Potassium chloride and sodium chloride both regenerate a water softener; the difference is what ends up in your water and what it costs. Potassium chloride replaces the sodium that softening adds (Morton says by 99%), but it costs more and, according to Culligan and the Vermont Department of Health, softens less efficiently, so you use more of it. Sodium chloride is the cheaper, standard choice.
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Both are allowed under NSF/ANSI 44, the standard for residential softeners, which covers units regenerated with either sodium or potassium chloride. Here’s how they compare in practice, with the mineral figures for your hardness.
Potassium chloride vs salt at a glance
| Sodium chloride (salt) | Potassium chloride | |
|---|---|---|
| Adds to softened water | Sodium | Potassium |
| Softening efficiency | The baseline | Lower (Culligan, Vermont Dept. of Health) |
| Price | Lower | Higher (Culligan) |
| Forms | Pellets, crystals, solar salt, blocks | Pellets only (Morton) |
| Resin cleaner additives | Available in some products | Not in Morton’s potassium pellets |
| Chloride discharge | Baseline | Up to 20% less, Morton says |
| Covered by NSF/ANSI 44 | Yes | Yes |
What each adds to your water
A softener swaps calcium and magnesium for sodium or potassium, so the amount added depends on how hard your water is. Morton gives a rule for each: about 7.9 mg/L of sodium per grain per gallon removed, and about 32 mg of potassium per 8-ounce glass for every 10 grains removed. We’ve converted both to mg per litre:
| Hardness removed | Sodium added (salt) | Potassium added (KCl) |
|---|---|---|
| 5 gpg | 40 mg/L | 68 mg/L |
| 10 gpg | 79 mg/L | 135 mg/L |
| 15 gpg | 118 mg/L | 203 mg/L |
| 20 gpg | 158 mg/L | 271 mg/L |
| 25 gpg | 198 mg/L | 338 mg/L |
Potassium figures are higher by weight because a potassium ion is heavier than a sodium ion; each one replaces the same amount of hardness. The point for most households is simpler: with potassium chloride, softened water carries almost no added sodium.
Who should consider potassium chloride
- Anyone told to limit sodium. The Vermont Department of Health notes the EPA’s guidance level of 20 mg/L of sodium for people on a 500 mg/day sodium diet, and suggests checking with your health care provider. Morton, for its part, advises people with kidney disease, diabetes, heart disease or high blood pressure to ask a doctor before drinking potassium-softened water.
- Gardens watered from softened taps. Morton suggests potassium chloride where soil is already high in sodium, though most owners simply keep outdoor taps on hard water.
- Areas that limit salt discharge. Morton puts the cut in chloride discharge at up to 20%. It’s a reduction, not a fix: the MPCA’s advice for chloride-sensitive areas focuses on efficient, demand-initiated softeners and correct settings.
A cheaper alternative for the drinking-water concern is to leave the kitchen cold tap unsoftened, which Wessex Water and other UK water companies recommend for drinking and cooking.
Switching from salt to potassium chloride
- No need to empty the tank. Morton says you can pour potassium chloride on top of the salt that’s left, and mix the two in any ratio. It suggests 50/50 as a starting point.
- Check your manual. Your manual may give a separate setting or a higher dose for potassium chloride, because it regenerates less efficiently. If it says nothing, test whether the water stays soft between regenerations.
- Expect to buy more. Lower efficiency means more pounds per year than the figures in our softener salt tables, and each bag costs more.
- Mind the iron. Potassium chloride pellets have no resin cleaner. Morton suggests a product with a resin cleaner when raw water has more than 2 ppm of iron.
Taste
Morton notes that at 22 grains or more of hardness, potassium-softened water may taste metallic or bitter to some people. A properly working softener shouldn’t make water taste salty with either product, because the brine is rinsed out after regeneration.
Worked example
Family of four, 15 gpg. With sodium chloride, softened water gains about 118 mg/L of sodium, well above the 20 mg/L EPA guidance level Vermont cites for people on very low sodium diets. With potassium chloride the added sodium nearly disappears, and the water gains about 203 mg/L of potassium instead. If only one person in the home is on a sodium-restricted diet, an unsoftened kitchen tap does the same job for drinking water at no extra running cost.
Frequently asked questions
Can I mix potassium chloride and salt in my softener?
Yes. Morton says the two can be mixed in any ratio, and you don’t need to empty the tank to switch.
Is potassium chloride better for a water softener?
It’s better for keeping sodium out of your water and slightly lowers chloride discharge. It isn’t better at softening: it’s less efficient and costs more.
Do I need to change settings for potassium chloride?
Check the manual for a dedicated setting or dose. Test the softened water after switching to make sure it stays near zero hardness.
Does potassium chloride come in blocks?
Morton sells it only as pellets.
Is potassium-softened water safe to drink?
For healthy people, yes, according to Morton. People with certain medical conditions should ask their doctor first.
