Water Treatment
Softeners, reverse osmosis and the question of whether you need either, with every figure sourced and, unusually for this subject, with the source behind the source named.
This section opened on 30 October 2026. It works the way the rest of the site does: every figure names the guide it came from and the date that guide was updated, and where sources disagree we show the disagreement instead of splitting the difference.
One thing is different here, and it shaped how these pages are written. In water treatment, two cost guides quoting an identical range usually turn out to be quoting the same upstream dataset rather than confirming each other. We found it on softeners and again on reverse osmosis, and in both cases one of the two publishers says so on the page if you read the small print. So on this subject we name not just the guide but, where it is stated, where that guide got its numbers.
The six questions so far
| Page | The short answer | What it adds |
|---|---|---|
| Do I need a water softener? | a $10 test decides it, not the symptoms | the GPG threshold and the three ways to measure, and why hard water lands in the water heater rather than the cold pipe |
| Water softener cost | about $1,100 to $3,000 for a whole house | two publishers print an identical range and one of them states in a footnote that the data came from Angi |
| Reverse osmosis cost | $150 to $1,300 at one tap, $1,000 to $4,800 for the house | the same identical-range pattern, attributed here to HomeAdvisor, and why the point-of-use choice is worth more than the brand |
| Softener vs filter | not alternatives, they solve different problems | three rows on one publisher's page that will not reconcile, and why "conditioner" tells you nothing |
| What regeneration is | the salt cleans the resin, it does not soften the water | why a metered unit beats a timer, and why a single-tank softener has two tanks |
| What it costs to maintain | $310 to $620 a year on one publisher's own items | a salt figure that does not match the bag price in the same sentence, and two maintenance numbers covering different periods |
Where the numbers come from
Three published guides carry this section so far: Fixr's water softener installation guide, This Old House's water softener system cost guide, and This Old House's and Bob Vila's reverse osmosis guides. Fixr is the only one of them that builds its own ranges from pricing databases and contractors; the others reprint figures from Angi and HomeAdvisor, which are lead-generation platforms rather than publishers. We say which is which on every page, because on this subject it changes how much weight a number deserves.
What connects this to the rest of the site
Hard water does its most expensive damage inside a tank water heater, where the minerals come out of solution as the water is heated. If you arrived here from our water heater section, the softener question is part of the same bill.
Questions answered
- Do I need a water softener?Updated 2026-10-30This Old House's water softener guide (updated June 16, 2026) says water hardness is measured in grains per gallon, that the GPG figure runs from 0 to 20, and that anything at seven or above is considered hard water. You can buy a test kit from a retailer for about $10, get a free test from a local water treatment company, or check your water utility's annual reports. Fixr's guide (updated January 31, 2025) lists the symptoms that should prompt the test: film on sinks and dishes, stains on the showerhead, soap that will not lather, stiff laundry, dry skin, falling water pressure and appliances that fail early.
- How much does a reverse osmosis system cost?Updated 2026-10-30This Old House's reverse osmosis guide (updated March 30, 2026) gives an average of $2,475 across a range of $150 to $4,800. Bob Vila's whole-house guide (updated February 29, 2024) gives the identical $150 to $4,800 range, attributed to HomeAdvisor, with an average of $2,200. Both split it the same way: a point-of-use system under one sink runs $150 to $1,300, while a whole-house point-of-entry system runs $1,000 to $4,800 or more. That split, not the brand, is what decides your price.
- How much does a water softener cost?Updated 2026-10-30Fixr's water softener guide (updated January 31, 2025) puts installation at $1,100 to $3,000 with an average of $2,500 for a dual-tank ion exchange system in a 3 to 4-bedroom home. This Old House (updated June 16, 2026) gives $200 to $6,000 with an average of $3,100, and notes in its own table that the cost data was sourced from Angi. Bob Vila (updated April 22, 2024) gives the identical $200 to $6,000 range with an average of $1,500, citing HomeAdvisor and Angi. So two of the three are not independent confirmation of each other, and the honest working figure for a standard whole-house system is Fixr's $1,100 to $3,000.
- What does a water softener cost to maintain?Updated 2026-10-31This Old House's water softener guide (updated June 16, 2026) itemises the running costs: salt at $5 to $10 a month, water filters at $20 to $50 each, cleaning the resin tank at $100 to $200 annually, and annual professional servicing at $150 to $300 covering cleaning, performance testing and minor repairs. Fixr's guide (updated January 31, 2025) gives an average of $150 to $600 for water softener maintenance, and says ion exchange and reverse osmosis systems need routine inspections every two or three years. The two figures look similar but cover different periods.
- What is water softener regeneration?Updated 2026-10-31Regeneration is how a water softener cleans itself out. This Old House's guide (updated June 16, 2026) describes the mechanism: sodium-coated resin beads carry a charge opposite to the mineral ions in the water, the ions swap places, and once the beads are saturated a brine solution runs through to release the hardness minerals to drain and recharge the resin. Grain capacity is how much hardness a system removes before it has to do this. Fixr's guide (updated January 31, 2025) adds that the salt or potassium chloride goes into a separate brine tank, which is why even a single-tank softener actually has two tanks.
- Water softener vs water filter: which do you need?Updated 2026-10-31A softener removes the calcium and magnesium that cause limescale. A filter removes other things: sediment, chlorine, bacteria, dissolved solids. Fixr's guide (updated January 31, 2025) prices a softener at $1,100 to $3,000 and a full water treatment system, which is a softener plus a filter, at $2,100 to $3,300, with a whole-house filter and softener combination running $1,500 to $10,000. This Old House's reverse osmosis guide (updated March 30, 2026) quotes an expert on where the filter types divide: reverse osmosis does everything a carbon system does and also removes dissolved solids.