The Sub-Zero UC-15I(P) undercounter ice maker takes water filter 7042803, the current number for the older 7012333, and Sub-Zero says to replace it every six months, after a prolonged shutdown, or when the red REPLACE FILTER light comes on. After fitting the new cartridge, touch and hold CLEAN for 6 seconds to reset the reminder, then discard the first batch of ice.
The UC-15I(P) filter shapes more than flavor. A fresh 7042803 means cleaner-tasting ice and less sediment at the water valve, while a clogged or mismatched cartridge shows up as small cubes, slow production, off flavors or a drip at the cabinet front.
Which cartridge does a UC-15I(P) take?
The Sub-Zero UC-15I(P) uses water filter 7042803. Older paperwork and some parts listings still show 7012333, the same filter under its former number, so either number on the box is the right part.
Not every Sub-Zero ice maker has a filter. The DEU1550I undercounter ice maker does not ship with one, and UC-24 undercounter, DEU undercounter refrigeration and ID drawer models have no internal water filter, so confirm the model on the serial tag before ordering.
Sub-Zero refrigerator filters are a separate family. The twist-in 4204490, interchangeable with 9030868, fits Classic (BI, CL) and Designer (DEC, DET) refrigerators plus 648PRO, PRO3650 and PRO4850 models, not the ice maker.
How often does the filter need changing?
Sub-Zero gives the UC-15I(P) filter three triggers, whichever comes first: six months, a prolonged shutdown, or the REPLACE FILTER indicator glowing red. The indicator comes on after 8000 ice-making cycles, so it is a counter, not a sensor; a busy bar may hit 8000 cycles early, while a lightly used Sub-Zero ice maker can run far past six months without it.
Hillsborough is codified as a residential estate town, with half-acre minimum lots and no commercial businesses, so a replacement 7042803 is not a quick errand. Larger properties, including those around Carolands Chateau, may run a UC-15I(P) in a pool house or guest bar that sits idle for weeks; a fresh filter before reopening covers the prolonged-shutdown rule, and a spare on the shelf makes that easy.
The Sub-Zero refrigerator filter in Classic (CL) and Designer (DET, DEC) models lasts up to 750 gallons (2,839 L) or twelve months, so one reminder does not cover both appliances.
Swapping the cartridge, step by step
Replacing the Sub-Zero UC-15I(P) filter needs no special tools. The use and care guide shows where the cartridge sits; check it before removing any panel.
1. Confirm the new cartridge reads 7042803 or 7012333, and set a towel and shallow pan below the filter.
2. Close the water supply valve feeding the UC-15I(P).
3. Remove the old cartridge as the guide shows, keeping it level so trapped water drains into the pan.
4. Seat the new 7042803 until it locks, reopen the valve, and watch the filter head for drips.
5. Touch and hold CLEAN for 6 seconds to clear REPLACE FILTER.
6. Discard the first batch of ice the UC-15I makes, as Sub-Zero directs, so carbon fines and air from the new cartridge stay out of drinks.
If a new Sub-Zero filter resists seating, stop rather than force it; a cracked filter head turns a five-minute swap into a water-line repair.
How do you reset the indicator after a swap?
On the Sub-Zero UC-15I(P), the REPLACE FILTER light clears when CLEAN is touched and held for the full 6 seconds after a new filter goes in. Touching CLEAN is also how the cleaning cycle begins, and Sub-Zero notes a UC-15I clean cycle cannot be canceled once started, so a short tap risks committing the machine to a full run.
A UC-15I(P) filter light that stays red after a full hold points to a control issue rather than the cartridge, and deserves a technician's look.
What does water quality do to ice and the machine?
Tap water carries chlorine, sediment and dissolved minerals, and the Sub-Zero UC-15I(P) freezes whatever reaches it into every cube. Ice maker filters of this kind mainly address taste, odor and sediment, so an overdue cartridge often shows first as flat or chemical-tasting ice.
Hardness is a separate problem for a Sub-Zero ice maker: calcium and magnesium pass through most taste-and-odor filters and leave scale on the evaporator and water path, slowing production and clouding cubes. Sub-Zero's answer is a clean and sanitize routine every six months: touch CLEAN, empty the bin, add 4 ounces (115 ml) of cleaner when the light flashes, then repeat with 1 tablespoon (15 ml) of sanitizer. Each cycle takes about 30 minutes.
The UC-15I(P) shares its cleaner and sanitizer with the DEU1550I; neither is interchangeable with 315I cleaners, and Sub-Zero's renamed descaler is the same cleaner.
The UC-15I condenser behind the kickplate also needs cleaning every six months. Brush or vacuum without bending the aluminum fins and skip chemical cleaners, which Sub-Zero calls unnecessary; a dusty condenser cuts ice output and is easily blamed on the filter.
Can a clogged or wrong filter stop ice production?
A neglected or mismatched cartridge can slow a Sub-Zero UC-15I(P) badly and, at worst, stop it: a clogged filter restricts the water drawn each cycle, and a poorly seated one can block flow or leak. The REPLACE FILTER light warns of neither.
Small, thin or hollow cubes: a restricted Sub-Zero filter is starving the fill. Replace a cartridge older than six months and discard the first batch; if cubes stay small on a fresh 7042803, a technician should check water pressure, the inlet valve and the supply line.
Falling output: a UC-15I slowed by a clogged filter, scale or a dusty condenser. Replace an overdue cartridge, run the clean and sanitize routine if due, and clean the condenser; output that stays low after all three points to a component fault.
Off-tasting ice: a Sub-Zero ice maker with an overdue cartridge, or a filter left in through a long shutdown. Fit a fresh filter, discard the old ice and sanitize; taste that returns within weeks calls for a look at the supply line.
Water at the cabinet front after a change: a UC-15I(P) cartridge not fully seated, a damaged O-ring or the wrong part. Close the valve, reseat and recheck the part number; a drip that continues with the correct filter seated is a water-line repair.
Filter changes on a Sub-Zero ice maker are owner work; leaks, low pressure, valve faults and control problems are not. A diagnostic visit starts at $195, and ice maker or water-line work typically plans at $310-$985 once the cause is confirmed.