For most water softeners, pellets are the safe default: they’re purer than other forms and, according to Culligan, may keep the brine tank cleaner, though they’re more prone to “mushing”. Crystals and solar salt cost less but solar salt is the type most prone to salt bridges, and block salt only suits softeners designed for it. Always check your manual first: Pentair’s, for example, recommends block salt or solar pellet salt for its models.
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Water softener salt types compared
| Type | What it is | Strengths | Watch out for |
|---|---|---|---|
| Pellets (evaporated or solar) | Salt pressed into pellets; Morton says no glue or binders are used | Purer, may keep the tank cleaner (Culligan) | More prone to mushing at the bottom of the tank |
| Solar salt / crystals | Salt from evaporated seawater or brine; Pentair describes solar salt as 98% pure | Reasonably priced, low in impurities | Culligan calls solar salt the type most prone to bridging |
| Block salt | Salt pressed into large blocks | Pentair: reasonably priced, low impurities, won’t cake | Only for softeners designed to take blocks |
| Rock salt | Mined salt in its natural form | Cheap | Culligan lists it among softener salts; check the insoluble content and your manual |
| Pellets with resin cleaner | Salt with an additive to fight iron | Morton suggests it for raw water over 2 ppm iron | Only needed if you have iron |
| Potassium chloride | Pellets of potassium chloride instead of sodium chloride | No sodium added to the water | More expensive and less efficient (Culligan); only sold as pellets (Morton) |
Pellets vs crystals: which should you buy?
The two problems that stop a softener working are both about how salt behaves in the brine tank:
- Bridging, a crust across the tank with a hollow underneath. Culligan says solar salt is most prone to it.
- Mushing, a sludge at the bottom that can block the brine intake. Culligan says pellets are more prone to it.
So neither form is perfect. In practice:
- Use what your manual lists. Pentair’s performance data sheet names sodium chloride pellets or solar salt; its manual describes block salt and solar pellet salt.
- If you’ve had a salt bridge, try pellets and keep the tank only about half full.
- If you’ve had mush, try crystals or solar salt and clean the tank out first.
- Don’t switch back and forth every bag; give one type a few months so you can see how it behaves.
When something goes wrong, our guide to a water softener not using salt shows how to find and fix a bridge or mush.
Does the salt type change how much you use?
For sodium chloride, not much: the salt per regeneration is set by the softener’s salt dose, not by the shape of the salt. What changes your salt use is the setting. Pentair’s smallest whole-house model removes 4,272 grains per pound on its low setting and 1,945 on high. At the NSF/ANSI 44 efficiency minimum of 3,350 grains per pound, a family of four on 10 gpg uses about 349 lb a year. Details in how much salt a water softener uses.
Potassium chloride is different: Culligan describes it as less efficient, so you’ll use more of it, and it costs more per bag.
Salt and sodium in your water
Softening with sodium chloride adds sodium to your water: Morton gives about 7.9 mg per litre for each grain per gallon of hardness removed, so 15 gpg water gains about 118 mg/L. A properly working softener shouldn’t make water taste salty, Morton adds, because the brine is rinsed out after regeneration. If you need to limit sodium, the options are potassium chloride, an unsoftened kitchen tap, or both; Morton says you can mix potassium chloride and salt in any ratio and switch without emptying the tank.
Can you use table salt or road salt?
Use salt sold for water softeners. Your softener’s manual lists the acceptable types, and products made for softeners are designed to dissolve cleanly in a brine tank. Morton notes its softener salt is not iodized. De-icing salt can contain additives and more insoluble material, which ends up as sludge in the tank.
Buying and storing salt
- Bag size: 40 lb is the common US size, 25 kg in the UK. For how long each lasts, see how long a bag of softener salt lasts.
- Price: a 40 lb bag of Morton crystals was $8.76 at Walmart when we checked on October 20, 2026, about 22 cents a pound. Prices vary by store and region.
- Storage: keep bags dry and off the floor so they don’t cake.
- Adding salt: Culligan suggests checking monthly and adding when the tank falls below about half full, without overfilling.
Frequently asked questions
Can I mix pellets and crystals?
Morton says its water softening products are compatible with each other. Mixing forms isn’t harmful, but if you’re fighting bridging or mush, stick to one type so you know which behaves better.
Which salt is best for well water with iron?
Morton suggests salt with a resin cleaner when raw water has more than 2 ppm of iron. Also add 5 to your hardness setting per ppm of iron, as Pentair’s manual advises.
Is solar salt bad for softeners?
No, Pentair recommends solar pellet salt and describes solar salt as 98% pure. It’s just more prone to bridging, so check the tank when you add salt.
Do I need to clean the tank when switching salt?
Not normally. Morton says you can pour potassium chloride on top of the remaining salt. If there’s mush at the bottom, clean it out before switching.
