Cost guides

What the three main systems cost

Home water treatment splits into three purchases with very different price structures: a softener (equipment plus install, then salt forever), a whole-house filter (cheaper equipment, frequent cartridge changes), and reverse osmosis (low equipment cost, slow output, membrane and filter replacements). Comparing them on sticker price alone is the most common buying mistake.

System	Equipment	Installed	Running cost / year
Whole-house softener	$600–$2,500	$1,200–$4,500	$120–$400 (salt) + power
Whole-house carbon filter	$200–$900	$500–$1,800	$80–$300 (cartridges)
Under-sink reverse osmosis	$200–$600	$300–$900	$60–$150 (filters, membrane every 2–3 years)
Whole-house RO	$2,000–$6,000	$3,000–$8,000	$300–$700 + high water waste
Salt-free conditioner	$300–$1,200	$500–$1,800	$0–$100

Installation dominates the spread. A softener needs a drain, a power outlet, a bypass loop and a 3/4-inch supply; a house without those adds $300–$900 in plumbing before the unit goes in. An under-sink RO needs a dedicated faucet hole and a tank location, which is why the same $300 unit can cost $900 installed.

What the quote leaves out

• Permit and inspection where the municipality requires one for a water-line change.
• Bypass valve and shut-offs — often $80–$200 in parts, sometimes billed as "miscellaneous".
• Drain line and air gap for the softener regenerate; a floor drain within 15 feet is not universal.
• Electrical for a timer or metered head if there is no outlet at the install point.
• Old-unit removal and disposal, $50–$150 in most markets.
• First fill of salt, $40–$80, and the first set of filters.

First-year versus five-year cost

The cheapest installed price is rarely the cheapest system. A $1,200 softener with a 10-year resin life and $30 bags of salt costs less over five years than a $700 unit that regenerates every two days and needs a $200 control head at year three. Model it on consumables, not on the invoice:

Line	Cheap unit	Mid unit
Installed	$900	$2,200
Salt, 5 years	$1,000	$700
Service and parts, 5 years	$600	$250
Five-year total	$2,500	$3,150

Both columns are defensible: the cheap unit wins on cash, the mid unit wins on water quality and service calls. What is not defensible is comparing a five-year total for one system against an installed price for another. The softener cost guide carries the full arithmetic, and the systems hub explains what each unit actually removes.

Cost per gallon, the only fair comparison

Divide the five-year total by the gallons the household uses. A family of four at 80 gallons a day uses about 146,000 gallons in five years; a $3,150 system lands near 2.2 cents per gallon, a $2,500 system near 1.7 cents. That number — not the sticker — is what changes when you choose between a softener, a filter, or both.

Is a softener worth the money?

Where hardness is above about 7 grains per gallon, yes: soap, appliance life and scale in the water heater usually recover the cost within a few years. Below 5 grains, a filter is often the better spend.

Why do two quotes differ by $2,000?

Usually installation conditions: drain distance, electrical, permit, and whether the quote includes a bypass, old-unit removal and the first salt fill. Ask for a line-item quote, not a lump sum.

Do I need a softener and a filter?

Often yes, for different jobs. The softener removes hardness; the filter removes chlorine, sediment or taste. One unit that claims to do both is usually a filter with a marketing department.