A water filter in the refrigerator.
Photo: GE

Dryers that don’t dry, vacuum cleaners that don’t clean, and air conditioners that don’t cool may be plagued by the same problem: a clogged or dirty filter. To keep many appliances in tip-top shape, you have to clean or replace a filter. In fact, that’s the first thing to check when something seems awry. When Consumer Reports tests vacuums, air conditioners, dishwashers, and other appliances, filter replacement is one of the things we consider as part of our ease-of-use score.

Any appliance with a filter that cleans air or water needs attention. How often depends on how much you use the appliance and what the manufacturer recommends to get optimal performance. “Some of your appliances are so essential to keeping your home clean that it’s easy to forget that cleaning your appliances should also be part of the annual springtime ritual of scrubbing, polishing, and purging,” the Association of Home Appliance Manufacturers says. Here’s our experts’ advice on the filters you should change or replace and how often:

Filtering Water

Refrigerators
If you have a water dispenser or an icemaker in your refrigerator, you’ll need a filter to remove small particles or contaminants, such as lead and chlorine, and impurities that cause bad tastes or odors. The filters have to be replaced periodically following the guidelines in your owner’s manual, often twice per year. If your refrigerator’s water-supply line uses a filter, replace that, too.

Dishwashers
Dishwashers are equipped with either an automatic filter that grinds food particles so that they wash away with the wastewater or a manual filter that you need to clean yourself. The grinders can be noisy, so quiet dishwashers often have manual filters. They should be cleaned at least every three to six months depending on how often you use your dishwasher. Some manufacturers recommend cleaning the filter every two or three weeks, so check the owner’s manual. “Dirty filters won’t damage a dishwasher but will affect its performance,” says Larry Ciufo, who tests dishwashers for Consumer Reports. Be sure the heating element has cooled down before you reach into the machine.

Water Filters 
Water filters have different life spans depending on the type. Typically, the filter in a carafe water filter is good for 40 gallons. It’s up to you to keep track because few carafe water filters indicate when it’s time to change the filter.

Failing to periodically change the filter can result in water that’s dirtier than before you filtered it. Our water filter ratings include the yearly filter-replacement cost for each model; it ranges from $30 to $180 annually.

Some water filters connect to your water line under the sink or mount on your faucet to filter out sediment, lead, and other contaminants. The filters should be changed periodically, usually after 100 gallons or about four months. Some have built-in indicators that let you know when it’s time. Check the manufacturer’s instructions for your model’s recommended maintenance schedule. The replacement filters range from $40 to $400.

Filtering Air

Air Purifiers
Most air purifiers have a filter indicator (often a light) that alerts you when the filter should be checked and possibly replaced. Though you can simply wipe down most prefilters, the main HEPA filter should be replaced about every six to 12 months, or as your manual advises. We factor this expense—new filters can cost between $50 and $100 or more annually—into the annual costs listed in our air purifier ratings.

More on Indoor Air

Keep in mind that some newer air purifiers will tell you when it’s time to change a filter based on how much you’ve used the unit, and others base their alert on a set number of hours. “So if you run your purifier less often, you should inspect the filter before tossing it to keep from replacing it unnecessarily,” says CR’s Dave Trezza, who oversees our air purifier tests.

Range hoods
Some models have filter maintenance lights; if not, check and clean this filter every one to three months, or more often if you cook frequently. Slide the filter out of the range hood and into a sink filled with hot water and a good degreasing soap. Let it soak for at least 10 minutes. Use a sponge to carefully remove any remaining grease or debris. Then air-dry and reinstall. If a good cleaning doesn’t get the grime off, you’ll need a replacement, which usually costs about $10 to $15.

Over-the-range microwaves
Over-the-range microwaves also have filters that need attention (unlike countertop units, which don’t). A filter with grease buildup results in a fan that can’t exhaust properly or capture cooking fumes, leaving a sticky film on appliances and kitchen walls. To keep it clean, wash the filter in warm, soapy water at least twice a year, more often if you cook at home most nights. Some microwaves have dishwasher-safe filters.

Clothes dryers
A dirty lint filter can extend drying time and lead to lint buildup in the dryer’s cabinet and duct. So in addition to cleaning the lint filter between loads of laundry, also inspect the duct and cabinet every few months to check for lint buildup, which poses a fire hazard. Some newer dryers, such as the Samsung DV56H9100EG, have blocked vent sensors that detect reduced airflow, but not all the sensors performed well in our clothes dryer tests, making a visual inspection the safest bet.

Vacuum cleaners
Failing to change the filters in your vacuum cleaner may cause it to lose suction or worse, spew dust back into the air. Changing the filters regularly, especially on bagless models, saves work and aggravation. Frank Rizzi, who tests vacuums for Consumer Reports, says that every model is very different, so consult the owner’s manual to see how often the filter should be changed and whether it can just be washed instead.

A dehumidifier filter.
Filter for a dehumidifier.

Dehumidifiers
Though your dehumidifier is easy to forget about—especially if it’s out of sight in the basement—most dirty dehumidifier filters can be easily cleaned in just a few minutes rather than replaced. A quick cleaning will improve your air quality and the machine’s performance. This is especially important to do when humidity levels rise above 50 percent, which can lead to the growth of dust mites, mildew, and mold on your filter. (If you see any of these, it’s time for a new one.)

Room air conditioners
All window units have a filter, and many come with a filter indicator that signals when it needs cleaning to keep cooling your home efficiently. If yours doesn’t, check the filter at least once a month during periods of heavy use or year-round if you live in a warm climate. Remove the filter and use your vacuum’s upholstery brush to suck up any heavy dirt, then wash the filter using a mild solution of dishwashing liquid and warm water. Wait until it’s dry to reinsert. “Some filters are easier to remove than others, so consult the owner’s manual for guidance,” says CR’s Christopher Regan, who oversees testing for room air conditioners.

Central air conditioning and heating systems
If you have a combined forced air heating and cooling system, follow the filter manufacturer’s recommendation on how often to change it. In general, the thicker the disposable filter, the less often it needs to be changed. (The models we test last between three and 12 months.) Washable filters usually require monthly cleaning, but “none of the ones we’ve tested have performed very well, so at this point we don’t recommend them,” Trezza says.

Gas furnaces
As with a central AC system, a dirty filter can prevent airflow, leaving the equipment struggling, so replace a disposable one as the manufacturer advises. (Again, most models will need to be changed roughly every three to 12 months.) When you remove the old filter, take note of the size and the arrow that indicates the direction of the airflow; both should be printed on the filter. One of the biggest mistakes people tend to make doing this chore is putting the new replacement filter in backward.

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