Water Filter for the LG LMX21981ST (LT600P)

Your LG refrigerator takes the LT600P slot. Below is every filter that fits — OEM and certified alternatives — with real prices.

✓ 100% compatible — no bypass plug needed

🔧 5-min push-in swap

🇺🇸 Ships from Indiana

LMX21981ST · Quick Facts

TYPE

refrigerator

YEARS MADE

—

FILTER LOCATION

in the fresh-food compartment, placement dependent on the dispenser package

FILTER SLOT

LT600P bay

REPLACE EVERY

Every 6 months

ALSO BRANDED AS

—

LMX21981ST · Quick Facts

Filter locationin the fresh-food compartment, placement dependent on the dispenser package

Filter slotLT600P bay

Replace everyEvery 6 months

Typical installTwist or push — 5 minutes, no tools

Every cartridge that fits this model — pulled live from the catalogue:

✓

Verified fit for LMX21981ST. Cross-checked against LG service documentation — this model family uses the LT600P bay with no chip or bypass restrictions.

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LMX21981ST specifics — where the filter actually lives

The filter bay on the LMX21981ST in the fresh-food compartment, placement dependent on the dispenser package, the same estate every 4-door Max refrigerator in this family uses. This is a push-twist style bay: a push to register, a turn to lock; the sequence is printed on most cartridges for a reason.

Two quirks worth knowing before you order: a stiff first removal on builds that sat on the same cartridge for years, and an indicator light that wants a manual reset after a non-OEM cartridge is seated. LM is not a trim code, it is a chassis statement: LM machines come from the 4-door Max program, and LG’s parts system rewards you for knowing it: one cartridge family covers the run. Finish letter sets like ST never alter the bay; the LT600P line fits the whole set.

LM vs LF — what the prefix tells you

LM versus LF is the first fork in the parts catalog: Ordering by prefix works because LM means 4-door Max and LF means French-door in this catalog — and the cartridge pool overlaps both. The two digits after the letters are the cabinet size: this is a 21 cu ft refrigerator, which sets how much dispenser work the cartridge does between changes.

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.

LMX21981ST filter questions

How do I reset the filter light on the LG LMX21981ST?

With the new cartridge seated, press and hold the filter reset until the light clears — panel placement differs, so the LMX21981ST manual’s filter section has the exact control for your trim.

LMX21981ST with no water filter installed — safe, or does it need a bypass?

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 LMX21981ST?

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

OEM LT600P cartridge

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 →