Water Filters and Water Filtration: A Beginner’s Guide
Water filters can improve the taste, smell, appearance, or quality of water, but choosing the right one requires more than simply selecting a popular brand. Water filtration systems use different methods, and no single filter is designed to remove every possible contaminant.
The best place to begin is by testing your water and identifying what you want the filter to accomplish.
Quick Answer
Water filtration may take place at a single faucet or where the main water line enters a building. Pitchers and faucet filters provide basic drinking-water filtration, while under-sink systems offer greater capacity. Reverse-osmosis systems provide more specialized treatment, and whole-house filters treat water throughout the home.
Always compare the exact model’s certified reduction claims before buying.
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What Is Water Filtration?
Water filtration is the process of passing water through a material or treatment system to reduce selected particles, chemicals, tastes, odors, or other unwanted substances.
Common filtration and treatment methods include:
- Sediment filtration
- Activated-carbon filtration
- Ceramic filtration
- Reverse osmosis
- Ion exchange
- Ultraviolet treatment
- Specialized contaminant-reduction media
These technologies accomplish different jobs. For example, a sediment filter can capture rust, sand, and visible particles, while activated carbon is commonly used to reduce chlorine taste and odor.
A water softener reduces hardness minerals but should not be considered a replacement for every other type of water filter.
Test Your Water First
Before buying a filter, determine what is actually in your water.
Customers using municipal water can begin by reviewing their water utility’s annual Consumer Confidence Report. Additional tap testing may be useful when older plumbing, service lines, or household fixtures are a concern.
Private-well owners should arrange appropriate laboratory testing because they are responsible for monitoring and maintaining their water supply.
Read How to Test Your Water Before Buying a Filter before selecting a filtration system.
Types of Water Filters
Water-Filter Pitchers
Pitcher filters are affordable, portable, and easy to use. They are generally best for households that only need a limited amount of filtered drinking water.
Their disadvantages include limited capacity, slower filtration, and frequent cartridge changes.
Faucet-Mounted Filters
A faucet-mounted filter attaches to a compatible kitchen faucet. It provides filtered water without filling a separate pitcher, but it may reduce water flow and will not fit every faucet.
Under-Sink Water Filters
An under-sink filter is installed beneath the kitchen sink. It normally provides greater capacity and faster filtration than a pitcher.
Some systems use the existing faucet, while others require a separate drinking-water faucet. Installation requirements vary considerably among models.
Compare water filters for your home on Amazon →
Reverse-Osmosis Water Filtration
A reverse-osmosis system normally includes sediment and carbon stages along with a semipermeable membrane. Most residential systems are installed beneath the kitchen sink and provide treated water through a dedicated faucet.
RO systems can reduce a broad range of dissolved substances, but buyers must examine the exact model’s verified reduction claims. They also require filter and membrane replacements, installation space, a drain connection, and some reject-water production.
Read Reverse Osmosis vs. Whole-House Filtration: Which Do You Need? for a complete comparison.
Whole-House Water Filtration
A whole-house system is installed where water enters the home. Depending on its treatment media, it may address sediment, chlorine taste and odor, iron staining, sulfur odors, or other confirmed problems.
These systems must be sized according to the home’s peak water demand, plumbing size, water pressure, and tested water conditions.
Read our Whole-House Water Filters guide before comparing point-of-entry systems.
How to Choose a Water Filter
Start by deciding where you need treated water. If you only want filtered drinking and cooking water, a point-of-use system may be sufficient. A whole-house system is more appropriate when the water problem affects showers, laundry, fixtures, or appliances throughout the property.
Before buying, compare:
- The contaminants the exact model is certified to reduce
- Filter capacity and flow rate
- Replacement-filter prices
- Recommended replacement intervals
- Installation requirements
- Available space
- Water and electricity use
- Warranty and replacement-part availability
Understanding Water-Filter Certifications
Do not assume a certification logo means that a filter removes every contaminant. Verify the certification for the exact model and the specific reduction claim.
Common standards include:
- NSF/ANSI 42: Certain aesthetic effects, such as chlorine taste and odor
- NSF/ANSI 53: Specific contaminants that may have health effects
- NSF/ANSI 58: Point-of-use reverse-osmosis systems
- NSF/ANSI 55: Ultraviolet microbiological water-treatment systems
A filter certified under one standard does not necessarily carry every reduction claim covered by that standard.
For additional guidance, read the EPA WaterSense Guide to Selecting Water Treatment Systems. Set this external link to open in a new tab.
Replace Filters on Schedule
A neglected water filter can lose effectiveness, reduce water flow, or develop other problems. Follow the manufacturer’s replacement schedule and use the correct cartridge for your model.
Replacement timing may depend on water use, water quality, filter capacity, and the manufacturer’s instructions.
Compare replacement water-filter cartridges on Amazon →
Final Thoughts
A water filter should be selected according to tested water conditions, intended use, verified reduction claims, capacity, and long-term maintenance costs.
Test your water first. Then decide whether you need filtration at one faucet or throughout the building. Compare the exact models and certifications instead of relying only on broad advertising claims.
Water conditions vary. This educational article does not replace laboratory testing, local health guidance, or advice from qualified water-treatment and plumbing professionals.