How much sodium is added to the water by the softener?"
That depends on the hardness of the original water. This table shows the additional amount of sodium consumed by drinking one quart ( 4 - 8 oz. glasses per day ) of softened water.
Initial Hardness Sodium Added
1.0 grains per gallon 7.5 milligrams/quart
5.0 grains per gallon 37.5 milligrams/quart
10.0 grains per gallon 75.0 milligrams/quart
20.0 grains per gallon 150.0 milligrams/quart
40.0 grains per gallon 300.0 milligrams/quart
As a comparison, one slice of white bread has 161 milligrams of sodium; 3/4 cup of canned baked beans = 1130 milligrams; 1 tablespoon of catsup = 204 milligrams; 1 medium frankfurter = 610 milligrams; and 1 cup of whole milk = 127 milligrams. Even a common Alka Seltzer tablet contains 532 milligrams of sodium.
"Do I have to use salt to have soft water?"
No. You can use the salt substitute ( potassium chloride ). This is about 90% as effective as the regular salt ( you need to use about 10% more to get the same level of "recharging" capacity from your water softener ), AND it adds potassium instead of sodium. Another major downside is that potassium chloride costs between 3 and 4 times more than the regular softener salt.
So, the small amount of sodium added to your home's water is not normally going to be an "issue".
And if you are on a Strict Low Sodium diet ( 1500 mg per day or less ) and do plan on drinking 4 - 8 glasses of water per day, you should use Distilled water, or Reverse Osmosis water for all your drinking and cooking.
Don't neglect treating your house plumbing with a water softener,
BECAUSE having a hard water problem is damaging to your plumbing, your hot water tank, your dishes, appliances, clothes and your skin. The most immediate way to tell if you are experiencing a hard water problem is by noticing white spots on your kitchen faucet or bathroom faucets or dishware. Are your hands rough or constantly scaly? Any signs such as these are a definite hard water problem.
What Makes Water Hard?
Calcium and magnesium are the hardness minerals.
A water softener removes the hardness minerals, calcium and magnesium, from your water. When water with these hardness minerals passes through the water softener, the calcium and magnesium ions are attracted to resin beads inside the softener. In turn, the resin beads release sodium ions. Water without the hardness minerals is "soft."
For Sodium free drinking water a Reverse Osmosis Drinking water system can be used to remove the salts and other dissolved solids from the softened water before you drink it.
Average Salt Amount Needed and Normal Water Level In Brine Tank