Ice Machine Scale and Hard Water in the Bay Area

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Updated October 14, 2026

Quick answer

Scale is the white mineral crust left behind as an ice machine freezes water. It slows freezing, delays harvest, clouds the ice and wears out parts. Bay Area water ranges from soft to very hard: SFPUC water averaged 62 mg/L in 2025 and EBMUD plants sampled 16–64 mg/L, while Zone 7 groundwater averaged 318 mg/L and Santa Clara County groundwater averages over 250 mg/L.

How hard is your water?

Hardness depends on where your water comes from, not just your city. Many Bay Area retailers blend sources, and hardness can change through the year.

Water supplier (area)	Hardness as CaCO3	Published in
SFPUC (San Francisco and regional wholesale customers on the Peninsula and in the South Bay)	8.1–112 mg/L, average 62	SFPUC 2025 Water Quality Report
EBMUD (much of the East Bay)	16–64 mg/L across treatment plants (about 1–4 grains/gallon)	EBMUD plant samples, 6 Oct 2026
Zone 7 (Livermore, Pleasanton, Dublin) surface water	56–152 mg/L, average 88	Zone 7 2025 CCR
Zone 7 groundwater	35–452 mg/L, average 318	Zone 7 2025 CCR
Valley Water treated surface water (Santa Clara County)	Average under 120 mg/L	Valley Water
Santa Clara County groundwater	Average over 250 mg/L	Valley Water

Valley Water classes anything over 180 mg/L as very hard. Your own retailer may blend sources, so check its annual Consumer Confidence Report for your address.

What hardness means for your machine

Hardness (mg/L as CaCO3)	Valley Water class	Practical effect on an ice machine
Under 60	Soft	Scale builds slowly; manufacturer's minimum interval is usually enough
60–120	Moderately hard	Visible scale within months; filtration recommended
120–180	Hard	Shorter descale interval; scale-inhibiting filter
Over 180	Very hard	Descale every three to four months is common; flakers need close watching

Ranges per Valley Water's classification; the effects column is practical guidance, not a manufacturer rule.

What scale does to an ice machine

Slower ice. Scale insulates the evaporator, so each freeze takes longer. See slow production.
Harvest problems. A rough surface grips the ice. See won't harvest.
Cloudy and misshapen cubes. Blocked distribution holes leave dry spots.
Auger wear on flakers. Scale adds drag to the auger and gear motor and causes squealing. See flaker machines.
Sensor faults. Scale on probes and infrared lenses causes early harvests or a machine that stops with an empty bin.

Filtration and treatment

Most manufacturers recommend a water filter matched to the machine's capacity. Filters reduce sediment, chlorine taste and, with scale-inhibiting cartridges, the rate of scale buildup. They do not make hard water soft. Change cartridges on the filter maker's schedule or sooner if pressure drops. See ice machine water filters.

Descaling

Descaling uses the manufacturer's approved cleaner to dissolve mineral crust. Manitowoc, for example, calls for descaling and sanitizing every six months, and more often where water conditions require it. Hoshizaki's cleaning sheets give model-specific minimums. In very hard water, a three- to four-month schedule is common. See which cleaner to use.

Signs scale is building

White crust in the water trough or on the curtain.
Harvests getting longer week by week.
Cloudy ice that was once clear.
On flakers: squealing, popping or a high-amps light.

Manufacturer descale intervals

Brand	Stated minimum
Manitowoc	Descale and sanitize every six months; test water if more is needed
Scotsman	Sanitize at least every six months; scale removal on the six-month maintenance list
Ice-O-Matic	Clean and sanitize at least every six months, no more than monthly
Follett	Clean, descale and sanitize semi-annually (minimum)
Hoshizaki	Model-specific; e.g. at least once a year for KM-61/101/151

Step-by-step: checking for scale

Turn the machine to off or clean mode per the manual.
Look at the water trough, distribution tube and curtain for white or tan crust.
On cube machines, look at the evaporator edges; on flakers, listen for squealing.
Check the filter's date and pressure.
Compare current freeze or harvest times with what they were after the last cleaning.

What a technician does on a descale visit

We test hardness at the machine, descale with the manufacturer's approved cleaner, hand-clean removable parts, sanitize, check the filter and recommend a cartridge and interval for your water. On flakers we check auger load and bearings while the machine is open.

Seasonal changes

Hardness is not fixed. Blended systems shift between sources over the year, and drought years can increase groundwater use in some areas. If scale suddenly builds faster than usual, check your retailer's latest water quality data or have the water tested at the machine.

Softeners and RO water

Do not add a softener or reverse osmosis system without checking your ice machine manufacturer's water requirements first. Ice-O-Matic, for example, notes that RO water may call for more frequent sanitizing. Scale-inhibiting cartridge filters sized for the machine are the usual starting point.

When to call a technician

If scale has built up behind panels or on the evaporator, or a flaker is squealing, book a professional descale before it damages the evaporator or gear motor.

Open 7 days, 8 AM to 5 PM, with emergency service until 9 PM. CA Lic. #776244.

Call 1-800-266-5243 Request service online

Frequently asked questions

Is Bay Area water hard?

It depends on the source. Santa Clara County groundwater is very hard by Valley Water's scale; surface water supplies are softer.

Will a water softener help my ice machine?

Ask your manufacturer first. Some advise against softened water for certain models; scale-inhibiting filters are the usual choice.

How often should I descale?

At the manufacturer's interval, commonly every six months, and more often in hard water.

Can scale damage the machine permanently?

Yes. Heavy scale can ruin evaporator plating and strain the gear motor on flakers.

How hard is East Bay water?

EBMUD's plant samples in October 2026 ranged from 16 to 64 mg/L, which is soft to moderately hard.

How hard is Livermore and Pleasanton water?

Zone 7's 2025 report lists surface water averaging 88 mg/L and groundwater averaging 318 mg/L; your tap water depends on the blend.

Related guides

Sources

Published by Cool Aid Air Conditioning & Refrigeration, a family business serving the Bay Area since 1966. Owner Jim McKinny holds California C-20 and C-38 contractor licenses and EPA Universal certification. Repairs we complete carry our 1-year parts & labor warranty.

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