They solve different problems. A softener changes the water in your whole house. Reverse osmosis changes the water in your glass. Here is how to tell which one your water calls for.
People ask for a water softener when they mean “make my water better.” Those are not the same purchase. A softener and a reverse osmosis system fix different problems, in different parts of the house, at very different prices.
The one-line difference
A softener treats the whole house and removes hardness. It swaps calcium and magnesium for a small amount of sodium, using resin beads that recharge with brine. Every tap, shower and appliance gets softened water.
Reverse osmosis treats one tap and removes almost everything. It pushes water through a membrane fine enough to hold back most dissolved solids, then polishes the taste with carbon. It lives under the kitchen sink and feeds its own faucet.
| Water softener | Reverse osmosis | |
|---|---|---|
| Where it works | Whole house | One faucet (usually the kitchen) |
| What it removes | Hardness: calcium and magnesium | Most dissolved solids, including lead and PFAS |
| What it does not remove | Chlorine, chloramine, taste and odor | Nothing at your shower or appliances |
| What you notice | No more scale or spotting, soap rinses cleaner | Water and ice taste clean, no more jugs |
| Our guarantee target | Under 1 grain per gallon | 85% or more less TDS than your tap |
Pick by the complaint, not the product
“There’s crust on the shower head. The glasses come out spotty.” That is hardness. A softener is the only one of the two that changes it, because scale is calcium and magnesium drying on a surface. See do I need a water softener for the hardness numbers by city.
“It smells like a pool. The water tastes like chlorine.” Neither product is the right first answer. That is the disinfectant, and on most of the Front Range it is chloramine, which needs catalytic carbon. Whole-home carbon fixes it at every tap and shower; RO fixes it at one faucet.
“We buy jugs and pitchers. The coffee tastes off.” Reverse osmosis, and it is the cheapest way in. You are paying to change one tap, not the house.
“Nobody has ever tested our well.” Start with a certified lab test. Wells can carry iron, sulfur, bacteria, nitrate, arsenic or uranium, and the treatment order depends entirely on what comes back. A softener or an RO faucet might both end up in the design, but they are the last decisions, not the first.
Why hard-water homes usually end up with both
On the hard chloramine cities, Thornton, Aurora, Westminster and Castle Rock, the complaint list is almost always both scale and taste. That is the case for a complete system, in this order:
- Sediment prefilter to protect everything downstream.
- Catalytic carbon to take out chlorine and chloramine, which also protects the softener resin.
- Softener to remove the hardness.
- Reverse osmosis at the kitchen sink for drinking and cooking water.
Order matters. Carbon goes before the softener, not after, because chloramine shortens resin life. You can see the whole chain in how it works.
What each one costs to keep running
- Softener: salt, and not much else. A metered valve only regenerates when it has used its capacity. Resin lasts years; the valve is rebuildable.
- Reverse osmosis: filter cartridges on a schedule, and a membrane every few years. The cartridges are the recurring cost, and we publish what they are before you buy.
Still not sure?
Look at the complaint, then the number. If you want the number for your own house, we will measure hardness, total chlorine and TDS at your tap, write down the target the system has to hit, and tell you if you do not need one of these at all.
Sources
- Hardness and disinfectant by city, with each utility's own source — our summary of the published figures
- City of Thornton: water hardness made easy — about 200 mg/L average, used in the sodium calculation
Common questions
Can I have both a softener and reverse osmosis?
Yes, and it is the most common setup on hard Front Range water. The softener protects the whole house from scale, and the RO faucet gives you drinking and cooking water with most of the dissolved solids removed, including the sodium the softener added.
Does reverse osmosis remove hardness?
At the faucet it does, because the membrane holds back most dissolved minerals. But an under-sink RO system only treats one tap. It does nothing for your shower head, dishwasher or water heater.
Does a softener clean up the taste?
Not really. Ion exchange swaps calcium and magnesium for sodium. It does not remove chlorine, chloramine or most other taste and odor compounds. That is a carbon filter's job.
If I only want one, which should I get first?
Pick by the complaint. Scale, spotting and stiff laundry point to the softener. Taste, smell and buying bottled water point to reverse osmosis, which is also the cheaper place to start.