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Water Filter for the LG LMX21984ST (LT600P)
✓ 100% compatible — no bypass plug needed
🔧 5-min push-in swap
🇺🇸 Ships from Indiana
Every cartridge that fits this model — pulled live from the catalogue:
✓
LMX21984ST specifics — where the filter actually lives
On the LMX21984ST, the cartridge inside the fresh-food cavity, position varying with dispenser spec, a deliberate placement that keeps the swap away from the door seals and drawer rails. The seat combines push-fit and twist-lock: the cartridge locks with a short rotation after seating; if it rotates freely, it is not seated.
The recurring owner notes: expect the first swap to take longer than the box suggests — aged o-rings grip — so budget ten minutes, not five. The badge reads LMX21984ST, but the chassis reads LM: when LG stamps LM on the plate it is sorting the machine into the 4-door Max class — same water path, same cartridge, different cabinet. Finish codes such as ST change the look, not the plumbing — order the cartridge by model, ignore the finish letter.
LM vs LF — what the prefix tells you
Two prefixes, two missions: The door count differs — 4-door Max against French-door — but the bay and the cartridge order do not. cabinet class 21 cubic feet — a box that size leans on the dispenser, so the six-month cartridge interval earns its keep.
Swap it in 5 minutes
- Press the release (if fitted), twist the old cartridge free, and pull it from the header.
- Wet the new cartridge’s o-ring with cold tap water so it seats without dragging.
- Push the cartridge square onto the header, then give it the locking quarter turn.
- Run two gallons through the dispenser to flush carbon fines, then hold the filter-reset control until the status light clears.
What this filter takes out of your water
| What it targets | Standard that covers it |
|---|---|
| Chlorine taste & odor | NSF/ANSI 42 — aesthetic effects |
| Particulates, Class I | NSF/ANSI 42 — fine sediment |
| Lead | NSF/ANSI 53 — health effects |
| Cysts (cryptosporidium, giardia) | NSF/ANSI 53 — microbial |
| PFOA & PFOS | NSF/ANSI 53 (P473) — varies by cartridge |
Coverage above lists what the standard addresses, not a performance claim for any specific cartridge — removal claims vary by certificate, so check the NSF listing for the exact part number you are buying.
LMX21984ST filter questions
How do I reset the filter light on the LG LMX21984ST?
Lock in the new cartridge first, then hold the reset control for a few seconds — the LMX21984ST manual documents the button for each panel variant.
Does the LG LMX21984ST need a bypass plug when the filter is out?
No — run it empty if you like; the LT600P bay needs no bypass plug, it simply passes water through untreated.
Are off-brand filters safe for a LG refrigerator?
Certified aftermarket cartridges are built to the same NSF test standards as the OEM part, and federal warranty law (Magnuson-Moss) protects your coverage when you use them.
Why is the OEM LT600P cartridge so much more expensive?
Part of the OEM price is the badge and the distribution chain. Certified alternatives meet the same test standards at a lower unit price, especially in multi-packs.
How often should I replace the filter in my LMX21984ST?
Every six months or at the rated gallon capacity, whichever comes first — the LT600P class cartridges all share that service interval.
Do I need to turn off the water supply to change it?
No — the bay is designed for a live swap. Expect a small dribble, keep a towel in reach, and flush a couple of gallons through the new cartridge before the first glass.
Every filter that fits your fridge
This bay takes the OEM LT600P. ClearFit verified-fit alternatives for this exact slot are being staged — every compatible option for your fridge is one lookup away.
Check every filter that fits →This filter expires six months from today
Your HVAC filter is probably on a different cycle. Track them all in one place.
months until this filter should be replaced (200-gal rated life)
Free tool · tracks fridge + HVAC + whole-house · auto-refill optional
More models using this filter
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