How to Change a Water Filter: All 4 Types

Q: How Long Should You Run Water After Changing a Filter?

Run a new filter for 3 to 5 minutes ( source ), or about 2 to 3 gallons, before you drink from it. Fresh carbon media sheds harmless carbon fines, the black specks you may spot in the first pour, and the flush clears them along with any trapped air. Larger reverse osmosis, whole-house, and under-sink systems can need a longer flush, so follow the cartridge instructions.

Clean water should taste like nothing at all. When the flow slows to a trickle or a metallic tang creeps in, the filter has stopped pulling its weight and needs to come out.

The exact steps change from one system to the next, but the logic stays the same across all of them. You cut the water, open the housing, swap the cartridge, and flush before you drink. This guide walks through that process for the four filters most homes run.

Whether you have a whole-house tank in the garage or a pitcher in the fridge door, the steps below get clean water flowing again.

Key Takeaways

Identify your system first: Whole-house, under-sink, refrigerator, and pitcher filters each change differently, so confirm which type you have before you start.
Match the replacement: Buy the exact size and micron rating your housing needs, and check for an NSF/ANSI mark (42 for taste and odor, 53 for lead and cysts).
Shut off and depressurize: Turn off the water and open a faucet to release trapped pressure before unscrewing any whole-house or under-sink housing.
Flush before you drink: Run a new carbon filter for 3 to 5 minutes to clear loose carbon fines and trapped air.

In This Article

Water Filter Options
Change Whole House Filter
Change Refrigerator Filter
Change Under-Sink Filter
Change Water Pitcher Filter
FAQs
Conclusion

Water Filter Options

When you are buying a water filter, you generally choose between four main categories based on your needs.

These common systems include:

Whole house: Filters water at the entry point for the entire home.
Refrigerator: Built-in units for chilled water and ice makers.
Under the sink: Dedicated filtration for a specific kitchen faucet.
Pitcher: Portable, countertop filtration for drinking water.

Each type requires a slightly different approach for maintenance. We cover the specific steps for each below.

Before you buy any replacement, match it to the job. NSF/ANSI 42 certifies a filter for aesthetic issues like chlorine, taste, and odor, while NSF/ANSI 53 certifies it for health-related contaminants such as lead and parasitic cysts ⁽¹⁾. If lead is your worry, a 53-certified cartridge is the one to look for.

How to Change a Whole House Water Filter

A whole house water filter is the workhorse of your plumbing system. Because it handles high volume and pressure, it takes a bit more effort to change. Follow these steps to swap it out safely.

1. Gather Your Tools

You want everything within reach before you shut off your water.

Grab these essential items before you start:

Replacement filter: Confirm you have the correct micron rating, size, and NSF/ANSI certification for your housing.
Filter wrench: This plastic loop tool usually comes with the unit and gives you leverage to unscrew the housing.
Strap wrench: If the housing is stuck, a rubber strap wrench provides extra grip without cracking the plastic.
New O-ring: These rubber seals degrade over time, so replacing them with every filter change prevents leaks.
Food-grade silicone grease: This lubricates the O-ring for a watertight seal.
Bucket and towels: Water spills when you open the housing, so be ready to catch the runoff.

2. Shut Off the Water Supply

Locate the shut-off valve nearest to your filter system. Rotate the handle to the “off” position.

If your filter does not have a dedicated isolation valve, turn off the main water supply to the house. It is safer to cut the main supply than to fight a pressurized leak.

Top Tip

Fill a bucket with water before you shut off the main supply. You will need this water to clean the filter housing later in the process.

3. Depressurize the Plumbing

Even with the water off, pressure stays trapped in the pipes. If you open the filter now, water sprays everywhere.

Open a nearby faucet or bathtub tap on the lowest floor of your home. Let the water run until it stops completely. This releases the pressure and makes unscrewing the filter housing much easier.

4. Isolate the Filter

If your system has a three-valve bypass setup, adjust the levers now.

Turn the “inlet” and “outlet” valves to the closed position. If you have a “bypass” valve, open it. This lets water flow through the house unfiltered while you work on the unit. If you do not have a bypass valve, simply keep the main water supply off.

Keep In Mind

Old plumbing can be tricky. If valves feel stuck, do not force them. It is better to call a plumber than to snap a rusted valve stem.

5. Unscrew the Filter Housing

Place a bucket directly under the filter sump. Slide the plastic filter wrench over the housing and turn it to the left (counter-clockwise).

If the housing will not budge, look for a red pressure-relief button on top of the unit. Press it to release any final vacuum seal. If it is still stuck, use a strap wrench or tap the handle of your plastic wrench gently with a rubber mallet.

Hard water creates scale that acts like glue. Be patient and use steady force to avoid cracking the canister.

6. Remove and Inspect

Lower the housing carefully, as it will be heavy with water. Dump the old water and pull out the used filter cartridge.

Inspect the bottom of the housing. If you see a thick layer of sludge or sediment, your water supply might have high turbidity. Clean the inside of the housing with warm, soapy water and a soft brush. Rinse it thoroughly with the clean bucket water you saved earlier.

Check Before You Change

If your filter is slimy or black with mold, you may need to sanitize the system with a mild bleach solution. Check your manufacturer’s manual for specific sanitation instructions.

7. Swap the O-Ring

The O-ring is the black rubber band that seals the housing to the cap. Pry the old one out carefully using a flat tool or your fingers.

Wipe the groove clean with a cloth. Coat the new O-ring in a light layer of food-grade silicone grease. Set it into the groove and make sure it sits flat. Do not use Vaseline or petroleum jelly, as these can cause the rubber to swell and leak.

8. Install the New Filter

Place the new filter cartridge into the housing. Make sure it centers perfectly on the “standpipe” at the bottom.

Screw the housing back onto the cap by hand. Once it is hand-tight, use the filter wrench to snug it just a bit more. Do not overtighten, or you will crack the housing or make it impossible to remove next time.

9. Turn the Water Back On

Close any faucets you opened to drain the system. Slowly open the inlet valve to the filter. You will hear water rushing in.

Check for leaks immediately. If water drips from the housing threads, tighten it slightly with the wrench. Once the system is pressurized and leak-free, open the outlet valve and close the bypass valve.

How to Change a Refrigerator Water Filter

A refrigerator water filter keeps your ice cubes clear and your water dispenser tasting fresh. When the indicator light turns red, it is time to swap it out.

Most fridges use either a push-in filter (usually inside the fridge) or a twist-in filter (usually in the bottom grille).

1. Locate the Filter

Check your owner’s manual to find the filter location.

Common locations include:

Top right corner: Inside the refrigerator compartment.
Bottom grille: Underneath the doors near the floor.
In the door: Sometimes hidden behind a shelf bin.

2. Remove the Old Unit

For push-button models, press the release button firmly until the filter pops out. Pull it straight out.

For twist-in models, rotate the knob counter-clockwise a quarter turn until it releases, then pull it straight out. You do not usually need to turn off the water supply for fridges, as they have automatic shut-off valves built into the filter mount.

3. Click the New One In

Remove the protective cap from the new filter. Align it with the housing and push it in until it clicks, or twist it clockwise until it locks.

Flush the system by running two to three gallons of water through the dispenser. This clears air bubbles and loose carbon dust. Finally, press and hold the “reset filter” button on your fridge panel for 3 to 5 seconds to reset the indicator light.

How to Change an Under-Sink Water Filter

Under-sink water filters provide high-quality water for cooking and drinking. These systems often have multiple stages, so pay attention to which cartridges go in which slot.

1. Shut Off the Cold Line

Turn off the cold water supply valve located under the sink. Open the dedicated filtered water faucet to release pressure.

2. Unscrew the Housings

Place a towel under the unit. Unscrew the filter housings using the provided wrench. If you have a “quick-change” system, simply twist the cartridges off by hand.

3. Clean and Replace

Remove the old cartridges. Scrub the inside of the housings with soapy water and rinse well. Insert the new filters, seating the rubber gaskets correctly.

Screw the housings back on. Hand-tighten them, then give a slight turn with the wrench.

4. Flush the System

Turn the water supply back on slowly. Check for leaks. Let the filtered faucet run for 5 to 10 minutes. This activates the carbon and flushes out any fines.

How to Change a Water Pitcher Filter

Pitcher filters are the easiest to maintain but need the most frequent changes.

1. Remove the Old Filter

Pull the old filter cylinder out of the reservoir and discard it. Wash the pitcher and reservoir with warm, soapy water to remove any biofilm or algae.

2. Prime the New Filter

Read the instructions on the wrapper. Some filters need to soak in cold water for 15 minutes. Others just need a quick rinse under the tap.

3. Insert and Flush

Push the new filter into the reservoir until it seals tightly. Fill the pitcher with water and pour it out (or water your plants with it). Repeat this twice. This clears out carbon dust so your drinking water runs clear. Reset the electronic timer or calendar dial on the lid.

FAQs

How Often Should You Replace a Water Filter?

Replace most filters on a schedule: pitcher filters every 2 months, refrigerator and under-sink cartridges every 6 months, and whole-house cartridges every 3 to 6 months. Track gallons too, not just the calendar. Under-sink granular carbon cartridges are rated for roughly 500 to 750 gallons ⁽²⁾. A lead-certified carbon block can let lead break through abruptly once it hits its rated capacity ⁽³⁾. If pressure drops or the taste turns, change it right away regardless of the date.

What Happens if You Don’t Replace a Water Filter?

A neglected filter clogs with trapped debris, which chokes your water pressure down to a trickle. Worse, a saturated cartridge stops trapping contaminants and can let sediment, chlorine byproducts, or lead pass straight through. The filter media can also become a home for bacteria, so the water leaving it may be dirtier than the water going in.

Can Unfiltered Water Make You Sick?

Unfiltered tap water can make you sick, though municipal supplies are treated and usually safe to drink. The bigger risks are lead leaching from old pipes, leftover chlorine, or parasitic cysts like Giardia. Private well water carries a higher chance of bacteria and nitrates, so test and filter it rather than trusting it by taste.

How Much Does a Water Filter Cost?

A replacement water filter runs anywhere from about $5 to $100, depending on the system. Pitcher cartridges are the cheapest, usually $5 to $15. Under-sink and refrigerator filters land around $30 to $60. Large whole-house cartridges range from $20 to $100 based on their micron rating and material.

How Long Should You Run Water After Changing a Filter?

Run a new filter for 3 to 5 minutes ⁽⁴⁾, or about 2 to 3 gallons, before you drink from it. Fresh carbon media sheds harmless carbon fines, the black specks you may spot in the first pour, and the flush clears them along with any trapped air. Larger reverse osmosis, whole-house, and under-sink systems can need a longer flush, so follow the cartridge instructions.

Why Is My Water Cloudy After Changing a Filter?

Cloudy water after a filter change is almost always harmless air, not contamination. A new cartridge forces thousands of tiny air bubbles into the line, and they clear on their own if you let a full glass sit for a minute. The milky look disappears completely once the filter has run for a day or two.

Can You Get Sick From Not Changing Your Water Filter?

Yes, an overdue filter can make you sick because bacteria can multiply inside a saturated cartridge. The CDC notes that once a filter strips out chlorine or other disinfectants, more germs can grow in the plumbing behind it, which is why cartridges must be swapped on the maker’s schedule ⁽⁵⁾. A filter left in for years can then shed that buildup back into your glass.

Why Do Water Filters Turn Brown?

Water filters turn brown because they are trapping exactly what you want out of your water. The color comes from captured sediment, rust, iron, and pipe grime building up in the media. A deep brown or black cartridge is fully loaded and should be replaced, since it has little capacity left to catch anything new.

What Is the Best Filter for Drinking Water?

The best drinking water filter is one certified for the contaminants in your supply, and a reverse osmosis system covers the widest range. The APEC Water Systems ROES-50 Essence Series is a popular under-sink pick that reduces lead, chlorine, fluoride, and dissolved solids. Whatever you choose, look for an NSF/ANSI 53 certification, which verifies the filter cuts health-related contaminants like lead rather than just improving taste.

What Do NSF/ANSI 42 and 53 Certifications Mean?

NSF/ANSI 42 and 53 are the two main certifications for drinking water filters, and they cover different problems. A 42 mark means the filter is verified to reduce aesthetic issues like chlorine, taste, and odor. A 53 mark means it reduces health-related contaminants such as lead and cysts; certified units are tested against challenge water holding 150 ppb of lead, ten times the EPA action level, and the standard now caps filtered lead at 5 ppb. Check the box for the standard that matches your water.

Do Unused Water Filters Expire?

Unused water filters do not expire as long as they stay sealed in the original packaging and dry. The exception is a cartridge with a pre-lubricated O-ring: after several years the silicone grease can dry out and crack, which may cause the housing to leak when you finally install it. Store spares away from heat and humidity to keep them ready.

In Conclusion

Swapping a water filter takes minutes once you know where the housing is and which way it turns. A little prep, the right cartridge, and a good flush are all that stand between you and clean water.

Stay ahead of it. Do not wait for the taste to sour or the pressure to drop. Note the change date on your calendar or set a phone reminder so the filter never runs past its capacity.

Match the replacement to your system, watch for leaks when you turn the water back on, and you will keep sediment, chlorine, and other contaminants out of every glass.

Feedback: Was This Article Helpful?

Thank You For Your Feedback!

What Did You Like?

What Went Wrong?