride or potassium chloride.
- Morton’s usage advice is about the same for both: one 40 lb bag a month for its potassium chloride pellets, and two bags every two months for its Clean and Protect sodium pellets.
Do you need iron-fighting salt?
If you get orange rust stains, an iron-fighting salt helps. Cargill sells Iron Fighter for water with high iron: it has an FDA-approved rust-removing additive that Cargill says is considered non-toxic to septic tank bacteria. Morton’s version is Clean and Protect Plus Rust Defense. Diamond Crystal adds a limit, though: its Iron Fighter pellets handle moderate iron, and if the stains continue, it suggests a periodic iron-removal cleaner or a dedicated iron filter. Test your water, then see our guides to water softener cleaners and softeners and filters for iron.
How much salt to add, and how often
- Check monthly. Diamond Crystal says to check the salt level at least once a month and keep the tank at least half full, without overfilling it. Morton also says to keep it at least half full. The rest of the routine is in our maintenance checklist.
- Expect about one bag a month. Diamond Crystal says most households use about two 40 lb bags every 1–3 months, depending on hardness, water use and the softener.
- Using salt fast? Diamond Crystal’s first suspects are a hardness setting that’s too high and more water use. See hardness settings.
- Salt not going down? Look for a salt bridge, then see water softener not using salt.
- Mixing salts is fine in most cases, Diamond Crystal says, unless your softener’s manual asks for one type.
Salt is usually the biggest running cost. Our cost guide found 40 lb bags for about $5–$9 in store listings.
The salts we recommend
Salt is heavy, so compare the Amazon price with your local store before you buy; Amazon is handiest if you can’t lift 40–50 lb bags or have no store nearby.
Diamond Crystal Bright & Soft salt pellets (50 lb)
High-purity evaporated pellets for any softener, including one-cabinet models.
- Purity: typically 99.8% sodium chloride (Cargill)
- Solubility: virtually 100% water soluble, which Cargill says helps avoid brine tank clean-outs
- Additive: prevents mushing and bridging in the salt tank
- Certification: NSF/ANSI/CAN 60 (Cargill)
Morton Pure and Natural salt crystals (40 lb, 4-pack)
Morton describes these as high-purity, all-natural salt crystals for everyday soft water. Crystals are the economical choice for a two-tank softener.
Good to know: Morton doesn’t publish a purity figure for these. If you’d rather have a stated spec, Diamond Crystal’s Solar Naturals crystals are typically 99.6% pure.
Check price on AmazonDiamond Crystal Sun Gems Iron Fighter crystals (40 lb)
Large solar crystals with the Iron Fighter rust-removing additive, for softeners where the water has iron.
- Purity: typically 99.6% (Cargill)
- Additive: FDA-approved rust remover, considered non-toxic to septic bacteria
Good to know: Cargill says Sun Gems is available only in limited areas, and this listing has few ratings. Iron Fighter pellets and Morton’s Clean and Protect Plus Rust Defense are the store alternatives.
Check price on AmazonDiamond Crystal Potassium Chloride
A salt alternative that adds potassium instead of sodium. Cargill says it’s for all water softeners.
- Purity: typically 99.1% potassium chloride, with low insoluble content (Cargill)
- Bag: 40 lb
Good to know: switch your softener’s salt setting if it has one, and read the health notes first. Morton’s potassium chloride pellets are 99% sodium-free.
Check price on AmazonAt the store, Morton Clean and Protect pellets are the main alternative to Bright & Soft. Morton says they’re formulated to reduce bridging and mushing, and sells them in 25, 40 and 44 lb bags.
Frequently asked questions
Are pellets or crystals better for a water softener?
Both soften water effectively. Pellets are the safer default, especially for one-cabinet softeners and humid spots; crystals cost less and suit most two-tank softeners. Follow your softener’s manual if it names a type.
What salt should I use in a Whirlpool softener?
Whirlpool recommends pellet, nugget or coarse solar salt with less than 1% impurities, and not rock salt.
Can I use water softener salt to melt ice?
Diamond Crystal says its Solar Naturals crystals are suitable as an ice melter, following the directions on the bag, but it doesn’t recommend its pellets for that.
Can I mix different types of water softener salt?
In most cases, yes, says Diamond Crystal, unless your softener’s maker recommends a specific type.
How often should I add salt to my water softener?
Check it at least once a month and keep the tank at least half full. Most households use about two 40 lb bags every 1–3 months, per Diamond Crystal.
Is potassium chloride better than salt?
It works about the same for softening and avoids adding sodium, but it adds potassium instead, and Health Canada advises some people, such as those with kidney disease, to avoid it. See is softened water safe to drink?
Related guides
- Water softener maintenance: monthly to yearly checklist
- Water in the brine tank: how much is normal (and salt bridges)
- Water softener repair: common problems and DIY fixes
- Is softened water safe to drink?
- Salt-based vs salt-free water softeners
- How much does a water softener cost?
Sources
- Cargill, Diamond Crystal water softener salts: purity, additives, bag sizes and NSF/ANSI/CAN 60 certification, checked November 2026.
- Diamond Crystal, Water Softener Salt FAQs: salt types, sodium vs potassium, mixing, salt levels, bridges and mush, Iron Fighter limits and ice melt.
- Morton, water softener salt, and product pages for Clean and Protect, Pure and Natural and Potassium Chloride.
- Whirlpool, WHES48 installation and operation manual (7392327 rev. D, 2023): recommended salt, rock salt, humidity and the salt type setting.
- NDSU Extension, Water Softening (Ion Exchange), WQ1031 (revised May 2022): sodium and potassium added by softening.
- Health Canada, Guidance on Potassium from Water Softeners.
- Amazon listings for the four salts, checked November 2026.