Softener, filter, or RO?
Different jobs. Don’t buy one system hoping it does all three. Start with a compare, then go deep on one type.
At a glance
Which system solves which problem
No single box does it all. Find your problem on the left, then read across — the green check marks the system built for that job.
| Your problem | Softener Whole-home scale | Filter Taste · chlorine | RO Drinking water | Well Well · iron |
|---|---|---|---|---|
| Scale · hardness Whole-home anti-scale | Softens all | Kitchen only | ||
| Taste · odor Chlorine · sulfur | Carbon | Kitchen only | Sulfur only | |
| Drinking water Safe at the tap | Softens only | Not a purifier | Bottle-grade | |
| Iron · manganese Rust · well water | Trace only | Rust bits | Overkill | Oxidation |
| Whole-home Every tap | Sink only |
- Softener Softens all
- Filter
- RO Kitchen only
- Well
- Softener
- Filter Carbon
- RO Kitchen only
- Well Sulfur only
- Softener Softens only
- Filter Not a purifier
- RO Bottle-grade
- Well
- Softener Trace only
- Filter Rust bits
- RO Overkill
- Well Oxidation
- Softener
- Filter
- RO Sink only
- Well
Not in the table: RO makes waste water (concentrate) for every gallon it produces, and a softener uses salt with a brine discharge each regen. Details live in each system's guides.
Compare
Pick by the problem, not a brand
Side-by-side guides for the big forks: softener vs RO vs filter, and salt vs salt-free.
Water Softener vs RO vs Water Filter (Which Do You Need)
Softener removes hardness minerals, RO removes dissolved solids for drinking, whole-house filter removes sediment and chlorine. Here is how to choose.
Compare systems
Salt vs Salt-Free Water Softener (Which Is Right for You)
Salt-based softeners remove hardness via ion exchange. Salt-free conditioners crystallize minerals so they don't scale, but your strip still reads hard.
Read comparisonBy system
Learn one system at a time
Softener, whole-house filter, RO, and well—each with its own deep guides. Open Read more for the full set.
Softener
Water softener
Hardness scale and ion exchange—what the tank is doing.
How Water Softeners Work (Ion Exchange and Brine)
Ion exchange, the five-stage regeneration cycle, metered vs timer heads, and what a softener does NOT remove—explained without brand sales talk.
How it works Salt vs Salt-Free Water Softener (Which Is Right for You)
Salt-based softeners remove hardness via ion exchange. Salt-free conditioners crystallize minerals so they don't scale, but your strip still reads hard.
Read comparisonComing soon
Softener vs water conditioner
Marketing names vs what actually removes hardness grains.
Filter
Whole-house filter
Sediment and carbon—taste, chlorine, dirt. Not the same as soft.
Whole-House Water Filters: When You Need One
Whole-house filters remove sediment and chlorine at the main line, not hardness. Learn what they do, when to skip, and how they differ from a softener.
Filter guideComing soon
Whole-house filter vs softener
Taste/chlorine vs scale—when you need one, the other, or both.
Coming soon
Carbon vs sediment whole-house filters
Which cartridge job you actually need at the main line.
RO
RO (point-of-use)
Under-sink drinking and cooking polish—not every shower.
Reverse Osmosis Under the Sink: How It Works, When You Need
Under-sink RO removes dissolved solids, lead, arsenic, and most contaminants. NSF/ANSI 58 systems are the standard. Hardness needs a softener.
RO guideComing soon
RO vs softener (homeowner view)
Drinking water vs whole-house hardness—different jobs.
Coming soon
Tankless vs tank RO
Space, flow, and when a tankless unit is worth it.
Well
Well & iron
Iron and well-specific treatment—not municipal hardness alone.
Well Water Iron Filters: What to Know Before You Buy
Iron in well water stains fixtures and clothes. Air-injection filters, manganese greensand, and softener+iron combos compared by iron level.
Iron guideComing soon
Well treatment order
Iron, sediment, softener—what sequence actually works.
Coming soon
Well vs city water treatment
What changes when you’re on a private well instead of municipal.
Next steps outside Systems
Choose gear, fix a failure, size the tank, or read the hardness number.