Whole-House System
Kenmore 420 Water Softener (40,000-grain)
Certification on record for this guide’s contaminants
- Hardness: certified
Buying guide · water softeners
How a Water Softener Works
Prevents most scale. It doesn’t treat lead, PFAS or germs.
A water softener swaps the calcium and magnesium that make water hard for a small amount of sodium (or potassium). That stops crusty scale on faucets, spots on dishes and buildup in your water heater. It doesn’t make water safer to drink: it’s about comfort and appliance life.
How it works, step by step
Hardness out, a little sodium in
Ion exchange in a resin tank, recharged with salty water from a brine tank.
Built for hardness, not lead, PFAS, chlorine or germs. For those, use a filter certified for them at the tap you drink from.
- Hard waterHard water flows into a tank full of tiny resin beads. The beads hold sodium.
- Ion exchangeMain stageCalcium and magnesium stick to the beads, and the beads let go of sodium in exchange.
- Soft water outSoft water flows on to your taps.
- RegenerationRechargesEvery few days the beads fill up. The softener rinses them with salty water from the brine tank, which washes the hardness down the drain and recharges the beads.
- Brine tankYou keep the brine tank topped up with softener salt.
Signs you need one
Worth it when scale and spots bother you
Hard water isn’t a health risk. A softener is worth it when scale and spots bother you, or to protect a water heater and appliances.
You see
White crust
On faucets and shower heads
You see
Spots
On glasses and dishes, even after the dishwasher
You see
Poor lather
Soap and shampoo that won’t lather well
The number
7+ gpg
A water report or test strip showing 7 grains per gallon or more
Choosing the right sizeSofteners are rated in grains: how much hardness they remove before they recharge. A common rule of thumb for your daily load: multiply the people in your home by about 75 gallons a day, then by your hardness in grains per gallon. We size for a weekly recharge at efficient salt settings, which get roughly half to two-thirds of the rated grains; we size with half.
People × 75 gallons × your hardness
People in your home
3From your water record or a test strip25 gpg
Daily load2,250 grains
Look for · rule of thumb32,000-grain
Assumes a weekly recharge at efficient salt settings, which get roughly half to two-thirds of the rated grains; we size with half.
Salt, sodium and costs
The running cost is mostly salt
- Salt
- One or two bags a month in most homes
- Refill
- Every 4–8 weeks
- Sodium added
- A little; more if very hard
- Install
- Add a plumber if you don’t do it yourself
Limiting sodium? A softener adds a little sodium to your water, more if your water is very hard. Ask your doctor, use potassium chloride instead of salt, or keep one unsoftened tap for drinking.
Good for
- Hard or very hard water (7 grains per gallon or more)
- Scale on fixtures and spots on dishes
- Protecting a water heater and appliances
Not the right fit for
- Lead, PFAS or germs→ it isn’t built for them
- Low-sodium diets→ potassium salt or an unsoftened drinking tap
- Most renters→ ask your landlord
Before you buy, check what is in your water. Your water system’s record shows which contaminants have been found, so you only pay for treatment you need.
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Water softeners we track
Each card shows whether the model is certified for hardness reduction. Open a product to see its certificate. Some links are affiliate links: PurityMap may earn from qualifying purchases, at no extra cost to you.
Whole-House System
GE GXSH35W Water Softener (35,000-grain)
Certification on record for this guide’s contaminants
- Hardness: certified
Every product here is listed for its type and what its certification covers, not for what is in your water. We don’t accept paid placement. Affiliate disclosure.
Questions
Common questions
Does a water softener make water safer to drink?
No. It’s built for hardness, not for lead, PFAS or germs. Some models are also certified for barium or radium; see the certificate. If lead or PFAS worry you, add a certified drinking-water filter.
Salt-based or salt-free?
A salt-based softener removes hardness. A salt-free conditioner only changes how the minerals behave, so it reduces scale but the water still feels hard.
How long does a softener last?
Often 10–15 years with care. The resin may need replacing sooner if your water has a lot of chlorine or iron.