How to Choose a Water Filter?

Filtered water is broadly used for drinking, cooking, and other purposes in daily life. However, water quality varies depending on its source, and different household uses may have different filtration requirements.

Choosing the right water filter therefore starts with two questions: What contaminants are present in the water, and what level of filtration does the intended application require? This guide explains the key factors to consider when selecting a water filter for your household.

Understand Your Water Source and Water Quality

Different water sources tend to contain different types of contaminants. Identifying where your water comes from and what may be present in it is therefore the first step in determining the required level of filtration.

Municipal Water

Municipal water is treated before distribution and is generally suitable for daily use. However, it may still contain chlorine used for disinfection, sediment, rust from aging pipes, or substances that cause an unpleasant taste and odor. The specific water quality may also vary depending on local treatment methods and the condition of the distribution system.

You can review the water quality report provided by the local supplier to identify the substances commonly found in the water. You can then use this information, together with any noticeable taste, odor, or sediment issues, to determine the required level of filtration.

Groundwater and Well Water

Groundwater and well water often contain dissolved minerals because the water passes through soil and rock layers before it is collected. Depending on local geological and environmental conditions, it may contain heavy metals or minerals such as calcium and magnesium that contribute to hard water. It may also contain bacteria, viruses, parasites, or other microorganisms, particularly if the well or surrounding area is contaminated.

If your household uses a private well, arrange for the water to be tested by a qualified laboratory. The test should cover microorganisms, minerals, and contaminants associated with local geological conditions or other possible sources of pollution. Additional testing may be needed if the water changes in taste, odor, color, or clarity, or after flooding or repairs to the well.

Rainwater

Rainwater is used as an alternative water source in some regions. Although it generally contains fewer dissolved minerals, bacteria, microorganisms, and organic contaminants may enter the water during collection or storage. Its quality can be affected by the collection surface, storage tank, and maintenance conditions.

Inspect the roof, gutters, filters, and storage tank for accumulated debris, animal waste, insects, or other possible sources of contamination. If the rainwater will be used for drinking or cooking, have it tested by a qualified laboratory for microorganisms and relevant chemical contaminants. The inspection and test results can then help determine whether sediment filtration, disinfection, or additional treatment is required.

Match Filter Cartridges to Your Water Quality Needs

After identifying the water quality concerns, the next step is to select filter cartridges designed to address the relevant contaminants. A water purification system may use three or more cartridges in sequence, with larger particles removed first before the water passes through finer filtration stages. This staged filtration approach can help protect downstream cartridges and extend their service life.

Polypropylene (PP) Sediment Filter

A PP sediment filter is commonly used as the first stage of filtration. It removes larger suspended particles such as sand, dust, sediment, and rust. This stage is particularly useful for groundwater, well water, or municipal water delivered through aging pipes.

Sediment filtration can improve the clarity of water used for washing, cleaning, and showering. It is also commonly installed before carbon filters, RO membranes, and UV systems because accumulated particles could clog these later treatment stages. However, a PP filter does not remove dissolved chemicals, minerals, or microorganisms by itself.

Granular Activated Carbon (GAC) Filter

A GAC filter contains loose granules of activated carbon, which look like small black grains. Their porous surfaces help reduce chlorine, certain chemicals and organic contaminants, and substances that cause unpleasant tastes and odors.

GAC may also reduce certain disinfection by-products, including trihalomethanes (THMs). Long-term exposure to THMs may increase health risks.

When PP and GAC cartridges are used together with an already treated municipal supply, the filtered water can serve household applications such as showering, washing, and cleaning. Carbon filtration can also improve drinking and cooking water by reducing chlorine, unpleasant tastes, and odors.

Chlorine, Taste, and Odor (CTO) Filter

A CTO filter uses activated carbon compressed into a solid block and generally provides finer filtration than a GAC filter. Its denser structure allows it to filter out even smaller particles while reducing chlorine, certain chemical contaminants, and unpleasant tastes and odors.

CTO filters are commonly used in drinking-water systems to improve water for drinking, cooking, and beverage preparation. They may also serve as a finer carbon filtration stage before the water reaches an RO membrane.

Reverse Osmosis (RO) Membrane

An RO membrane is commonly made from a thin-film composite material with an ultrathin polyamide filtering layer. It provides a much finer level of filtration than the preceding cartridges. Under pressure, water passes through this semipermeable membrane, while many dissolved substances and contaminants are rejected.

Depending on the system design and its verified reduction claims, RO can reduce total dissolved solids (TDS), salts, certain heavy metals, and various dissolved contaminants . It is commonly used for household drinking and cooking water when testing identifies high salinity or dissolved contaminants that sediment and activated carbon filters cannot adequately reduce.

Post-Carbon Filter

A post-carbon filter is installed after the main filtration stages, often after the storage tank in an RO system. It provides a final polishing stage by reducing any remaining unpleasant taste or odor before the water reaches the faucet.

Because its main purpose is to improve the final sensory quality of the water, it is particularly relevant to drinking, cooking, and beverage preparation. It should not be treated as the primary stage for removing sediment, microorganisms, or dissolved contaminants.

Choose the Right Water Filter Type for Your Intended Use

Water filters differ in the range of water they treat. A point-of-use filter serves a specific outlet, whereas a point-of-entry filter treats water throughout the property.

Point-of-Use (POU) Filters

A POU filter is installed at a specific water outlet, such as a faucet or an under-sink water line. It is commonly used when filtered water is primarily needed for drinking and cooking in the kitchen. Common examples include countertop water filters and under-sink water filters.

Point-of-Entry (POE)

A whole-house filter, also known as a point-of-entry (POE) system, is installed where the main water supply enters the building. This allows water to be filtered before it reaches faucets, showers, and water-using appliances. It is suitable for homes and buildings that need to improve the overall quality of water used throughout the property.

Consider the Maintenance Requirements

Regular maintenance helps a water filter maintain its flow rate and filtration effectiveness. Overused cartridges may become clogged, allow contaminants to pass through, or contribute to microbial growth within the system. Before choosing a filter, consider how often the cartridges should be changed, how easily they can be replaced, and whether replacement parts are readily available.

Filter Replacement Frequency

Replacement frequency depends on the cartridge type, incoming water quality, water consumption, cartridge capacity, and system design. Different cartridges have different capacities and recommended replacement intervals. In a multi-stage system, replacing the prefilters on time helps prevent clogging and protects the more expensive components downstream.

Ease of Maintenance

Ease of maintenance depends on both the system design and the available installation space. Before choosing a system, measure the intended area. Check that there is enough room to open the housing, remove the cartridges, and inspect the connections. A system that is easy to service in one home may not suit a smaller or less accessible space.

Tool-free housings and quick-change cartridges can make replacement easier. Pressure gauges, filter-life indicators, and replacement reminders can also help users identify when maintenance is needed.

Check Relevant Certifications

To protect users’ health and safety, check whether a water filter has been tested and certified to applicable standards. Certifications can help confirm that the product meets recognized requirements for material safety, contaminant reduction, and product quality. They are especially useful when comparing filters with similar specifications.

NSF Certification

NSF certification is widely recognized in the water filtration industry. The applicable NSF/ANSI standard depends on the type of product and the claims being made.

NSF/ANSI 42 covers aesthetic water quality concerns, such as chlorine, unpleasant tastes, and odors. NSF/ANSI 58 applies specifically to reverse osmosis systems and covers requirements such as material safety, structural integrity, and contaminant reduction performance. NSF/ANSI 61 addresses the health effects of materials and components that come into contact with drinking water.

CE Marking

The CE marking indicates that the manufacturer has assessed the product and declared that it complies with applicable EU requirements related to safety, health, and environmental protection. For water filtration systems containing electrical components, these standards may cover areas such as electrical safety and electromagnetic compatibility. CE is a conformity marking rather than a water filtration certification, so it does not by itself verify the removal of specific contaminants.

Regional Certifications

Some countries or regions require additional certifications before water filtration products can be installed or sold. In Australia, for example, relevant plumbing products may need certification under the WaterMark Certification Scheme and may be assessed against an applicable WaterMark Technical Specification, or WMTS. Users should therefore check the requirements of the market where the filter will be used.

Conclusion

Choosing a water filter requires matching the incoming water quality and intended use with a suitable filtration method, system type, maintenance plan, and relevant certifications. Lan Shan offers water filtration systems with one to five stages for residential, commercial, and industrial applications. This range allows brands, distributors, and wholesale buyers to build product portfolios for different water conditions and end-user needs.

Lan Shan also offers quick-change cartridge designs to simplify routine filter replacement. Selected products meet requirements including NSF/ANSI 42 58 61, EN 55014 and EN 60335 under CE marking, and WaterMark AS/NZS 3497:2021. Contact Lan Shan to discuss suitable product configurations, target-market requirements, and wholesale orders.