Sodium in Softened Water
A common worry about softeners is that they make water "salty" or unhealthy. They don't make it taste salty, but they do add some sodium — and exactly how much depends on how hard your water was to begin with. Here's how to estimate the amount for your own water, how it stacks up against the sodium in food, and what to do if you need to keep it low.
Why softening adds sodium at all
A softener works by ion exchange: as hard water passes through the resin, calcium and magnesium ions stick to the beads and an equivalent amount of sodium is released into the water. So the sodium added is directly proportional to the hardness removed — the harder your water, the more sodium ends up in it. Nothing else about the water changes, and the sodium is present as dissolved ions, not as table salt, which is why softened water doesn't taste salty at normal hardness levels.
How much, in numbers
The standard figure is about 7.5 mg of sodium per liter for every grain per gallon (GPG) of hardness removed — roughly 0.44 mg per liter for each 1 PPM. You can estimate your own water from its hardness. The table below assumes all of your hardness is softened out, and an 8-ounce glass is about 0.24 liter:
| Hardness | Sodium added (per liter) | Per 8 oz glass |
|---|---|---|
| 5 GPG (86 PPM) | ~38 mg | ~9 mg |
| 10 GPG (171 PPM) | ~75 mg | ~18 mg |
| 15 GPG (257 PPM) | ~113 mg | ~27 mg |
| 20 GPG (342 PPM) | ~150 mg | ~36 mg |
| 30 GPG (513 PPM) | ~225 mg | ~53 mg |
You can read your compensated hardness straight off the calculator, or brush up on GPG versus PPM if your report uses different units.
How that compares to your diet
For context, general dietary guidance puts a day's sodium ceiling around 2,300 mg for most adults, and the large majority of that comes from food, not water. The U.S. Food and Drug Administration considers bottled water "very low sodium" below about 35 mg per 240 mL and "low sodium" below about 140 mg per 240 mL. At moderate hardness, a glass of softened water sits in the low range and is a minor contributor. It's at very hard water combined with a strict sodium restriction that the numbers start to matter — someone drinking two liters a day of water softened from 25–30 GPG could take in a few hundred milligrams of sodium from water alone.
Who should be cautious
If you're on a physician-ordered low-sodium diet — for high blood pressure, heart failure, or kidney disease, for example — it's worth accounting for softened water and mentioning it to your doctor. The same goes for water used to mix infant formula. This is general information, not medical advice; your own limits and water hardness are what matter, so check your water report and talk to a healthcare professional if you're unsure.
Your options if you want to keep sodium low
- Leave a hard-water tap. The most common approach is to plumb the kitchen cold tap (and outdoor spigots) with unsoftened water, so drinking, cooking, and the garden get the original water while the rest of the house gets soft water.
- Add reverse osmosis for drinking water. A small under-sink RO unit removes most of the added sodium along with other dissolved solids, giving you low-sodium drinking water while keeping soft water everywhere else.
- Use potassium chloride instead of salt. Running potassium chloride in the brine tank adds potassium rather than sodium. It costs more and is a little less efficient, and people with kidney disease or on potassium-sensitive medication should check with a doctor first, but it sidesteps the sodium question entirely.
A note on plants and aquariums
Softened water isn't ideal for houseplants, gardens, or fish tanks — the added sodium can build up in soil and stress many plants. If you soften the whole house, use an unsoftened outdoor spigot for the garden and think twice before topping up an aquarium with it.
Related guides
Still weighing whether softening is right for you? See do I need a water softener?, compare salts in the salt guide, or check the FAQ for quick answers.