Best water softener salt: pellets vs solar crystals vs potassium chloride, compared on published purity, insolubles and bridging risk

Do not buy a pallet of anything yet: a salt bridge, not the salt brand, is the usual reason a full brine tank still makes hard water, and it is diagnosed with a broom handle before a shopping cart.

How was this shortlist built?

Every figure on this page is the manufacturer’s published specification, read from the data sheet, SDS or product page named beside it on 2026-09-12, or the text of an NSF listing, an extension bulletin or an EPA advisory. Nothing was put in a brine tank and no salt carries a rating from this site.

The salts were compared on the lines a data sheet prints: minimum purity, maximum water insolubles, bag sizes, any built-in anti-bridging or anti-mushing measure, and an NSF/ANSI 60 entry in the NSF listing database. NSF/ANSI 60 is the standard for chemicals added to drinking water, and “listed” here means the database record, not the maker’s claim.

Bridging is a hard crust forming above the water line in the brine tank, leaving a hollow so no brine is drawn. Mushing is pellets breaking down into a sludge at the bottom that blocks the brine well. Both leave the softener regenerating with weak or no brine.

Three gaps are flagged rather than filled: no manufacturer data sheet for block salt was located, no purity figure for Diamond Crystal Potassium Chloride was read from a Cargill page, and Morton’s potassium chloride pellets were not found under Morton’s NSF/ANSI 60 listing.

How do the salts compare on paper?

Manufacturer figures. “Not published” means the cited document prints no value. Only listings confirmed as single bags this session are linked.

Diamond Crystal Bright & Soft pellets: buy it or skip it?

Buy it if the softener has an ordinary brine tank and you want the additive built into the bag. Cargill’s sell sheet rates the pellets up to 99.8% pure and formulated against mushing and bridging; the Cargill SDS puts the composition at 99.97% sodium chloride and 0.03% sodium hexametaphosphate.

Check price on Amazon

The sell sheet lists 25, 40 and 50 lb bags and a 20 kg bag; the linked listing is the 50 lb bag, Cargill item 100012423. Bright & Soft appears under Standard 60 in NSF’s listing for Cargill Salt.

The flaw to admit: the two Cargill documents give the same pellet different numbers, “up to 99.8%” on the sell sheet and 99.97% on the SDS, and neither prints a water insolubles line. Read the purity as approximate.

Skip it if the reason for buying is sodium: it is still sodium chloride. Alternative: Morton Clean and Protect pellets, the same class with a published insolubles maximum.

Morton Clean and Protect pellets: buy it or skip it?

Buy it if you want the pellet with the most complete data sheet. Morton’s product data sheet 3351 puts the minimum purity at 99.65% sodium chloride and water insolubles at 0.1% maximum; the NSF database lists the Clean and Protect series under Standard 60 for Morton Salt.

Morton’s product page says the pellets are formulated to reduce bridging and mushing and to keep the resin tank clean. Morton lists 25, 40 and 50 lb bags, the 40 lb bag as part F125000000.

No link: the only Amazon listings found this session were third-party 3-packs of 40 lb bags, 120 lb in total, under a generic brand, and this site does not link a pack it cannot confirm as the maker’s own. Buy it by the bag at a hardware store.

Skip it on a sodium-restricted diet, whatever the additive does for the resin. That decision sits with the reader’s physician, not with a bag of salt.

Morton Solar Salt crystals: buy it or skip it?

Buy it if the brine tank is a plain open tank and purity to two decimals is not the deciding line. Morton’s product data sheet 3370 rates the crystals at 99.5% minimum sodium chloride, 0.5% maximum other salts, 0.1% maximum water insolubles and 0.15% maximum surface moisture. Bags come in 40, 50 and 60 lb sizes, part F139830000 for the 40 lb bag.

The crystals carry no additive. Instead, Morton screens them to 5% maximum fines through a 12-mesh sieve, which the sheet says is to avoid a tendency to bridge in softener brine tanks. The sheet also states the product meets AWWA B200 and is certified to NSF/ANSI 60.

Skip it if the softener has a touch grid plate or a hydrosyphon system designed for pelletized vacuum salt: Morton’s own sheet says the crystals should not go in those tanks. Skip it if the tank has ever mushed, because a crystal carries no additive against it.

No link: the only Amazon listing found was a reseller 4-pack of 40 lb bags, 160 lb in total. Alternative: Bright & Soft pellets, which fit every tank type in the table.

Morton Potassium Chloride pellets: buy it or skip it?

Buy it if the water leaving the softener must carry as little added sodium as possible. Morton’s business page rates the pellets at a minimum of 98.1% potassium chloride, and the home page sells the 40 lb bag as “99% sodium free”; the linked listing is the single 40 lb bag from the Morton Store.

Check price on Amazon

The cost of the switch is product. NDSU Extension’s WQ1031 says about 10% more potassium chloride is used per backflush, and WQA’s Getting Smart with Softeners puts the required concentration 13 to 15% higher, noting that potassium chloride forms salt bridges more readily. Budget for the bigger number and check the tank monthly.

Skip it if cost per regeneration matters: the bag is 40 lb where the sodium pellets go to 50, and every regeneration draws more of it. Skip it if the softener manual gives a brine setting for sodium chloride only, since the manual decides the dose, not this page.

Two gaps stay open: Morton publishes no water insolubles figure for these pellets, and they were not found under Morton’s NSF/ANSI 60 listing. Diamond Crystal Potassium Chloride, the Cargill equivalent, does appear under Cargill’s Standard 60 listing, but its Amazon listing was unavailable with no restock date, so it is named and not linked.

Do you need a resin cleaner too?

Only if iron or sediment is reaching the resin, which is a well water problem more than a salt problem. EcoPure lists its EPCL cleaner as a 16 oz bottle used every 4 months for iron, rust and sediment.

Clack’s Res-Up is the other common name, and its SDS lists it as an acidic cleaner containing 10 to 30% phosphoric acid, dosed by the label, not tipped in.

A pellet that already carries an additive, Bright & Soft or Clean and Protect, covers routine use on city water. On a well with iron, the fix is an iron filter ahead of the softener, not a stronger cleaner behind it.

What goes wrong?

The tank bridges. A crust forms above the water line and the softener regenerates with plain water while the tank looks full. WQA names potassium chloride as the salt that does this most readily, and Morton’s 5% fines screen on solar crystals exists for the same reason.

Push a broom handle down the tank; if it breaks through a crust, that was the problem.

The tank mushes. Pellets dissolve into a sludge that blocks the brine well, which is what the sodium hexametaphosphate in Bright & Soft and the additive in Clean and Protect are formulated against. Crystals have no defence beyond their fines screen.

Insolubles build up. Morton’s 0.1% maximum on Clean and Protect and Solar Salt is 0.64 oz of grit per 40 lb bag, and it stays in the tank; rinsing the brine tank once a year is the remedy. A salt with no published insolubles figure gives no way to plan for it.

The salt runs out. WQA’s efficient target is 4,000 grains of hardness removed per pound of salt under the NSF/ANSI 44 capacity protocol, and one grain per gallon is 17.1 mg/L as calcium carbonate per WQA’s ion exchange fact sheet. The salt usage calculator turns those figures and a hardness reading into bags a year.

Frequently asked questions

Sources

1. Morton Salt, Clean and Protect pellets product data sheet 3351 (PDF) (manufacturer or vendor document)
2. Morton Salt, Clean and Protect pellets product page (manufacturer or vendor document)
3. Morton Salt, Solar Salt crystals product data sheet 3370 (PDF) (manufacturer or vendor document)
4. Morton Salt, Potassium Chloride pellets, business product page (manufacturer or vendor document)
5. Morton Salt, Potassium Chloride pellets, home product page (manufacturer or vendor document)
6. Cargill, Diamond Crystal Bright & Soft water softener salt pellets sell sheet (PDF) (manufacturer or vendor document)
7. Cargill, Diamond Crystal Bright & Soft safety data sheet (PDF) (manufacturer or vendor document)
8. NSF, Standard 60 listing for Morton Salt Inc. (standards or certification body)
9. NSF, Standard 60 listing for Cargill Salt (standards or certification body)
10. NDSU Extension, WQ1031 Water Softening (Ion Exchange), 2022 (PDF) (university or extension service)
11. WQA, Getting Smart with Softeners (PDF) (standards or certification body)
12. WQA, Ion Exchange fact sheet (PDF) (standards or certification body)
13. EPA 822-R-03-006, Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Sodium, 2003 (PDF) (government or regulatory source)
14. EcoPure, EPCL universal water softener cleaner product page (manufacturer or vendor document)
15. Clack Corporation, Res-Up water softener cleaner safety data sheet (PDF) (manufacturer or vendor document)