Which Sub-Zero Water Filter and Air Purification Cartridge Fits My Unit?

Ordering the wrong Sub-Zero filter is one of the easier mistakes to make. There are two physically different styles, several superseded part numbers still listed for sale by third-party sellers, and a separate number entirely for the undercounter ice makers. The cartridge that “looks the same” from a marketplace listing very often is not.

Here are the official numbers, what fits what, and which ones are dead.

Sub-Zero water filter part numbers

Part number	Style	Fits	Status
4204490	Twist-in	Classic (BI, CL), Designer (IT, IC, DEC, DET), 648PRO, PRO3650, PRO4850	Current
9030868	Twist-in	Same family coverage as 4204490	Current
7045454	Push-in	Classic (BI) — color, taste and odor	Current, formerly sold as 7023812
7023812	Push-in	Classic (BI) — color, taste and odor	Superseded by 7045454
7023811	Push-in	Classic (BI)	Discontinued, replaced by 7023812
7009931	Push-in	Classic (BI) — color, taste and odor	Listed for Classic/BI
7005017	Push-in	Classic (BI)	Discontinued, replaced by 7045454
7042803	Cartridge	UC-15I undercounter ice maker, NSF certified	Current
7012333	Cartridge	UC-15I undercounter ice maker	Discontinued, replaced by 7042803

Two things to take from that table.

Twist-in and push-in are not interchangeable. The twist-in family (4204490, 9030868) covers the current Classic and Designer platforms plus all three PRO models. The push-in family covers legacy Built-In units. If the filter you received will not seat, you almost certainly have the wrong style rather than a defective part.

The undercounter ice maker is its own world. A UC-15I takes 7042803. It does not take a full-size refrigerator filter, and the 7012333 you may have written on a note in the cabinet ten years ago is gone.

Verify against the model and serial number on the data plate before ordering. Sub-Zero Customer Care at 800-222-7820 will date the unit from its serial number if you cannot read the tag. On Designer Tall (IT, DET), Designer Drawer (ID) and 700 Series units, the tag is inside the cabinet to the left of the upper drawer.

The air purification cartridge: 7042798

One number, and it is worth understanding what it does.

Sub-Zero’s air purification system is based on NASA-developed technology. It scrubs ethylene gas and odors out of the refrigerator air roughly every 20 minutes. Ethylene is what ripening produce gives off and what makes everything else in the drawer ripen faster, so a spent cartridge shows up as produce that does not last and as a refrigerator that smells like whatever is strongest inside it.

The consumable is part number 7042798. Like the water filters, it is explicitly excluded from the warranty — Sub-Zero’s residential limited warranty states that replacement water filters and air purification cartridges are not covered by the product warranty.

What a filter does, and what it does not

A refrigerator water filter is an activated carbon cartridge with a particulate stage. Its job is to handle chlorine taste and odour and to keep sediment out of the water you drink and out of the small components downstream of it. That is the whole job.

It is not a softener. No cartridge that fits inside a refrigerator door frame is going to change the dissolved mineral content of your supply, and buying a more expensive one does not change that. Treating the supply itself is done where the water enters the house, or at a point-of-use stage feeding one specific appliance.

What a filter genuinely controls is flow, and flow is where an appliance notices it.

A cartridge approaching the end of its life restricts. The dispenser slows, the stream goes thin, and a glass takes noticeably longer to fill. Upstream of that, the ice maker’s fill valve — which opens for a fixed interval and meters whatever volume gets through it — starts underfilling the mold. That is precisely why Sub-Zero names low water pressure for small or hollow cubes, and why reseating or replacing the filter sits near the top of its own ice maker diagnostic sequence rather than near the bottom.

Two traps worth knowing.

The invisible cartridge. A great many houses have a whole-home or inline filter that nobody has thought about in years. It is invisible at the taps, where pressure is generous, and it is decisive at a solenoid valve that only opens for a few seconds at a time. If the refrigerator filter is new and nothing has changed, that is the next thing to go and find.

The marketplace cartridge. Third-party filters vary considerably in fit tolerance and in flow rate. A cartridge that seats slightly proud is not an obvious failure; it is a slow leak inside the cabinet that shows up weeks later as water where it should not be. If you use one, check what it is genuinely certified for rather than what the listing claims, and check that it seats with the same positive action the original did.

Change on the manufacturer’s interval, and change sooner if dispenser flow drops or cubes come out undersized. Those two symptoms are the cartridge telling you it is spent, and they both arrive long before the water tastes any different.

Changing the filter without making a mess

Have a towel ready. There will be some water in the housing.

Twist-in filters seat and release with a quarter turn. Push-in filters press home until they click. Either way, seat the new one firmly. A partially seated filter is a slow leak, and it is also one of the checks in Sub-Zero’s own ice maker diagnostic sequence — reseating the filter is on the list before anything gets replaced.

After fitting, run several quarts through the dispenser to purge air and carbon fines from the line. The water will look cloudy at first. That is air, not a problem.

If the ice maker was already struggling before the filter change, do not expect it to catch up immediately. Sub-Zero’s sequence is to allow 24 hours, confirm the ice maker is switched on, confirm the freezer is at or below 5°F with 0°F recommended, clean the condenser if it has not been done in 6 to 12 months, verify the bin is properly installed and level, check any whole-home or inline filter for expiry, confirm the supply valve is open, and check that the shut-off arm is down and the white plastic rudder arm is attached.

A simple maintenance rhythm

Pair the filter change with the condenser cleaning. Sub-Zero’s condenser interval is every 6 to 12 months, more often with pets, and doing both at once means one date to remember instead of two. Swap the air cartridge, 7042798, on the same visit and the whole thing takes half an hour.

If the ice maker still will not produce after all of that, or you find water sitting in the ice maker area, that is past the consumable stage. We are an independent Sub-Zero repair shop in Fruit Cove with EPA Section 608 certified technicians, and the diagnostic is $129 flat, credited toward the repair when you approve the work.