An inline filter sits in the small tube feeding a refrigerator rather than in a bay inside it, and for a number of appliances it is the better arrangement. It suits fridges with no internal filter position, models whose own cartridges are expensive or authenticated, and households who want a larger cartridge with a longer service life.
When it is the right choice
Older and simpler refrigerators with a water and ice supply but no internal filter bay. Models whose proprietary cartridges cost a great deal or which authenticate them electronically, where an inline filter on the feed lets a standard cartridge do the work. And households wanting a certification the internal cartridge does not carry, or simply a larger element with a much longer interval than a bay sized cartridge can offer.
Fitting it into the feed
The appliance is fed by a small diameter tube from a shut off valve, usually under a nearby sink or at a cold line behind the fridge. Close that valve, relieve the pressure, and cut the tube where the filter will sit, leaving enough slack that the appliance can still be pulled out. Fit the filter with the flow arrow pointing towards the refrigerator, push each connection fully home and pull back gently to confirm seating. Mount the body to the wall or cabinet rather than leaving it hanging on the tubing.
Deciding what happens to the internal filter
Two options and they differ noticeably. Keeping it as a second stage means two cartridges in series, which slows the dispenser and doubles what you buy. Removing it and fitting the manufacturer's bypass plug is usually the better arrangement, and on models that authenticate the cartridge electronically that may not be possible, in which case the inline filter is either redundant or you are paying twice. Check the appliance's behaviour before ordering.
Commissioning and remembering it
Open the valve slowly and check every joint by hand, then again an hour later, since push fittings often weep only after pressure settles. Run several litres through the dispenser and discard the first two batches of ice, because carbon fines produce grey water and cloudy ice initially. Then write the date on the housing, because an inline filter has no indicator light and lives out of sight behind the appliance, which is precisely how these end up years overdue. Our fridge filter guide covers matching cartridges.
Questions people ask about in line water filter for refrigerator
When is an inline filter better than the fridge's own?
On fridges with no filter bay, on models with expensive or authenticated cartridges, and where a larger element with a longer interval is wanted.
Should I keep the internal filter as well?
Usually not. Two cartridges in series slow the dispenser and double the cost. Fit the manufacturer's bypass plug instead.
Which way round does it go?
With the flow arrow pointing towards the refrigerator, and mounted to the wall or cabinet rather than hanging on the tubing.
How will I remember to change it?
Write the date on the housing. There is no indicator light and it sits out of sight, which is how these end up years overdue.