What your water does to the ice.
Phoenix reported 10 to 17.6 grains per gallon in 2025; Mesa runs as high as 22 and Chandler averages 16.5. A built-in ice machine makes clear ice by freezing water in thin layers and washing away what it rejects, and in water like this, what it rejects is a great deal of mineral. That is not a fault. It becomes one when the cleaning that the makers actually specify never happens.
What the Cities Publish
Hardness is not a health standard and none of these utilities treat for it, so each one simply publishes the number. Grains per gallon is the unit an appliance manual uses; to convert from milligrams per litre, divide by 17.1.
| Where | Grains per gallon | As the utility puts it | Source |
|---|---|---|---|
| Phoenix | 10 – 17.6 | 172–302 ppm across the distribution system | City of Phoenix, 2025 Water Quality Report |
| Scottsdale: south of Indian School Road | 13 – 15 | 230–260 ppm | City of Scottsdale, 2024 Water Quality Report |
| Scottsdale: Indian School to Chaparral | 13 – 17 | 215–285 ppm | City of Scottsdale, 2024 Water Quality Report |
| Scottsdale: north of Chaparral Road | 13 – 17 | 230–290 ppm | City of Scottsdale, 2024 Water Quality Report |
| Mesa | 12 – 22 | “depending on the water source that serves your area” | City of Mesa, water quality |
| Chandler | 5 – 20, average 16.5 | the average is the figure the city leads with | City of Chandler, Water Quality FAQs |
| Gilbert | 8 – 10 | the softest of the five | Town of Gilbert, Public Works |
Paradise Valley, Fountain Hills, Cave Creek and Carefree are served by providers other than the city water departments above, and we have no published figure for them. The number for your address is in the annual water quality report your own provider sends.
Why an ice machine minds, and a freezer doesn’t.
A freezer never meets your water. An ice machine meets all of it. Cubes from a freezer tray are cloudy because the water freezes all at once and traps air and dissolved minerals in the middle; a built-in machine freezes in thin layers against a chilled plate and washes what it rejects away as it goes. That rejection is the whole reason the ice is clear, and the harder the water, the more there is to reject on every single cycle.
So the same machine, installed identically, reaches the point where it needs attention sooner in Chandler at an average of 16.5 grains than in Gilbert at 8 to 10. Nothing is broken in either one. One of them simply arrives at the maintenance interval first.
What it looks like from the kitchen is a slow slide rather than a failure: cubes get smaller, then cloudier, then hollow; production falls off; the ice starts to taste of the bin. A thickness sensor reading through a film of mineral stops the harvest at the wrong moment, and a fill valve furred on the inside passes less water than the cycle expects. Every one of those reads as “the ice maker is broken”, and none of them is.
What Sub-Zero Actually Instructs
- 01
Clean and sanitize every six months
Every surface that meets the water system, on an undercounter ice maker, and Sub-Zero says that interval stands regardless of the water filtration system fitted.
- 02
Use the cleaner made for the machine
The solution is what removes limescale, calcium buildup from hard water and other mineral deposits. Sub-Zero does not recommend any other cleaner or sanitizer, including bleach; vinegar only as a last resort, and only on the interior.
- 03
If it will not hold six months, test the water
Sub-Zero’s own answer to a machine that needs cleaning more often is to have the water quality tested and treated, not to clean it more often forever.
- 04
The filter is 750 gallons, or a year
Whichever comes first. A fresh filter does not remove scale that has already formed, which is why it does not replace the six-month clean. The refrigerator cartridge runs on its own two triggers. On a model without a dispenser, discard the first two full containers of ice after a change.
Maintenance, not a repair.
Descaling is housekeeping. It is on the list above because it is the single most useful thing an owner in this valley can do for an ice machine, and because we would rather tell you to run the cleaner than take $119 to find limescale.
It becomes our work when cleaning does not bring it back: a fill valve passing too little water, a thickness sensor that has drifted out of adjustment, a pump or a drain that no longer clears between cycles, or a sealed-system fault behind it all. What each of those parts is and how it fails is on the parts page.
One test separates most of it before anyone drives out: if the water dispenser still runs normally, the supply into the house is fine and the fault is inside the machine.
Hard Water Questions
How hard is the water where I live?
The city publishes it. Phoenix reported 10 to 17.6 grains per gallon across its distribution system in 2025, Scottsdale 13 to 17 depending on which side of Indian School and Chaparral Roads you are on, Mesa 12 to 22 depending on the source serving your area, Chandler an average of 16.5 against a range of 5 to 20, and Gilbert 8 to 10, the softest of the five.
My ice went small and cloudy. Is the machine broken?
Not necessarily, and this is the one fault worth trying yourself before calling anyone. Sub-Zero says to clean and sanitize an undercounter ice maker every six months whatever filtration is fitted, using the cleaner made for it, and that the solution is what removes limescale and calcium buildup from hard water. If the ice is still small or cloudy after a proper clean and a fresh filter, the fault is inside the machine rather than in the water.
Does a water softener solve it?
It changes what arrives at the machine, and it has a trade-off the City of Mesa states plainly: sodium in softened water rises by about 8 milligrams per litre for every grain of hardness removed. It does not change the maintenance either way: Sub-Zero’s instruction is to clean and sanitize every six months regardless of the water filtration system used.
How often does the water filter need changing?
Sub-Zero rates its filter for 750 gallons, or one year, whichever comes first. The filter and the cleaning are separate jobs: a fresh filter does not remove scale that has already formed, which is why the six-month clean stands whatever filter is fitted. After a filter change on a model without a dispenser, Sub-Zero says to discard the first two full containers of ice.
When is it a repair rather than cleaning?
When cleaning does not bring it back. A fill valve passing too little water, a thickness sensor that has drifted, a pump or drain that no longer clears between cycles, or a sealed-system fault are all repairs. We would rather tell you to run the cleaner than sell you a visit that finds limescale.
Sources
- City of Phoenix, 2025 Water Quality Report: total hardness 172–302 ppm, 10–17.6 grains per gallon, from the distribution system table.
- City of Scottsdale, 2024 Water Quality Report: approximate hardness levels by boundary: south of Indian School Road, Indian School to Chaparral, north of Chaparral.
- City of Mesa, common water quality concerns: 12 to 22 grains per gallon depending on the source serving the area, and the sodium added by softening.
- City of Chandler, water quality FAQs: 5 to 20 grains per gallon, average 16.5.
- Town of Gilbert, Public Works water FAQ: average hardness 8 to 10 grains per gallon.
- Sub-Zero, undercounter ice maker cleaning: the six-month interval, the cleaner, bleach and vinegar, and testing the water when the interval will not hold.
- Sub-Zero, undercounter ice maker water filter: 750 gallons or one year, and the first two containers of ice after a change.
Written from these sources and reviewed on by Aphelion Appliance Repair, Phoenix. Utilities republish these figures every year and they move; the report for the current year is on each provider’s own site. Cleaning intervals and cleaners differ by model, the use and care guide for yours is the one that counts.
Read Next
- No ice, or not enough?Sub-Zero’s own production rates and the seven checks before anyone is called.
- What a Phoenix summer asks of a built-in refrigeratorRoom heat, condenser dust and monsoon outages, and five checks before you call.
- Chandler: hard water and the ice makerThe same numbers, for the city that leads the valley on hardness.
Cleaned it, and still no ice?
Tell us the make and what the cubes look like. We call you back to set a time.