How to Install an External (Inline) Filter on a Refrigerator or Ice Maker Line
To install an external refrigerator filter, turn off the cold-water supply, cut the 1/4-inch line, connect the supply side to the port marked INLET and the fridge side to OUTLET, mount the filter, flush it, and re-check for leaks after 24 hours. Use the fittings your filter is made for and the tubing your fridge manual allows, and never use a saddle valve. Replace the filter every 6 months or at its rated gallons. You'll find compatible units in our inline water filter collection.
Before You Start: Fittings, Tubing and Where to Mount
Before you install an external refrigerator filter, match its fittings to your 1/4-inch line, confirm the tubing your fridge allows, and pick a mounting spot where you can change it. Check your water pressure and temperature too. Table 1 shows what each maker allows.
Match the filter's fittings to your 1/4-inch line
Most external refrigerator filters connect to a 1/4-inch water line, but the fitting type varies by filter. The 3M Aqua-Pure IL-IM-01 takes 1/4-inch copper or plastic tubing, while the GE GXRTQR (now discontinued) used a male quick-connect. Check the fitting type printed on your filter before you buy adapters.
Copper, PEX or plastic: what your fridge manual allows
Whirlpool's current manual says copper and PEX tubing from the household line to the refrigerator are acceptable, while GE recommends copper tubing unless you use its GE SmartConnect water line. GE also approves plastic kit lines WX08X10006G and WX08X10015. Follow your own fridge manual, because makers don't agree on one rule.
Table 1 lists the fittings and tubing each manufacturer allows.
Table 1. Fittings and Tubing by Manufacturer
| Fitting / tubing | Who says so | Notes |
|---|---|---|
| 1/4" O.D. copper tubing | Whirlpool, GE | GE recommends copper unless using SmartConnect |
| PEX | Whirlpool (current manual) | Copper and PEX both acceptable |
| GE-approved plastic kit lines | GE | WX08X10006G, WX08X10015 |
| Push-in (collet) fitting, 1/4" copper or plastic | 3M (IL-IM-01) | Install ports as labeled |
| Male quick-connect | GE (GXRTQR, discontinued) | Example of fitting type only |
Behind the fridge or in a nearby cabinet
Mount an external refrigerator filter on the line between the shut-off valve and the fridge, in a spot where you can reach it to change the cartridge. That might be behind the fridge or in a nearby cabinet. Table 2 matches common setups to where the filter goes.
Table 2. Which Setup Fits Your Situation
| Situation | Mount | Note |
|---|---|---|
| Fridge with no built-in filter | On the supply line before the fridge | Filter treats dispenser and ice water |
| Ice machine | On the ice machine's supply line | No softened water to the ice maker (Whirlpool) |
| Second filter ahead of a filtered fridge | On the supply line | Check your manual (see below) |
For an ice machine, see our in line water filter for ice maker options.
Water pressure and temperature limits
Whirlpool says the water pressure at a refrigerator's inlet should be 35–120 psi, and most external filters have their own pressure and temperature limits. The 3M IL-IM-01 is rated to 125 psi maximum, and 3M calls for a pressure limiter above 80 psi. Never connect a filter to hot water; most are rated to 100 °F maximum.
How to Install an External Refrigerator Filter Step by Step
To install an external refrigerator filter, shut off the water and ice maker, cut the line, connect INLET and OUTLET as labeled, and mount the filter upright. The steps below follow the manufacturers' instructions. Follow your filter's own manual where it differs.
Shut off water and the ice maker
Start by turning off the cold-water shut-off valve that feeds the fridge, and turn off the ice maker.
- Close the cold-water shut-off valve to the refrigerator.
- Turn off the ice maker.
- Have a towel ready for water left in the line.
Cut the line and connect inlet and outlet
Cut the 1/4-inch line squarely, then connect the supply side to the filter's INLET port and the fridge side to its OUTLET port. 3M's instructions say to install with the inlet and outlet ports as labeled and make sure not to reverse connections. If your filter has a flow arrow instead, follow the arrow.
- Cut a square section out of the line where the filter will go.
- Connect the supply side to INLET.
- Connect the fridge side to OUTLET.
- On compression fittings, hand-tighten, then turn one more turn; Whirlpool's kit instructions say don't overtighten.
Mount the filter so you can change it
Mount the external filter securely in a spot where you can reach it later to change the cartridge. Keep it away from freezing temperatures; the GE GXRTQR was rated down to 34 °F and the Omnipure K2533 to 35 °F. Use PTFE tape only where your filter's manual says to.
Flush, Leak-Check and First Ice
After installing an external refrigerator filter, flush it with the amount of water its maker specifies, check for leaks right away and again after 24 hours, and discard the first ice. Flush volumes differ by filter, as Table 3 shows.
How much water to flush by filter
Flush an external refrigerator filter with the amount its instructions give, which ranges from about 2.5 to 5 gallons for the filters below. Whirlpool says to flush its fridges 1, 2 or 4 gallons depending on the filter. Without a dispenser, Whirlpool says to discard 3 full containers of ice.
Table 3. Flush Volume by Filter (Maker's Numbers)
| Filter / maker | Flush | Source |
|---|---|---|
| GE GXRTQR (discontinued) | 5 minutes | GE |
| 3M Aqua-Pure AP717 | 2.5 gal (about 5 min) | 3M |
| 3M Aqua-Pure IL-IM-01 | 4 gal (about 8 min) | 3M |
| Omnipure K2533 | 5 gal | Omnipure |
| Whirlpool fridge (new filter or connection) | 1, 2 or 4 gal; no dispenser: discard 3 containers of ice | Whirlpool |
Check for leaks now and again after 24 hours
Check every connection for leaks as soon as you turn the water back on, then check again 24 hours after installation, as GE's instructions advise. Omnipure also says to check for leaks after flushing. A small drip at a compression nut usually means it needs seating, not more force.
Discard the first batches of ice
Discard the first 2–3 batches of ice after connecting a new filter, as Whirlpool's ice-maker kit instructions advise. Whirlpool also says to allow 24 hours for the water to cool. After that, the ice maker should run normally.
Living With an External Filter
Living with an external refrigerator filter means replacing it on schedule, checking whether your fridge's own filter should stay, and watching for low flow. Most problems after an install come from air in the line or a saddle valve.
Replace every 6 months or at the rated gallons
Replace an external refrigerator filter every 6 months or when it reaches its rated gallons, whichever comes first. 3M rates the IL-IM-01 for 2,500 gallons or 6 months and the AP717 for 1,500 gallons or 6 months. The Omnipure K2533 is rated for 1,500 gallons.
Using it with a fridge that already has a filter
If you add an external filter in front of a fridge that already has one, check your manual; Whirlpool's manual recommends the bypass cap when an RO system feeds the fridge. Whirlpool says to remove the fridge filter and install the blue bypass cap in that setup. If you're wondering whether ice maker water goes through the filter, see does ice maker water go through filter.
Low flow or small ice cubes after install
Low flow or small, hollow ice cubes after an install often point to air in the line or a saddle valve. GE says saddle valves can cause small, slow or hollow cubes. For air in the line, see how to bleed air from ice maker line.
Table 4 gathers the limits to check before and after you install.
Table 4. Limits Checklist
| Limit | Value | Source |
|---|---|---|
| Fridge inlet pressure | 35–120 psi | Whirlpool |
| Filter max pressure | 125 psi; limiter above 80 psi | 3M IL-IM-01 |
| Max water temperature | 100 °F | 3M, GE, Omnipure |
| Min water temperature | 34–35 °F (varies by filter) | GE, Omnipure |
| Saddle valve | Don't use | Whirlpool, GE |
| Softened water to ice maker | Avoid | Whirlpool |
| Leak re-check | 24 hours after install | GE |
💡 Editor's Pick
Check your connection type before you buy. Inline filters come with different fittings, so match yours to your water line to make installation easy.
Frequently Asked Questions
Do inline refrigerator water filters work?
An inline refrigerator filter reduces the contaminants it's certified for, so check its certification. For example, the Omnipure K2533 is certified to NSF/ANSI 42 for chlorine. NSF's guide to NSF/ANSI 42, 53 and 401 explains that NSF/ANSI 42 covers aesthetic claims such as chlorine, taste and odor.
Can I use a saddle valve for the ice maker line?
No, Whirlpool and GE both advise against saddle valves for refrigerator and ice maker lines. Whirlpool says not to use a piercing-type or 3/16-inch saddle valve. GE says saddle valves are not recommended and can cause small, slow or hollow ice cubes. Follow local plumbing code.
Which direction does an inline filter go?
An inline filter goes with the water supply connected to the port marked INLET and the fridge connected to OUTLET. 3M's instructions say to install the ports as labeled and not to reverse connections. If your filter has a flow arrow instead, point it toward the refrigerator.
Can I connect an ice maker to softened water?
Whirlpool advises against sending softened water to the ice maker. Connect the ice maker line to a cold-water supply that isn't softened. Check your refrigerator manual for its water supply requirements before you install a filter or tap a new line.
How often should I change an inline refrigerator filter?
Change an inline refrigerator filter every 6 months or when it reaches its rated gallons, whichever comes first. 3M rates the IL-IM-01 at 2,500 gallons or 6 months and the AP717 at 1,500 gallons or 6 months. Flush each new cartridge per its instructions.
Sources
- NSF, NSF/ANSI 42, 53 and 401: Filtration Systems Standards
- Whirlpool owner's manual W11304737; Whirlpool Product Help, How to Flush the Water System; Whirlpool ice-maker kit WPW10315447 instructions
- GE Appliances support articles 18959 and 19600; GE Parts GXRTQR; GE under-sink manual 49-50057
- 3M Aqua-Pure IL-IM-01 and AP717 manuals
- Omnipure K2533 specification sheet