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 comparison
Water Softener vs Water Conditioner (Honest Comparison)
Salt-based softeners remove hardness via ion exchange. Salt-free conditioners don't reduce it, but they do prevent scale. Here's how to pick.
Read guide
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 guide
Whole-House Filter vs Water Softener (What Each One Does)
A whole-house filter catches sediment and chlorine. A softener removes calcium and magnesium. Here is what each does, and why the filter goes first.
Read guide
Whole-House Carbon Filter vs Sediment Filter: Which First
Compare whole-house carbon and sediment filters on precision, media, series order, maintenance, and which one to install first.
Read guide
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 guide
Reverse Osmosis vs Water Softener: Which Do You Need?
Compare what RO and water softeners remove, point-of-use versus whole-house coverage, wastewater, installation, upkeep, and when you may need both.
Read guideComing 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 guide
Well Water Treatment Order: Right Sequence
Test well water first, then treat in order: sediment, oxidize iron/sulfur, filter, soften, disinfect. Decision tree plus four household cases.
Read guide
Well Water vs City Water Treatment: What Changes
Well vs city water treatment differs by who treats the source, what you test first, and which gear belongs on each path.
Read guideNext steps outside Systems
Choose gear, fix a failure, size the tank, or read the hardness number.