Answers · The supply line and the filter
Can I Run a Sub-Zero Without a Water Filter?
The short answer
Yes on a twist-in model, where pulling the cartridge puts the unit into bypass mode, but Sub-Zero calls for that behind reverse osmosis, and on ordinary tap water the cartridge is worth keeping.
Check in this order
- Identify the cartridge: twist-in types come out with a quarter turn, push-in types on some Classic BI models click.
- Bypass a twist-in model by turning the cartridge counterclockwise and pulling it out; the empty socket is the bypass.
- Switch the filter monitor off on a Classic CL model once the cartridge is out.
- Leave a push-in cartridge alone: its bypass plug is no longer available, so the manifold needs upgrading instead.
Past this line it is a technician's job Sub-Zero Repair Tacoma, (206) 472-1140
Behind the answer
On well water, or any supply carrying sediment, keep the cartridge. The Designer installation guide goes further and requires an in-line filter on drawer ice makers where sediment runs high.
Related questions
Do I have to bypass the filter if I add reverse osmosis?
Sub-Zero says yes. Its Designer and PRO installation guides call for the filter to be bypassed behind reverse osmosis, and warn against a copper line after the system. On push-in Classic models that means a manifold upgrade, which is a technician's job: ask Sub-Zero Repair Tacoma, (206) 472-1140.
My model has no filter at all. Can one be fitted inside?
No. Sub-Zero lists the 500 and 700 series and most 600 series models among those built without one, and says an internal filter cannot be added. It does not sell in-line filters either, but a plumber can fit one on the supply line.
- Signed
- Marta Fennimore
- Role
- Refrigeration technician — ice systems and water supply
- In the trade
- 12 years
- Holds
- EPA 608 certified
- Checked
- Sep 18, 2026