Hard water carries dissolved calcium and magnesium. It is not a health concern, but it costs money: scale shortens the life of water heaters and dishwashers, clogs shower heads, spots glass and makes soap work poorly. The US Geological Survey calls water above 120 mg/L (7 grains per gallon) hard and above 180 mg/L (10.5 gpg) very hard.
The one thing a filter can't do
Carbon filters, pitchers and shower filters reduce chlorine, taste and some contaminants. They do not remove hardness minerals in any meaningful amount, whatever the packaging suggests. Reverse osmosis does remove them, but only for drinking water at one tap.
Your three real options
- Salt-based (ion exchange) softener. The only whole-home option that removes hardness. Needs a drain, an outlet and bags of salt. Typical installed cost: $1,000-3,000. Best for owners with very hard water.
- Salt-free conditioner (TAC). Template-assisted crystallization changes minerals so they are less likely to form scale. Minerals stay in the water, so you still get spotting, but scale buildup drops. No salt, no drain.
- Point-of-use scale inhibitors for renters: small cartridges under a sink or on an appliance line that slow scale where it matters most.
Sizing a softener
Multiply your hardness in grains per gallon by your household's daily water use (about 75 gallons per person). A family of four at 15 gpg needs about 4,500 grains a day; a 32,000 to 48,000-grain unit regenerates every week or so. Get two or three installer quotes: plumbing, drain access and local codes change the price more than the unit does.