Phoenix Hard Water Guide

What size water softener do you need in Arizona?

Softener size is about capacity, in grains: how much hardness it can remove before it has to recharge. In very hard Valley water, the right size depends on your city and how many people live with you.

Water softener size chart for Phoenix-area cities

Grain capacity by household size, with days between recharges and 40 lb bags of salt a year. Based on 75 gallons per person per day and each city's published hardness.

City or area1 person2 people3 people4 people5 people6 people
Phoenix13.8 grains per gallon24k14 days · 3 bags24k11 days · 6 bags24k7 days · 9 bags32k7 days · 12 bags40k7 days · 15 bags48k7 days · 18 bags
Scottsdale, south of Indian School Rd14 grains per gallon24k14 days · 3 bags24k11 days · 6 bags24k7 days · 9 bags32k7 days · 12 bags40k7 days · 15 bags48k7 days · 18 bags
Scottsdale, Indian School to Chaparral Rd15 grains per gallon24k14 days · 3 bags24k10 days · 7 bags24k7 days · 10 bags32k7 days · 13 bags40k7 days · 16 bags48k7 days · 19 bags
Scottsdale, north of Chaparral Rd15 grains per gallon24k14 days · 3 bags24k10 days · 7 bags24k7 days · 10 bags32k7 days · 13 bags40k7 days · 16 bags48k7 days · 19 bags
Mesa, City Zone12 grains per gallon24k14 days · 3 bags24k13 days · 5 bags24k8 days · 8 bags32k8 days · 10 bags32k7 days · 13 bags40k7 days · 15 bags
Mesa, Eastern and Southern Zones16 grains per gallon24k14 days · 4 bags24k10 days · 7 bags32k8 days · 10 bags40k8 days · 14 bags48k8 days · 17 bags64k8 days · 20 bags
Chandler16.5 grains per gallon24k14 days · 4 bags24k9 days · 7 bags32k8 days · 11 bags40k8 days · 14 bags48k7 days · 17 bags64k8 days · 21 bags
Peoria12.4 grains per gallon24k14 days · 3 bags24k12 days · 6 bags24k8 days · 8 bags32k8 days · 11 bags40k8 days · 13 bags40k7 days · 16 bags
Gilbert10.8 grains per gallon24k14 days · 3 bags24k14 days · 5 bags24k9 days · 7 bags24k7 days · 9 bags32k7 days · 12 bags40k8 days · 14 bags
Glendale13.8 grains per gallon24k14 days · 3 bags24k11 days · 6 bags24k7 days · 9 bags32k7 days · 12 bags40k7 days · 15 bags48k7 days · 18 bags
Tempe12.3 grains per gallon24k14 days · 3 bags24k13 days · 5 bags24k8 days · 8 bags32k8 days · 11 bags40k8 days · 13 bags40k7 days · 16 bags
Surprise, Mountain Vista3.9 grains per gallon24k14 days · 1 bags24k14 days · 2 bags24k14 days · 3 bags24k14 days · 4 bags24k14 days · 4 bags24k13 days · 5 bags
Surprise, Desert Oasis6.2 grains per gallon24k14 days · 2 bags24k14 days · 3 bags24k14 days · 4 bags24k12 days · 6 bags24k10 days · 7 bags24k8 days · 8 bags
Surprise, Surprise Foothills5.3 grains per gallon24k14 days · 1 bags24k14 days · 3 bags24k14 days · 4 bags24k14 days · 5 bags24k12 days · 6 bags24k10 days · 7 bags
Surprise, Circle City8.2 grains per gallon24k14 days · 2 bags24k14 days · 4 bags24k13 days · 5 bags24k9 days · 7 bags24k7 days · 9 bags32k8 days · 11 bags
Queen Creek11.5 grains per gallon24k14 days · 3 bags24k13 days · 5 bags24k9 days · 8 bags32k9 days · 10 bags32k7 days · 12 bags40k7 days · 15 bags
Fountain Hills16 grains per gallon24k14 days · 4 bags24k10 days · 7 bags32k8 days · 10 bags40k8 days · 14 bags48k8 days · 17 bags64k8 days · 20 bags

"32k" means a 32,000-grain softener. Days: time between recharges. Bags: 40 lb bags of salt a year.

2. How many people live in your home?

the number your kit shows, in grains per gallon
Your water is
Very hardAbout 160 lb of minerals flow into your home each year
Softener size to buy
24,000-grain
the size number on the box
Salt it will use
About 9
40 lb bags a year
Set the hardness dial to
14
recharges about every 7 days

What the dial setting means

Every softener has a control valve on top with a setting for your water's hardness, usually labelled "hardness" or "grains". Enter this number there. It tells the softener how hard your water is, so it knows when it is full.

"Recharging" (some manuals say "regenerating") is the softener cleaning itself: it rinses its resin beads with salty water to flush out the minerals they have caught. With this setting it happens on its own, about every 7 days in your home, usually at night.

Set the number too low and hard water slips through before the next recharge. Set it too high and the softener recharges early, wasting salt and water.

Phoenix blends river, canal and well water, so hardness shifts across the city. We use the middle of the range. Source: City of Phoenix Water Services Department, annual water quality report, 2025.

We don't make, sell or install water softeners or filters, and no company pays to be listed or ranked.

How this figure was measured

Who published it

Water authority
City of Phoenix Water Services Department
About the authority
The City of Phoenix department that runs Phoenix's public drinking-water system. A public agency; no company supplied or paid for this figure.
Type of source
Annual water quality report. Every community water system in the U.S. must publish one each year under the federal Safe Drinking Water Act, so it is the utility’s own official record of what is in its water.
Data year
2025
Last checked
15 October 2026, against the original document

What the figure is

What was measured
Total hardness, reported in parts per million and grains per gallon: 10 to 17.6 grains per gallon (171 to 301 mg/L)
Area covered
The whole Phoenix water system
How it was sampled
One range for the whole city water system, as printed in the report.
Where the water comes from
In 2025 about 97 to 99 percent came from surface water: the Salt and Verde rivers (through Salt River Project canals) and the Colorado River (through the Central Arizona Project aqueduct). The rest came from about 20 city groundwater wells.

How we use it

Figure we use
Middle of the published range (13.8 grains per gallon).
Unit conversion
1 grain per gallon = 17.1 milligrams per litre (mg/L), the same as parts per million (ppm)
How we calculate
Daily hardness to remove = people × 75 gallons × grains per gallon. We pick the smallest standard size that lasts about 7 days between recharges, at 3,300 grains removed per pound of salt.
Limits
Hardness varies by street and by season as utilities switch between water sources. A home test result is more exact and overrides this figure.

How the sizing works

Every gallon of Valley water brings a set amount of hardness into your home, measured in grains. A softener holds a certain number of grains before it needs to recharge. So:

  1. Daily hardness = people × 75 gallons a day × your water’s hardness in grains per gallon.
  2. Size needed = daily hardness × 7, so the softener recharges about once a week.
  3. Pick the next standard size up: 24,000, 32,000, 40,000, 48,000, 64,000 or 80,000 grains.

For a family of four in Phoenix (about 13.8 grains per gallon): 4 × 75 × 13.8 is about 4,140 grains a day, or about 29,000 a week, so a 32,000-grain softener.

Why “about once a week”?

Recharging too often wastes salt and water and wears out parts sooner. Going too long between recharges lets the resin sit loaded with minerals. A weekly cycle is the usual middle ground, and it is what the chart above aims for.

When to size up

  • Bigger water use. Pools filled from the house, big gardens on household water, or frequent guests all add gallons.
  • Iron. Some private wells carry iron, which uses up softener capacity faster. Most Valley city water does not, but well owners should test for it.
  • A harder test result. If your own test is higher than the city figure, use your number.

When smaller is fine

One or two people in a lightly used home can go a week or more on a 24,000-grain softener even in very hard water. There is little point paying for capacity that will sit unused.

Common questions

How big a water softener do I need for a family of four?
In Phoenix itself, a 32,000-grain softener. Where the water is about 16 grains per gallon or harder, as in Mesa's Eastern and Southern Zones or Chandler, a family of four needs 40,000 grains.
How big a home is a 48,000-grain softener for?
Size goes by people and water use, not square feet. In Valley water a 48,000-grain softener suits about five or six people, recharging about once a week.
Does it matter what size water softener I use?
Yes. Too small and it recharges every few days, using more salt and water and wearing the valve. Too big costs more up front, and if it goes weeks between recharges the resin sits unused.