Water Softener Salt: Pellets vs Crystals vs Potassium

Side-by-side

Evaporated pellets

Pellets start as high-purity salt and get compressed into chunks. Diamond Crystal says the larger size of pellets and cubes may make them less likely to bridge than smaller crystals. That's the main reason we'd pick them for a typical basement softener. Some pellets include a small amount of additives meant to limit caking and mushing.

Iron-fighting pellets are a variant for well water with some iron. Morton says its Rust Defense pellets remove about 10 times more iron than plain salt per regeneration, based on its own lab testing. They help with clear-water iron but don't replace an iron filter on a badly iron-laden well.

Solar crystals

Solar salt comes from salt water evaporated in shallow outdoor ponds. It's high purity and usually cheaper than pellets. The catch is size: smaller pieces pack tighter and bridge more easily, especially in humid spaces. A few softener makers prefer one type over the other, so check the manual. Diamond Crystal recommends following the softener manufacturer's directions on salt type.

Water softener rock salt

Rock salt is mined and sold with the least processing. It's cheap, and it does soften water, but the dirt and insoluble minerals that come with it settle in the brine tank as sludge. That sludge clogs the brine pickup and the injector. Hellenbrand's manual tells owners to inspect the salt tank at least once a year for insoluble buildup, and with rock salt you'll be cleaning it out far more often. Unless your softener's manual specifically allows it, buy pellets or crystals instead.

Potassium chloride

Potassium chloride works the same way as salt; the resin swaps hardness for potassium instead of sodium. Morton's version is labeled 99% sodium free. Minnesota's Department of Health suggests it for households that want less sodium in their drinking water from a softener.

It costs a good deal more per bag, and some softeners limit how much you load. The Whirlpool WHES48 manual says to keep no more than 60 pounds of potassium chloride in the tank at once. If you switch, read the manual for any setting change it calls for.

Can you mix them?

Diamond Crystal says different softener salt types can usually be mixed. There's no harm in finishing a bag of crystals on top of pellets. Mixing salt and potassium chloride just gives you a blend of the two.

What about "salt-free" crystals?

Template assisted crystallization (TAC) is a different technology, not a salt. It's the media used in salt-free conditioners, and it changes how hardness behaves rather than removing it. If that's what you're weighing, read salt-free vs traditional softeners.