The lightest ticket on my May ledger belonged to a Loyola Corners kitchen: $329, parts and labor, to get a Sub-Zero 550 making ice again. The fault was a dual water inlet valve scaled nearly shut by hard water, not the tired ice maker the owner was already pricing out.
I have worked on refrigeration and ice around Los Altos for 14 years, and this failure is a regular. Cubes go hollow first because the mold never quite fills; a few weeks later the ice stops while the dispenser still manages a trickle. That pattern told most of the story.
The Call: Hollow Ice
The call was textbook. A 550 that has sat in the same Loyola Corners kitchen since the early 2000s started throwing hollow, shell-like cubes; a couple of weeks later the bin stopped refilling entirely. The dispenser still trickled, and that detail matters. On a Sub-Zero 550, hollow cubes almost always mean a starved fill, not a dead ice maker.
Three Checks, In Order
First, house water pressure at the shutoff: 58 psi, squarely normal; the supply was ruled out in five minutes. Second, the inlet valve screen, which came out crusted white with mineral scale. Third, the flow test on the valve solenoids: the ice-maker side pushed a weak, restricted stream too feeble to fill the mold before the fill window closed.
One Valve, Same Day
Root cause in one line: hard-water scale had choked the dual water inlet valve until it starved the ice maker. The fix is the part, nothing more. The valve rides on my truck because local water makes it a steady failure, so no ordering and no second appointment. The swap ran under an hour, and the mold filled properly on the first test cycle.
The $329 Bill
The invoice came to $329, parts and labor, and the $89 service call was waived with the repair. As a rough industry estimate, a scaled inlet valve on a Sub-Zero 550 runs $275 to $450 installed, so this job landed low-middle. It stays small because it is one low-labor part. Around here the valve is a wear item, not a defect; the hard water is the real culprit.
When Cubes Go Hollow
If your 550 is throwing hollow ice, act during the warning window. Hollow cubes usually run two to three weeks ahead of a full stoppage, and the repair costs the same either way. Do not buy a new ice maker first; ask for a flow test on the inlet valve. It takes minutes and settles it with a reading, not a guess.