When the ice tastes wrong, the fault is upstream

The test that splits the problem in two

This takes five minutes and saves people from buying parts they did not need. Draw a glass from the dispenser if the unit has one, or from the nearest tap on the same supply if it does not, and taste it against a glass of bottled water. If that water carries the same off note the ice does, the fault is upstream of the machine and the ice maker is an innocent witness, faithfully freezing what the house handed it. If the water tastes clean while the ice does not, the water was fine when it arrived and the ice picked the flavor up afterward, which puts the fault inside the freezer. That fork decides which half of this guide applies to you, and it explains why swapping a module so often changes nothing. The module fills, freezes and harvests. It has no filtration in it and no opinion about taste.

• Water wrong and ice wrong: the cartridge, the supply line and whatever is upstream of them
• Water clean and ice wrong: the bin, the freezer contents and the mold
• Only the first glass of the day is bad: stagnant water sitting in the line

If the water tastes wrong too: everything upstream of the fill valve

Start with the cartridge, because it fails silently and on a schedule almost nobody keeps. The carbon in a water filter stops removing chlorine and taste compounds well before it restricts flow, so by the time anyone notices the dispenser slowing, the taste has been drifting for months. Next is the line. A long run of plastic tubing gives water a flat, faintly plastic note in its first weeks, and old poly tube that has been in a wall for decades gives a worse one permanently; copper with a saddle valve on it can add a metallic edge as the valve corrodes around the pierce point. Then whatever else the house does to the water first. A softener produces water that tastes salty and flat and is a poor thing to feed an ice maker from. Reverse osmosis tastes of very little, which is fine, but many systems deliver far less pressure than a fill valve expects and can quietly cause short cubes too. Southern California water is mineral heavy to begin with, which is why the interval printed on the cartridge box is optimistic in a house that entertains through the summer.

• Water cartridge past its interval, which is the cause in most cases
• Stagnant water in the line after a vacation or a rarely used dispenser
• New or aging plastic supply tube adding a flat or plastic note
• A corroding saddle valve on old copper
• A softener feeding the ice maker, giving salty, flat ice
• A reverse osmosis feed with pressure too low for the fill valve

If the water is fine: the bin, the air and the mold

Ice is porous and cold, which makes it one of the better odor absorbers in the kitchen. Cubes sitting in a bin for a month sublimate, shrink, weld into clumps and take on the smell of everything around them, so a bin that has not been emptied since spring tastes of the freezer regardless of how clean the water was. Unwrapped or poorly wrapped food is the usual source, and it does not take much: an open bag of fish or a dish of leftovers under plastic wrap will flavor a bin within days. Scale is the other one, building in the mold over years and holding a stale film of water between fills. One point catches people out on a Sub-Zero specifically. The air purification cartridge cleans the compartment it sits in, and because dual refrigeration means no air crosses between the fresh-food side and the freezer, a cartridge serving the fresh-food compartment does nothing at all for a freezer that smells.

• Old ice that has sat in the bin for weeks, absorbing everything around it
• Unwrapped or loosely covered food anywhere in the same compartment
• Mineral scale in the mold holding stale water between fills
• A bin returned to the freezer still damp and now carrying a musty film
• A gasket admitting humid room air, which stales the whole compartment

The things that look like a taste fault and are not

Cloudy ice is the most reported non-fault in the trade. Cubes freeze from the outside in, so dissolved minerals and air are pushed toward the middle and end as a white core, and in mineral-heavy water that core is very visible. It is not dirt, it indicates no fault, and no repair removes it. White flakes or grit in the bottom of a glass are scale coming through from the supply, which points at the cartridge rather than the machine. Cubes welded into a sheet mean the ice has been partly melting and refreezing, which is a temperature or a door problem. Short, hollow or half-formed cubes are a fill problem, with causes running from the cartridge to supply pressure to the inlet valve screen to a fill tube starting to ice. And a strong plastic smell in the first week of a new machine or a new supply line is usually exactly what it appears to be, and it clears after a few full bins have been made and thrown away.

The routine that clears most of it, in order

Change the water cartridge, then purge the line properly, a couple of quarts at least and more if the run is long, until the water is clear rather than merely flowing. Empty the bin completely and do not keep the old ice, however wasteful it feels, because it is the reservoir the flavor is stored in. Wash the bin in warm water with a little plain dish soap, or a mild baking soda solution if there is a musty note to shift, rinse thoroughly, then dry it completely before it goes back, since a damp bin freezes to its shelf and grows the same film again. Throw away the next two or three harvests, which clears carbon fines and any water standing in the mold. Seal strongly flavored food properly rather than covering it. What not to do matters more: no bleach, no ammonia, no scented cleaner and no vinegar soak inside a freezer, because the plastics absorb all of them and the ice tastes of it for months. Nothing metal to scrape a mold either, since there is a heater under it and a coating on it.

• Replace the water cartridge and purge until the water runs clear
• Empty the bin completely and discard the old ice
• Wash in warm water with mild dish soap or baking soda, rinse, dry fully
• Discard the next two or three harvests
• Seal strongly flavored food properly instead of covering it
• Check the age of the air purification cartridge in that compartment

When it is not the water at all

Three patterns take this out of the maintenance column. The first is an off taste arriving with a general staleness across the whole compartment, along with condensation around a door or frost that keeps returning; that is a seal admitting room air continuously, and the ice is simply the most sensitive thing in there to it. The second is a musty odor that returns within days of a thorough clean, worth tracing to the drain and the evaporation pan rather than the bin, because a drain that has grown a biofilm reintroduces the smell on every defrost. The third is the one to act on: a sharp chemical or burning odor that appeared suddenly, particularly alongside a cabinet no longer holding temperature. That is not a water problem and not a cleaning problem. Stop using the ice and have the machine looked at.