Water Filter vs Water Softener: What's the Difference?
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A water filter removes contaminants like iron, sediment, chlorine, bacteria, and chemicals. A water softener removes hardness minerals (calcium and magnesium) that cause scale buildup, spotted dishes, and dry skin. One cannot replace the other. So no, a softener is not the same as a filter, and the number one mistake I see is buying a softener and thinking it will fix every problem in the water.
A caller in Nevada had it the other way around. Her house already had a softener, the water was still leaving white spots on the dishes, and she was looking at our Katalox Light iron filter to fix it. I told her: "the Katalox Light system doesn't remove hard water. It actually makes the water harder." White buildup is hardness, and only a softener takes it out. Iron stains reddish orange and manganese stains gray, and those are a filter's job. The first step was to get her hardness checked in grains per gallon.
Quick Answer
No. A water softener takes the hardness (calcium and magnesium) out of your water, and a water filter takes out something else, such as chlorine, iron, sediment or a smell, depending on what is inside the tank.
- A softener does one job. Resin beads trade the hardness for sodium, and salt recharges them. Chlorine, sediment, the rotten egg smell and bacteria go straight through, and it takes only a little iron. Our single-tank softeners are $1,495 to $2,495. See how a softener works.
- "Water filter" covers many tanks. A carbon tank for chlorine and taste, an iron filter for iron and the rotten egg smell, an acid neutralizer for low pH, a sediment cartridge for sand. None of them soften. See five kinds of water filter.
- Your test decides. Above 7 grains per gallon of hardness, you need a softener. Iron, a smell, low pH, chlorine or sediment each need their own filter. See which one your water needs.
- Most of my customers end up with both. The filters that protect the softener go in ahead of it: carbon on city water, sediment and iron filters on a well. Our filter and softener packages start at $3,095. See when you need both.
- One tank or two. Our one-tank carbon filter and softener ($2,195) is for one or two people with low water use. Families do better with two tanks. See one tank or two.
What's in This Guide
Filter vs softener side by side
People ask me if a filter can do what a softener does, and the other way around. The answer is no: each one takes out things the other leaves in.
| Water filter | Water softener | |
|---|---|---|
| Takes out | Depends on what is inside: chlorine and bad taste (carbon), iron, manganese and the rotten egg smell (iron filter), sand and silt (sediment cartridge) | Hardness: the calcium and magnesium that leave scale and white spots |
| What stays in the water | Hardness | Chlorine, sediment, the rotten egg smell, bacteria and low pH. It takes only a little iron. |
| How it works | The water runs through media picked for one problem | Resin beads trade the hardness for sodium, and a salt rinse recharges them |
| What you add | A new cartridge, new carbon every few years, or more calcite, by kind | Salt |
| Needs a drain or outlet | Not a cartridge or our non-backwashing tanks. An iron filter needs a drain and an outlet. | A 1/2 inch drain line and an outlet |
| Our prices | $165 for a sediment housing to $3,295 for a large-home iron filter | $1,495 to $2,495 for a single tank |
I made a short video on exactly this question, with a carbon tank and a softener side by side.
How a softener works
No, a water softener does not filter water. A softener takes out only the calcium and magnesium. Everything else in your water goes right through it. A softener is two tanks: a tall resin tank with the control valve on top, and a salt tank beside it. The resin tank is full of tiny resin beads with a charge on them. They hold onto the hardness as the water passes, and when they are full, the valve rinses them with salt water from the salt tank to recharge them. The valve does that on its own, at night, based on how much water you have used.
A softener takes a little iron, but iron shortens the life of the resin, and sediment can clog the resin bed and can't be backwashed out. That is why a filter goes in front of a softener whenever the water has either one. Every softener we sell uses 10% crosslink resin; kept away from iron and chlorine, it has lasted 30 to 40 years in my service work. To size one for your house, see what size water softener you need, and for the parts and the nightly cycle in detail, see how a water softener works.
Five kinds of water filter
A water filter is any tank or cartridge built to take one kind of problem out of the water, and which one you need depends on what is in yours. These are the five kinds we sell. None of them softens the water.
| Filter | What it takes out | Drain or power | Our price |
|---|---|---|---|
| Sediment cartridge (Big Blue) | Sand, silt and grit, before they reach the tanks after it | No drain, no outlet | $165 (10 inch) or $195 (20 inch) |
| Carbon tank | Chlorine, bad taste and smell. It also reduces chlorine byproducts, herbicides and pesticides. | No drain, no outlet (non-backwashing) | $1,495 or $1,695 (non-backwashing) |
| Iron filter (Katalox Light) | Iron, manganese and the rotten egg smell | A drain and an outlet. It backwashes itself. | $2,095 to $3,295 |
| Acid neutralizer | Nothing. Its calcite raises the pH of acidic water. | No drain, no outlet (non-backwashing) | $1,195 to $1,695 |
| UV light | Nothing. It kills bacteria as the water passes the lamp. | An outlet, with a 5 micron sediment cartridge ahead of it | $895 or $995 |
Two of them make the water harder. The calcite in an acid neutralizer adds about 3 to 6 grains per gallon of hardness as it dissolves; one buyer on a well wrote that his neutralizer "did change my water to hard," to "about 8.7g/Gal.," so he added a softener after it. And the Katalox Light in our iron filters, as I told the caller in Nevada, "actually makes the water harder." That is why a softener so often follows one of these two. Each kind has its own guide: iron filters, carbon filters, sediment filters and UV lights.
Which one your water needs
Test your water before you buy either one: the hardness number says whether you need a softener, and the rest of the test says which filter. Above 7 grains per gallon of hardness, a softener is what you need. Find your row:
| What you see or what your test shows | What you need |
|---|---|
| White scale, spots on the dishes, soap scum. Hardness above 7 grains per gallon. | A softener. See our water softeners. From about 3.5 to 7 grains a softener is optional; under 3.5 the water is soft. |
| Reddish orange stains (iron) or gray stains (manganese) | An iron filter. A softener alone takes only a little iron; see can a water softener remove iron. |
| A rotten egg smell on a well | A light smell: the 2.5 cubic foot carbon tank. A strong one: an iron filter. A softener does not take it out; see does a water softener remove sulfur smell. |
| Chlorine taste or smell on city water | A carbon tank, ahead of the softener if the water is also hard |
| Sand or grit, or a cartridge that clogs | A sediment cartridge right after the pressure tank |
| On a well: low pH on the test, or blue-green stains | An acid neutralizer, then a softener if the calcite takes the hardness over 7 grains |
| Bacteria on the test | A UV light, last in line |
| No water test yet | Well water: our $199 well water test checks 53 contaminants, lab fees included. City water: your water company's yearly report gives the hardness, or use our $99 hardness test. How to read it: how to test water hardness. |
Text Aidan your test results
Send your hardness, or your full lab report if you are on a well. He'll text back whether you need a filter, a softener or both, and which one goes first.
8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.When you need both
When your water is hard and has another problem too, you need a filter and a softener, and the filter that protects the softener goes in ahead of it. Most of my customers end up with both. City water usually brings chlorine and hardness together. A well can bring low pH, iron, a sulfur smell, manganese or bacteria on top of the hardness. The softener takes care of the hardness only, so each of the other problems gets its own tank in front of it.
The order is there to protect the softener. I tell people it's like a football team: "your pre-filter, your iron filter, your sediment filter, they're your blockers and your quarterback is your water softener. That's who you want to protect."
Which one goes first
City water: the carbon tank first, then the softener, so the chlorine is gone before the water reaches the resin. A caller in Texas this month, on city water that is "a little bit" hard, asked if our Big Blue sediment filter should go before his softener. On city water the filter that goes first is carbon, I told him: "City water's pretty basic. You just put the carbon filter in and the softener, and you're good to go." The details are in carbon filter and water softener.
Well water: a sediment cartridge right after the pressure tank, then the iron filter or acid neutralizer, then the softener. A carbon tank, if you need one, goes after the softener, and a UV light goes last. When a well needs both an iron filter and a neutralizer, I set their order from your test. For a family of five on a well with iron and hard water this month, it was out of the pressure tank into a 2.5 cubic foot Katalox Light filter, then a 64,000 grain softener "because you have five people," then a nitrate filter for the nitrates on their test. Every stage is in the correct order for well water treatment.
We sell the common pairs as packages, and each one costs less than the two tanks bought separately:
| Your water | What we sell | Price |
|---|---|---|
| Well: iron or a sulfur smell, and hardness | Iron filter and softener packages | From $3,395 |
| Well: low pH and hardness | Acid neutralizer and softener packages | From $3,095 |
| City: chlorine and hardness | Carbon filter and softener packages | From $3,195 |
One tank or two
We sell one tank that does both: the All In One carbon filter and water softener, $2,195. It is a 2.5 cubic foot tank with two chambers, carbon on top and softener resin below, with a plate in the middle that keeps them apart, plus its own salt tank. The one-tank unit is for low water use, one or two people in a smaller house, and for a family, two tanks are the better buy.
A caller pricing it for a house of five people and three and a half baths got that answer from me: "the all-in-one's for, like, low water usage," and "The majority of our customers go with the dual tank system," meaning a separate carbon tank and softener. The reason is room. Sharing one tank, the softener side "only has, uh, forty-eight thousand in the bottom," and a big household uses up the carbon sooner. With two tanks, "Each tank holds its own type of media," and for five people, "it's better to have greater capacity." Because the one tank pairs carbon with a softener, it is for chlorine or a bad taste plus hardness. A well with low pH, or more iron than a softener handles, needs its own filter in front.
What comes in the boxes
Every tank ships empty, with its media in separate bags or boxes that go into the tank at install; a full tank is too heavy to ship. The question I get most after delivery is the one a caller asked for her husband in September: "I know that the tanks came empty, so he wanted to know if you had, like, either a diagram or, uh, directions, like what bag goes in what tank in what order." The resin goes in the softener tank, and the filter media goes in the filter tank.
- The softener: the Fleck 5600SXT valve with its bypass valve already on it, an empty Vortech tank, the salt tank, and the resin in bags.
- The filter: its valve or head, an empty Vortech tank, and its media in bags or boxes. A sediment cartridge ships in its housing.
- Not in the boxes: the 1/2 inch drain tubing for the softener and any backwashing filter (any hardware store has it), the pipe and fittings, and the salt.
The makers put little or no install guidance in the box, so use how to install a water softener, and call or text me with questions.
Who installs them
I recommend having a plumber put them in, ideally one who has installed water treatment before, and I'm a phone call away for your plumber. A filter and a softener are two tanks in a set order, and each backwashing tank needs its own drain line, so plan on 3 to 4 hours of a plumber's time for the pair. A softener on its own is about 2 to 3 hours, about $800. If you'd rather do it yourself, text me with any questions.
What each one costs to run
The softener's running cost is salt. The filters each need something different, on their own schedule:
| Tank | What you add | How often | Cost |
|---|---|---|---|
| Softener | Pellet salt | About a 40 lb bag a month. In my house it's one every 30 to 45 days. | About $8 a bag |
| Sediment cartridge | A new cartridge | When the water pressure drops, usually every 4 to 6 months | $55 (20 inch) |
| Carbon tank | New carbon | About every 5 years | $295 per cubic foot |
| Iron filter | Nothing yearly. It backwashes itself. | New Katalox Light every 6 to 8 years | $325 per cubic foot |
| Acid neutralizer | More calcite, the mineral that raises the pH | When the tank is about halfway down. Check it once a year. | $145 per 50 lb box |
| UV light | A new lamp | Every 12 months | $165 or $170 |
Frequently asked questions
Do water softener systems have filters?
Not a filter that catches dirt. A softener is a resin tank and a salt tank, and the resin trades hardness for sodium while everything else goes through. On a well, I put a 20 inch Big Blue sediment cartridge in front of it, after the pressure tank, to keep sediment out of the softener's valve.
What does a water softener look like?
Two tanks side by side: a tall, narrow resin tank with the control valve and its little screen on top, and a shorter, wider salt tank beside it. On our 48,000 grain, the resin tank is 10 inches across and 54 inches tall, about 60 inches with the valve. A filter tank looks much the same but has no salt tank, which is the quick way to tell them apart.
What are the downsides of having a water softener?
You carry salt, about a 40 lb bag a month. It needs a drain and an outlet near where it goes. And it fixes hardness only: on a well with iron, a sulfur smell or low pH, a softener on its own "will not take care of it."
What is the best water conditioner?
A salt-free water conditioner stops scale, but it does not soften: the hardness stays in the water, and a test still reads hard. The one we recommend is our 2.5 cubic foot Filtersorb conditioner, $2,895, for a house with no drain, no outlet or no room for a salt tank. A buyer who had owned a salt softener before wrote that with his, "the water is not as soft as the water was when we had our salt water softener." See the best salt-free water softener.
Is a carbon filter necessary for a water softener?
No, a softener works without one. On city water I put a carbon tank in first anyway, because chlorine shortens the life of the resin. On a well with no chlorine, a carbon tank is there for taste and smell and to reduce herbicides and pesticides, and it goes after the softener.
What are the disadvantages of a whole house water filter?
The big one is buying the wrong kind, since each filter takes out one kind of problem; test first. Then the upkeep: cartridges clog and get changed, carbon wears out in about 5 years, and an iron filter needs a drain line and an outlet. And none of them soften the water.
Aidan Walsh
Co-owner & Residential Water Treatment Specialist, Mid Atlantic WaterAidan Walsh has spent 32 years in residential water treatment, the first stretch of it installing and servicing well systems before Mid Atlantic Water became an online supplier. Mid Atlantic Water is a family company; every recommendation on this site is based on what actually failed in the field and what fixed it. If you have a question this page did not answer, call 800-460-5810 or text him at 443-277-2204.
Aidan answers calls and texts 8 AM to 5 PM Eastern, every day.Number copied. Text it from your phone: 443-277-2204.