Running reverse osmosis for fridge water gives you clear, hard ice and better-tasting cold water, and it is a simple tee off the permeate line. The one thing that catches people out is pressure: an RO faucet line is low-flow, and a fridge with a long tube run and an ice maker can starve if you plumb it carelessly.
Where to take the tee
Tee off the permeate line after the storage tank and after the post-carbon filter, on the run heading for the dedicated faucet. Taking it before the tank means the fridge gets whatever the membrane is producing at that moment, which is a trickle, and it will never fill the ice tray. Use a proper push-fit tee sized to the tubing, and keep the joint accessible rather than burying it behind the cabinet back panel. Fit a small shutoff valve on the fridge branch at the tee: when the fridge needs pulling out for service you can isolate it without draining the whole system.
The pressure and run-length problem
An under-sink reverse osmosis system delivers modest pressure from a bladder tank, and every foot of narrow tubing and every tight bend takes a little more of it away. A fridge two cabinets away at the end of a long run behind the toe kicks may fill its dispenser fine and still fail to make ice properly, because the ice maker's fill valve needs a minimum pressure to open and meter correctly. The fixes are a permeate pump, which raises delivery pressure from the tank, or a dedicated small booster on the fridge line. Check the appliance maker's minimum supply pressure before you commit.
Do you still need the fridge's own filter?
Water that has been through a membrane and post-carbon does not need the appliance cartridge for taste, and many households fit the bypass plug the manufacturer supplies and stop buying cartridges. Two cautions. Some models will not dispense at all without either the cartridge or the bypass fitted, so get the correct bypass part. And check the appliance warranty language, because a few makers tie coverage to their own filter being in place. If you keep the cartridge, it will simply last a very long time, since almost nothing is reaching it.
Tubing, freezing and first use
Use the tubing size the system uses and food-grade fittings throughout, and leave a service loop of slack behind the fridge so the appliance can be pulled forward without stretching the line. Route the tube where it cannot be crushed by the fridge rolling back: a kinked line is the most common cause of a dispenser that slowed to nothing. Discard the first few batches of ice after commissioning, because new tubing and a fresh cartridge shed a taste. Then keep the pre-filters on schedule, since the fridge line is only as good as the membrane feeding it; our reverse osmosis maintenance guide has the intervals.
Questions people ask about reverse osmosis for fridge
Where do I tee the fridge line into the RO system?
After the storage tank and the post-carbon stage, on the line running to the dedicated faucet. Teeing before the tank starves the fridge because the membrane produces only a trickle at any moment.
Will reverse osmosis make clear ice?
Much clearer than tap water, because cloudiness in ice comes largely from dissolved minerals and trapped air coming out of solution as the cube freezes.
Do I need a booster or permeate pump?
If the fridge is a long run from the system, or its ice maker fill valve specifies a minimum pressure your tank cannot meet, then yes. Short runs on a healthy tank usually manage without.
Can I remove the fridge's built-in filter?
Usually, by fitting the manufacturer's bypass plug, since the water is already treated. Check that your model dispenses with the bypass in place and read the warranty terms first.
Why did my ice maker stop after I connected RO?
Almost always pressure or a kinked line. Check the tubing behind the appliance for crushing, confirm the tee is downstream of the tank, and compare tank pressure against the fill valve requirement.