How to Choose a Water Filter

Choosing the right water filter for your home is important for protecting your health and improving water taste and odor. With so many different types of water filters on the market, it can be overwhelming to decide which is best for your needs. This comprehensive guide provides tips on the key factors to consider when selecting a water filtration system.

Types of Water Filters

There are several broad categories of water filters, each with pros and cons. Understanding the different technologies will help you zero in on the right system for your household.

Pitcher Filters

Pitcher style filters, like Brita, are popular for their convenience and low cost. They consist of a plastic pitcher with a filter cartridge inside. Simply fill the pitcher with tap water and allow it to pass through the filter into the container. The filters use activated carbon to remove contaminants like lead, copper, and chlorine.


  • Inexpensive initial purchase ($15-$60)
  • Easy to use and maintain
  • Good for small households
  • Reduce chlorine taste and odor
  • Provide basic filtration for contaminants


  • Filters need frequent replacement (every 40 gallons or 2 months)
  • Limited filtration – don’t remove major contaminants
  • Slow flow rate (fills about 1-2 cups per minute)
  • Small capacity

Faucet Filters

Faucet filters attach directly to the kitchen faucet. They are similar to pitcher filters but offer the convenience of filtered water on demand. Carbon filtration removes chlorine, sediments, and some heavy metals.


  • Low upfront cost ($15-$30)
  • Easy installation and use
  • Provide filtered water on demand
  • Reduce chlorine odor/taste
  • Take up little counter space


  • Must be replaced often (every 100 gallons or 3 months)
  • Only filter one faucet
  • Don’t remove major contaminants
  • Can reduce water flow

Under Sink Filters

Under sink water filters are mounted below the sink and connected to the main water supply line. This allows them to filter all the water entering the sink. Most use a multi-stage filtration system with carbon filters plus an additional technology like reverse osmosis.


  • Provide whole house or sink-specific filtration
  • Multi-stage filtration removes wide range of contaminants
  • Don’t take up counter space
  • Last 6-12 months before filter change


  • Higher upfront cost ($100-$500)
  • expert installation often required
  • More frequent filter changes than whole house systems
  • Ongoing maintenance

Whole House Filters

Whole house filtration systems filter all the water entering a home. They are installed on the main water line where it enters the house. This provides filtered water to all faucets and appliances. Systems use a combination of sediment filters, activated carbon, and other media.


  • Filter all water in the home
  • Remove a wide range of contaminants
  • Long filter life (6-12 months)
  • Low maintenance after installation


  • High upfront installation cost ($500-$2,000)
  • Professional installation required
  • Large units require space for installation
  • Don’t remove all heavy metals

Reverse Osmosis Systems

Reverse osmosis (RO) uses pressure to force water through a semipermeable membrane that traps contaminants. This intensive multi-stage filtration removes sediments, chlorine, heavy metals, bacteria, and more. RO can be used for whole house or under sink applications.


  • Remove the widest range of contaminants
  • Improve water taste and odor
  • Under sink units don’t take up space


  • Waste 3-10 gallons of water for every 1 filtered gallon
  • Require drain connection to dispose of wastewater
  • Under sink models provide limited filtered water
  • RO membranes need annual replacement

Water Softeners

Water softeners are not technically filters since they do not remove contaminants. However, they are important for treating hard water caused by high levels of calcium and magnesium. Water softeners exchange hardness minerals for sodium ions to prevent scale buildup.


  • Prevent spotting and mineral scale on fixtures
  • Allow soap and detergents to lather better
  • Improve feeling of softened water on skin
  • Inexpensive salt recharges every 1-2 months


  • Do not remove other water contaminants
  • Add sodium to water which some try to avoid
  • Ongoing purchase of salt pellets
  • Possible installation complications

Prioritize Your Water Filter Needs

Choosing the right type of filtration system starts with identifying your specific water purification requirements. Consider aspects like:

  • Water source – Well water or municipal supply? Municipal water is treated but may still contain chlorine and other contaminants. Well water often has high sediment and hardness levels.
  • Water quality – Have you tested your tap water? Typical municipal water reports indicate levels of chlorine, fluoride, sediments and major contaminants. Well water testing provides a breakdown of contaminants.
  • Water uses – Do you want to filter shower water, consume filtered drinking water, or both? This impacts system selection.
  • Problem contaminants – Are you trying to remove a specific contaminant like lead, arsenic, or chlorine? Or just improve general taste and odor?
  • Household size – Do you need a system that can handle the demands of a large family versus just one or two people?

Once you know your specific water filtration goals, you can narrow down the choices and select the right system. Common priorities include:

  • Removing chlorine taste and odor
  • Reducing lead and heavy metals
  • Filtering out sediment from well water
  • Improving water taste and clarity
  • Eliminating bacteria and microorganisms
  • Softening hard water buildup
  • Purifying well water for safety

Make a list of your primary water purification needs before shopping for a filter. This ensures the system you select can handle your specific requirements.

Filtration Technology Comparison

Sediment Filters

Sediment filters use a physical barrier to trap suspended particles in water. Filtration ratings are measured in microns – the smaller the micron size, the smaller the particles captured.

Micron Sizes

  • 50 microns – Traps sand, silt, sediment
  • 20 microns – Removes majority of sediment particles
  • 5 microns – High filtration for sediment, rust, algae
  • 1 micron – Submicron filtration for finest sediment
  • Less than 1 micron – Extremely fine filtration

Sediment pre-filters protect other filter media from clogging prematurely. They help remove particles that cause water cloudiness.

Activated Carbon Filters

Activated carbon filtration utilizes highly porous carbon that attracts and traps contaminants. It effectively reduces chlorine, pesticides, industrial solvents, bad taste and odors. Carbon filters need regular replacement when saturated.

Types of activated carbon:

  • Granulated Activated Carbon (GAC) – Most common carbon used in water filters. Effective at trapping organic chemicals.
  • Block Carbon – Carbon fused into a uniform block. Provides extremely high surface area for contaminant removal.
  • Catalytic Carbon – Impregnated with other materials like copper or zinc to facilitate chemical reactions that destroy contaminants. Good for removing chlorine.

Ion Exchange Resins

Ion exchange resins swap ions in the water for harmless ones they are holding. This is used in water softeners to exchange calcium and magnesium ions for sodium.

Other uses include:

  • Perchlorate removal – swaps perchlorate ions for chlorine ions
  • Nitrate removal – exchanges nitrate for chloride ions
  • Heavy metal removal – replaces heavy metal ions with sodium or hydrogen

The exchange capacity depends on the resin. Once exhausted, brine solution regenerates the resins.

Reverse Osmosis

Reverse osmosis forces water through a semipermeable membrane under high pressure. The membrane blocks contaminants while allowing water to pass through. It effectively removes:

  • Particles larger than water molecules
  • Dissolved salts, metals, minerals
  • Viruses and bacteria
  • Chemicals like pesticides, detergents, dyes

Disadvantages include water waste and membrane fouling. Pre-filters extend membrane life.

Ultraviolet Disinfection

Ultraviolet (UV) light destroys microorganisms by damaging their DNA and rendering them unable to reproduce. It provides effective disinfection without chemicals.

UV light has germicidal properties at wavelengths around 260 nm. UV disinfection limits include:

  • No residual disinfectant effect
  • Turbid water can shield microbes from UV exposure
  • Organic particles can absorb UV light
  • Only treats small volumes of water at once

Ozone Disinfection

Ozone is an unstable gas (O3) that reacts with microbes and oxidizes contaminants. As a disinfectant, it destroys bacteria 3,000 times faster than chlorine.

Advantages of ozone water treatment:

  • Effective broad-spectrum disinfectant
  • Eliminates viruses, bacteria, protozoa, fungi
  • Breaks down pesticides, detergents and other chemicals
  • Produces no toxic byproducts

The unstable nature of ozone means it quickly reverts back to oxygen leaving no residual in water.

Important Water Filter Certifications

There are independent testing organizations that certify the safety and performance of water treatment products. Look for these certification marks when comparing water filters:

NSF International

NSF International is the main certification body for water treatment units. NSF/ANSI standards establish minimum requirements for materials, contaminant reduction and structural integrity.

Relevant NSF certifications:

  • NSF/ANSI 42 – Certifies aesthetic contaminant reduction (chlorine, taste, odor, particulates).
  • NSF/ANSI 53 – Certifies health contaminant reduction (lead, VOCs, cysts, asbestos).
  • NSF/ANSI 58 – Validates performance of reverse osmosis drinking water systems.
  • NSF/ANSI 44 – Certification for water softeners and their safety.

Water Quality Association (WQA)

The WQA provides product certifications for home water treatment equipment. Testing validates claims of contaminant reduction.

Look for WQA certifications on:

  • Reverse osmosis systems
  • Distillers
  • Water softeners
  • Scale and deposit controllers
  • Ultraviolet systems

Underwriters Laboratories (UL)

UL safety certifications apply to the electrical and structural components of water filters. Relevant UL classifications for water treatment products include:

  • UL 979 – Ozone generators
  • UL 499 – Drinking water treatment units
  • UL 1081 – Drinking water unit electrical systems
  • UL 61800-6 – UV water purifier electrical systems

Determine Your Budget

The upfront cost of a water filtration system can range from $20 for a basic pitcher filter to $2,000 or more for a whole house system. Ongoing maintenance and filter replacement is another cost factor.

Typical price ranges by type:

  • Pitcher filter – $15 – $60
  • Faucet filter – $15 – $80
  • Under sink system – $100 – $500
  • Whole house system – $500 – $2,000
  • Reverse osmosis system – $200 – $3,000
  • Water softener – $400 – $2,500

When determining your budget consider:

  • Upfront cost of filters and installation
  • Filter replacement frequency and cost
  • Special installation requirements
  • Added features like water softening, UV, RO
  • Maintenance costs over 5-10 years

Look for systems with a lower total cost of ownership. Extended filter life, DIY installation and multi-stage filtration in one system help minimize long-term costs.

Setting a budget before shopping makes it easier to target affordable systems that meet your purification needs.

Key Contaminants to Remove

Common water contaminants that home water filters help reduce include:

Particulates and Turbidity

Particles that make water appear cloudy or colored. Caused by soil sediments, organic debris, sand, minerals. Removed by sediment filters.

Chlorine and Chloramines

Added to public water supplies as a disinfectant. Cause bad tastes, odors. Carbon filters help reduce them.


Naturally occurring or added to water for dental health. Can cause staining, bone issues at high levels. RO removes some fluoride.

Hard Water Minerals

Excess calcium, magnesium cause limescale buildup on fixtures and appliances. Water softeners reduce these ions.

Heavy Metals

Lead, mercury, arsenic, cadmium. Health risks even at low levels with long-term exposure. RO and specialty media (like KDF) help lower heavy metals.


Bacteria, viruses, protozoa and other pathogens. Can contaminate well water or municipal lines through leaks. Disinfection by UV, ozone, or chlorine kills most microbes.

Organic Compounds

Pesticides, herbicides, industrial solvents and chemicals. Carbon block filters help reduce many volatile organic compounds.


Radioactive gas dissolved in groundwater that can enter air in households at unsafe levels. Granular activated carbon adsorption or aeration removes dissolved radon gas.

Consider which of these are concerns in your water when selecting a filtration system.

Maintenance Requirements

To keep water filters working properly requires replacing filters and cleaning certain components. General maintenance tasks include:

Replacing filter cartridges – Most systems require new filters every 6-12 months. Faucet and pitcher filters may need replacement every 2-3 months.

Cleaning UV bulbs – Hard water deposits or iron can coat UV bulb quartz sleeves. Periodic cleaning restores maximum UV effectiveness.

Sanitizing the system – Disinfecting with chlorine flush helps prevent biofilm buildup in filters and plumbing lines.

Checking water quality – Periodic water tests help confirm the system is performing and determine when to replace filters.

Monitoring usage – Tracking water throughput or time in use ensures filters are replaced at recommended intervals.

Checking for leaks – Inspect seals, connections and housing O-rings for any water leaks with under sink and whole house systems.

Select a filtration system that makes maintenance easy through quick cartridge changes, filter life indicators and automated operation features.

Special Installation Requirements

Some types of water filters have additional installation considerations:

Under sink systems – Require connecting to the household plumbing and providing filtered water faucet. May need electrical outlet for units with UV, RO or meters.

Whole house filtration – Typically installed near main water line entering home. Complex plumbing connections and potentially electrical or drain lines. Should be done by contractors.

Water softeners – Install on main water supply before branches to household plumbing. Need nearby drain for brine discharge during regeneration. Require salt storage.

Reverse osmosis – In addition to water supply/drain connections, under sink RO needs space for storage tank and may need new faucet.

Iron removal – Oxidizing filters require backwashing to regularly clean filter media. Need drain connection and space for backwash discharge.

Review installation needs before purchasing a system. Inclusion of all connection accessories and professional installation can simplify the process.

Top Brands of Water Filters

Leading water filter companies known for quality include:


Best known for durable stainless steel gravity-fed filters. Systems available in sizes for travel, household and emergency preparedness.


Specialize in whole house water softeners, sediment filters and carbon tank systems for well water.


Provider of under sink, shower head, whole house filters. Known for chloride removal.


Manufacturer of leading reverse osmosis water filters and membrane technologies.


Major supplier of water softeners along with under sink and whole house filtration systems.


An innovator in water softeners and non-electric home water filtration appliances.


Makes producer of seven-stage reverse osmosis systems and alkaline drinking water systems.

When selecting a water filtration unit, consider sticking with an established brand with proven performance and certifications.

System Sizing Considerations

Make sure to size your water filter properly for your household needs:

Water Usage

Estimate the typical daily water usage for your home in gallons to size the system capacity. Average indoor water use is 50-100 gallons per person daily.

Water Pressure

Standard household water pressure ranges from 40-80 psi. Filters and membranes have minimum/maximum pressure requirements.

Water Flow Rate

Measure water flow from your main supply line in gallons per minute. Flow rates around 5-8 gpm are typical.

Household Size

Number of occupants impacts the required system capacity. Consider both current and future needs.

Peak Demand

Determine peak usage periods – like mornings when multiple showers occur – to ensure the system can handle maximum demand.

With capacity that meets your specific household’s requirements, the water filter will deliver consistent performance.

Saving Water with Filtration

Water filters can also help save water in several ways:

Eliminate bottled water – Drink filtered tap water instead of bottled water to save the water required in manufacturing and transporting plastic bottles.

Shorten flushing time – With filtered water, spend less time running the faucet waiting for cold, clear water.

Enable rainwater use – Filtration allows harvested rainwater to be used indoors for drinking and cooking.

Recycle RO wastewater – Collect the reject water from reverse osmosis systems to use for watering plants.

Spot treat problem faucets – Install faucet filtration only where needed rather than whole house.

Conserve filtered water – Remember that filtered water