Small or hollow ice cubes almost always point to one of three things: the machine isn’t getting enough water, the refrigerant charge is low, or scale has built up on the evaporator plates. Each causes a slightly different symptom, and knowing which one you’re dealing with saves a lot of guessing.
What “small” vs “hollow” actually tells you
These aren’t the same failure. Small cubes mean the freeze cycle is completing but cutting off early, so the ice doesn’t reach full size before it harvests. Hollow cubes (the shell is there but the center didn’t freeze solid) usually mean water flow is uneven or the refrigerant isn’t absorbing heat efficiently.
If you’re getting both, start with water supply. If cubes are consistently small but solid, refrigerant is more likely.
Low water supply or a bad water inlet valve
This is the most common cause and worth checking first because it’s the cheapest fix.
The water inlet valve controls how much water fills the sump or distribution tray each cycle. When it sticks partially closed, or when the screen inside gets clogged with sediment, the machine doesn’t get enough water. The freeze cycle runs on whatever’s there, and you get small or under-filled cubes.
Safe things to check yourself: Is the supply line shutoff fully open? Is the line kinked? What does water pressure read at the machine? Most commercial ice machines need 20-80 PSI, though the exact spec varies by model. Low building pressure at a particular fixture isn’t rare.
If pressure is fine and the valve screen is clear, the solenoid inside the valve is likely failing. Replacing it means shutting off water supply, disconnecting lines, and swapping the valve assembly. That’s a job for a tech. A leaking connection after an incorrect valve swap creates a whole separate problem, and the labor to fix it costs more than just calling someone in the first place.
Scale and mineral buildup on the evaporator
In the Bay Area, water hardness varies by city. Scale accumulates on the evaporator grid over months, acting as insulation between the refrigerant and the water you’re trying to freeze. The machine runs its normal cycle, but heat transfer is poor, so the ice never fully freezes before harvest.
This shows up as cubes smaller than normal, often cloudy or irregular in shape. On a plate-style evaporator, you might see white or gray mineral deposits if you look inside.
Running a manufacturer-approved descaling cycle is routine maintenance most owners can handle. Most commercial machines have a built-in cleaning cycle, and you run a nickel-safe descaler through it. Plan on doing this every 3-6 months in hard-water areas. If it’s been over a year, start there before anything else.
If cube quality doesn’t improve after descaling, the scale buildup may be heavy enough that the evaporator plates need hands-on inspection. At that point you need a tech to open the machine and assess whether the plates are compromised or there’s something else going on.
Low refrigerant
If water supply and scale are both ruled out, the next most likely cause is a low refrigerant charge.
Refrigerant doesn’t deplete on its own. If it’s low, there’s a leak somewhere. The symptoms are usually gradual: cubes get a little smaller, then more hollow, then the machine produces less and less.
A tech can check this quickly with gauges. If suction pressure is low and superheat readings are off, that points to refrigerant. The repair involves finding and sealing the leak, then recharging. This isn’t a DIY job. Handling refrigerants requires an EPA 608 certification, and getting the charge wrong after a leak repair wastes the refrigerant and usually means another service call.
How a technician diagnoses it
A good tech starts with the basics before opening refrigerant circuits. They’ll check water pressure at the machine, inspect the inlet valve and filter, look at the evaporator for scale, and verify harvest cycle timing. A lot of these calls get resolved without touching refrigerant at all.
If refrigerant is suspected, they’ll pull manifold gauges, check for leaks with a detector, and watch ice thickness on the evaporator during a freeze cycle. On most commercial machines, the freeze and harvest cycles are visible and measurable, so the diagnosis is usually clear once you know what you’re looking for.
What you can safely check yourself
- Confirm the supply shutoff is fully open
- Inspect the supply line for kinks or obvious damage
- Check water pressure at the machine
- Replace the water filter if it’s overdue
- Run a manufacturer-approved descaling cycle with a nickel-safe cleaner
If those don’t fix it, the problem is inside the machine and needs a tech.
Call us
If you’ve checked water supply, replaced the filter, and run a descaling cycle and the cubes are still off, the issue is inside the machine. A failing inlet valve, scale-damaged evaporator plates, a refrigerant leak, or a harvest cycle fault all require disassembly and the right diagnostic equipment. Getting it wrong on anything refrigerant-side can void the warranty and turn a straightforward repair into a bigger one.
We work on commercial ice machines regularly across the Tri-Valley and East Bay. Call us or book at adriumservice.com and we’ll get you on the schedule fast, often same or next day when we can.